US20180265370A1 - Controlled process for precipitating calcium carbonate and vaterite precipitated calcium carbonate compositions formed by said process - Google Patents

Controlled process for precipitating calcium carbonate and vaterite precipitated calcium carbonate compositions formed by said process Download PDF

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US20180265370A1
US20180265370A1 US15/543,635 US201615543635A US2018265370A1 US 20180265370 A1 US20180265370 A1 US 20180265370A1 US 201615543635 A US201615543635 A US 201615543635A US 2018265370 A1 US2018265370 A1 US 2018265370A1
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Prior art keywords
pcc
calcium carbonate
vaterite
carbonate
gypsum
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Inventor
Christopher Paynter
Kalena STOVALL
Douglas Wicks
Gavin BUTLER-LEE
Parvin GOLBAYANI
Nigel Victor JARVIS
Graham M. Pring
David Taylor
Ricardo M. PEREZ
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Imerys Pigments Inc
Imerys USA Inc
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Imerys Pigments Inc
Imerys USA Inc
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Priority to US15/543,635 priority Critical patent/US20180265370A1/en
Assigned to IMERYS PIGMENTS, INC. reassignment IMERYS PIGMENTS, INC. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: PAYNTER, CHRISTOPHER, TAYLOR, DAVID, WICKS, DOUGLAS, PEREZ, RICARDO M., STOVALL, Kalena, BUTLER-LEE, Gavin, JARVIS, NIGEL VICTOR, PRING, GRAHAM M., GOLBAYANI, Parvin
Assigned to IMERYS USA, INC. reassignment IMERYS USA, INC. MERGER (SEE DOCUMENT FOR DETAILS). Assignors: IMERYS PIGMENTS, INC.
Publication of US20180265370A1 publication Critical patent/US20180265370A1/en
Abandoned legal-status Critical Current

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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
    • C01F11/00—Compounds of calcium, strontium, or barium
    • C01F11/18—Carbonates
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/46—Removing components of defined structure
    • B01D53/48—Sulfur compounds
    • B01D53/50—Sulfur oxides
    • B01D53/501—Sulfur oxides by treating the gases with a solution or a suspension of an alkali or earth-alkali or ammonium compound
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
    • C01F11/00—Compounds of calcium, strontium, or barium
    • C01F11/18—Carbonates
    • C01F11/181—Preparation of calcium carbonate by carbonation of aqueous solutions and characterised by control of the carbonation conditions
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
    • C01F11/00—Compounds of calcium, strontium, or barium
    • C01F11/18—Carbonates
    • C01F11/182—Preparation of calcium carbonate by carbonation of aqueous solutions and characterised by an additive other than CaCO3-seeds
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
    • C01F11/00—Compounds of calcium, strontium, or barium
    • C01F11/18—Carbonates
    • C01F11/182—Preparation of calcium carbonate by carbonation of aqueous solutions and characterised by an additive other than CaCO3-seeds
    • C01F11/183—Preparation of calcium carbonate by carbonation of aqueous solutions and characterised by an additive other than CaCO3-seeds the additive being an organic compound
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
    • C01F11/00—Compounds of calcium, strontium, or barium
    • C01F11/18—Carbonates
    • C01F11/185—After-treatment, e.g. grinding, purification, conversion of crystal morphology
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
    • C01F11/00—Compounds of calcium, strontium, or barium
    • C01F11/46—Sulfates
    • C01F11/464—Sulfates of Ca from gases containing sulfur oxides
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
    • C01F11/00—Compounds of calcium, strontium, or barium
    • C01F11/46—Sulfates
    • C01F11/468—Purification of calcium sulfates
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
    • C01F5/00—Compounds of magnesium
    • C01F5/24—Magnesium carbonates
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
    • C01F5/00—Compounds of magnesium
    • C01F5/40—Magnesium sulfates
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B14/00—Use of inorganic materials as fillers, e.g. pigments, for mortars, concrete or artificial stone; Treatment of inorganic materials specially adapted to enhance their filling properties in mortars, concrete or artificial stone
    • C04B14/02—Granular materials, e.g. microballoons
    • C04B14/26—Carbonates
    • C04B14/28—Carbonates of calcium
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K3/00—Use of inorganic substances as compounding ingredients
    • C08K3/18—Oxygen-containing compounds, e.g. metal carbonyls
    • C08K3/24—Acids; Salts thereof
    • C08K3/26—Carbonates; Bicarbonates
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09C—TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES ; PREPARATION OF CARBON BLACK  ; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS
    • C09C1/00—Treatment of specific inorganic materials other than fibrous fillers; Preparation of carbon black
    • C09C1/02—Compounds of alkaline earth metals or magnesium
    • C09C1/021—Calcium carbonates
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
    • D21H17/63—Inorganic compounds
    • D21H17/67—Water-insoluble compounds, e.g. fillers, pigments
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
    • D21H17/63—Inorganic compounds
    • D21H17/67—Water-insoluble compounds, e.g. fillers, pigments
    • D21H17/675—Oxides, hydroxides or carbonates
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2251/00—Reactants
    • B01D2251/40—Alkaline earth metal or magnesium compounds
    • B01D2251/404—Alkaline earth metal or magnesium compounds of calcium
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2251/00—Reactants
    • B01D2251/60—Inorganic bases or salts
    • B01D2251/606—Carbonates
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/46—Removing components of defined structure
    • B01D53/48—Sulfur compounds
    • B01D53/50—Sulfur oxides
    • B01D53/501—Sulfur oxides by treating the gases with a solution or a suspension of an alkali or earth-alkali or ammonium compound
    • B01D53/502—Sulfur oxides by treating the gases with a solution or a suspension of an alkali or earth-alkali or ammonium compound characterised by a specific solution or suspension
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2002/00—Crystal-structural characteristics
    • C01P2002/70—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
    • C01P2002/76—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data by a space-group or by other symmetry indications
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/01—Particle morphology depicted by an image
    • C01P2004/03—Particle morphology depicted by an image obtained by SEM
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/51—Particles with a specific particle size distribution
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/60—Particles characterised by their size
    • C01P2004/61—Micrometer sized, i.e. from 1-100 micrometer
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
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    • C01P2004/60—Particles characterised by their size
    • C01P2004/62—Submicrometer sized, i.e. from 0.1-1 micrometer
    • C—CHEMISTRY; METALLURGY
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    • C01P2006/80—Compositional purity
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K3/00—Use of inorganic substances as compounding ingredients
    • C08K3/18—Oxygen-containing compounds, e.g. metal carbonyls
    • C08K3/24—Acids; Salts thereof
    • C08K3/26—Carbonates; Bicarbonates
    • C08K2003/265—Calcium, strontium or barium carbonate

Definitions

  • the present disclosure relates to a controlled process for converting gypsum into a precipitated calcium carbonate having desired polymorph and crystal size characteristics as well as precipitated calcium carbonate compositions formed by the controlled process.
  • a power plant is an industrial facility for the generation of electric power.
  • Each power station contains one or more generators, a rotating machine that converts mechanical power into electrical power by creating relative motion between a magnetic field and a conductor.
  • the energy source harnessed to turn the generator varies widely.
  • Most power stations in the world burn fossil fuels such as coal, oil, and natural gas to generate electricity.
  • Fossil fuel power plants are commonly coal-fired power stations. These coal powered plants produce heat by burning coal in a steam boiler. The steam drives a steam turbine and generator that then produces electricity.
  • a biomass-fueled power plant may be fueled by waste from sugar cane, municipal solid waste, landfill methane, or other forms of biomass.
  • the waste products from these processes include ash, sulfur dioxide, nitrogen oxides and carbon dioxide. Some of the gases can be removed from the waste stream to reduce pollution.
  • Flue gas is the gas exiting to the atmosphere via a flue, which is a pipe or channel for conveying exhaust gases from a fireplace, oven, furnace, boiler or steam generator. Quite often, the flue gas refers to the combustion exhaust gas produced at power plants.
  • the removal of waste products from flue gas, such as SO 2 is mandated by air quality regulatory agencies to reduce the acid rain caused by coal burning.
  • the post-combustion flue gas is treated with limestone that sequesters the SO 2 in the form of gypsum (e.g. calcium sulfate).
  • FGD flue gas desulfurization
  • Gypsum resulting from the FGD of coal fired power plants is an impure form of calcium sulfate.
  • These impurities may have a major impact on the quality and polymorph of precipitated calcium carbonate obtained when the gypsum is reacted with carbonates.
  • Magnesium sulfate, for example, is a co-product with the gypsum from the FGD process and is problematic as its high water solubility increases the difficulty of cleaning up the FGD process water. Overcoming these effects would be advantageous in providing a consistent industrial calcium carbonate.
  • one aspect of the present disclosure relates to precipitated calcium carbonate compositions with desired polymorph and crystal size and a controlled process for converting gypsum into said precipitated calcium carbonate while avoiding the aforementioned disadvantages.
  • fluids may be used for a variety of reasons, such as lubrication and cooling of drill bit cutting surfaces while drilling, controlling formation fluid pressure to prevent blowouts, maintaining well stability, suspending solids in the well, minimizing fluid loss into and stabilizing the formation through which the well is being drilled, fracturing the formation in the vicinity of the well, displacing the fluid within the well with another fluid, cleaning the well, testing the well, emplacing a packer, abandoning the well or preparing the well for abandonment, and otherwise treating the well or the formation.
  • weighting agents to increase specific gravity of the mud
  • generally finely ground barites barium sulfate ore
  • transport clay and other substances capable of adhering to and coating the borehole surface may have undesirable properties.
  • the weighting agents such as iron oxide-based weighting agents may be overly abrasive and can cause damage or corrosion to well equipment.
  • barium sulfate agents may fill cracks in the well formation, thereby inhibiting flow of the hydrocarbon to be extracted. It may be desirable, therefore, to provide improved additives, such as weighting agents, with improved properties.
  • the present disclosure relates to a precipitated calcium carbonate having a vaterite polymorph that meets at least one of the following: (i) a stearic acid uptake surface area ranging from 5 to 75 m 2 /g, or (ii) a cubicity ranging from 0.03 to 30, or (iii) a squareness ranging from 70 to 110°, or (iv) an aspect ratio ranging from 1 to 20.
  • the precipitated calcium carbonate having a vaterite polymorph also has a BET surface area ranging from 5-75 m 2 /g.
  • the precipitated calcium carbonate having a vaterite polymorph also has a d 50 particle size ranging from 0.1 to 30 ⁇ m.
  • the precipitated calcium carbonate having a vaterite polymorph also has a d 90 particle size ranging from 2 to 25 ⁇ m.
  • the precipitated calcium carbonate having a vaterite polymorph also has a d 10 particle size ranging from 0.1 to 4 ⁇ m.
  • the precipitated calcium carbonate having a vaterite polymorph also has a steepness (100 ⁇ d 30 /d 70 ) ranging from 30 to 100.
  • the precipitated calcium carbonate having a vaterite polymorph also has an ISO brightness ranging from 54-97.
  • the precipitated calcium carbonate having a vaterite polymorph also has a DIN yellow index ranging from 0.7 to 10.3.
  • the precipitated calcium carbonate having a vaterite polymorph additionally comprises at least one polymorph selected from the group consisting of calcite, aragonite, and amorphous calcium carbonate.
  • the precipitated calcium carbonate having a vaterite polymorph further comprises an active ingredient, encapsulated, absorbed, adsorbed, or embedded onto or into the vaterite polymorph for use in delivering the active ingredient to a delivery site.
  • the present disclosure relates to a precipitated calcium carbonate, comprising a vaterite polymorph and at least one impurity by weight relative to the total weight of the precipitated calcium carbonate selected from the group consisting of (i) Fe greater than 0.04 wt %, (ii) NH 4 OH ranging from 0 to 35 wt %, (iii) (NH 4 ) 2 CO 3 ranging from 0 to 40 wt %, (iv) (NH 4 ) 2 SO 4 ranging from 0 to 35 wt %, (v) CaSO 4 ranging from 10 to 50 wt %, (vi) MgCO 3 ranging from 2 to 50 wt %, and (vii) CaO ranging from 5 to 10 wt %.
  • a precipitated calcium carbonate comprising a vaterite polymorph and at least one impurity by weight relative to the total weight of the precipitated calcium carbonate selected from the group consisting of (i) Fe greater than 0.04 wt %
  • the precipitated calcium carbonate also has a BET surface area ranging from 5 to 75 m 2 /g.
  • the precipitated calcium carbonate also has a stearic acid uptake surface area ranging from 5 to 75 m 2 /g.
  • the precipitated calcium carbonate also has a d 50 particle size ranging from 0.1 to 30 ⁇ m.
  • the precipitated calcium carbonate also has a do particle size ranging from 2 to 25 ⁇ m.
  • the precipitated calcium carbonate also has a d 10 particle size ranging from 0.1 to 4 ⁇ m.
  • the precipitated calcium carbonate also has a steepness (100 ⁇ d 30 /d 70 ) ranging from 30 to 100.
  • the precipitated calcium carbonate also has an ISO brightness ranging from 54 to 97.
  • the precipitated calcium carbonate also has a DIN yellow index ranging from 0.7 to 10.3.
  • the precipitated calcium carbonate additionally comprises at least one polymorph selected from the group consisting of calcite, aragonite, and amorphous calcium carbonate.
  • the present disclosure relates to a precipitated calcium carbonate having a vaterite polymorph, which emits an amount of carbon dioxide during production that is less than an amount of carbon dioxide emitted during the production of a precipitated calcium carbonate having a vaterite polymorph produced by calcining and slaking natural calcium carbonate.
  • the precipitated calcium carbonate having a vaterite polymorph has a BET surface area ranging from 5-75 m 2 /g.
  • the precipitated calcium carbonate having a vaterite polymorph has a stearic acid uptake surface area ranging from 5-75 m 2 /g.
  • the precipitated calcium carbonate having a vaterite polymorph has a d 50 particle size ranging from 0.1 to 30 ⁇ m.
  • the precipitated calcium carbonate having a vaterite polymorph has a d 90 particle size ranging from 2 to 25 ⁇ m.
  • the precipitated calcium carbonate having a vaterite polymorph has a d 10 particle size ranging from 0.1 to 4 ⁇ m.
  • the precipitated calcium carbonate having a vaterite polymorph has a steepness (100 ⁇ d 30 /d 70 ) ranging from 30 to 100.
  • the precipitated calcium carbonate having a vaterite polymorph has an ISO brightness ranging from 54-97.
  • the precipitated calcium carbonate having a vaterite polymorph has a DIN yellow index ranging from 0.7 to 10.3.
  • the precipitated calcium carbonate having a vaterite polymorph additionally comprises at least one polymorph selected from the group consisting of calcite, aragonite, and amorphous calcium carbonate.
  • the present disclosure relates to a precipitated calcium carbonate having a low carbon footprint comprising a vaterite calcium carbonate polymorph and a first amount of Fe, wherein the first amount of Fe is inversely correlated to carbon dioxide emissions, and wherein the first amount of Fe is greater than a second amount of Fe present in a precipitated calcium carbonate produced by calcining and slaking natural calcium carbonate.
  • the first amount of Fe is greater than 0.04 wt % relative to the total weight of the precipitated calcium carbonate having a low carbon footprint.
  • the precipitated calcium carbonate having a low carbon footprint has a BET surface area ranging from 5-75 m 2 /g.
  • the precipitated calcium carbonate having a low carbon footprint has a stearic acid uptake surface area ranging from 5-75 m 2 /g.
  • the precipitated calcium carbonate having a low carbon footprint has a d 50 particle size ranging from 0.1 to 30 ⁇ m.
  • the precipitated calcium carbonate having a low carbon footprint has a d 90 particle size ranging from 2 to 25 ⁇ m.
  • the precipitated calcium carbonate having a low carbon footprint has a d 10 particle size ranging from 0.1 to 4 ⁇ m.
  • the precipitated calcium carbonate having a low carbon footprint has a steepness (100 ⁇ d 30 /d 70 ) ranging from 30 to 100.
  • the precipitated calcium carbonate having a low carbon footprint has an ISO brightness ranging from 54-97.
  • the precipitated calcium carbonate having a low carbon footprint has a DIN yellow index ranging from 0.7 to 10.3.
  • the precipitated calcium carbonate having a low carbon footprint additionally comprises at least one polymorph selected from the group consisting of calcite, aragonite, and amorphous calcium carbonate.
  • the present disclosure relates to a paper product, comprising a precipitated calcium carbonate having a vaterite polymorph, in one or more of its embodiments, wherein the precipitated calcium carbonate is present in the paper product as a filler or as a coating.
  • the paper product is a paper towel, an absorbent cloth, or a sanitary napkin.
  • the present disclosure relates to a polymer comprising a polymeric material and a filler, wherein the filler comprises a precipitated calcium carbonate having a vaterite polymorph, in one or more of its embodiments.
  • the polymer is biodegradable.
  • the present disclosure relates to a stable vaterite product, wherein less than 1% conversion of the vaterite to another polymorph occurs over a period of at least one day.
  • FIG. 1 is an illustration of a flue gas desulfurizing apparatus.
  • FIG. 2 is an SEM image of a rhombic calcite, 300-500 nm.
  • FIG. 3 is an SEM image of a calcite and vaterite blend.
  • FIG. 4 is an SEM image of a rhombic calcite, ⁇ 5 ⁇ m.
  • FIG. 5 is an SEM image of a vaterite and aragonite blend.
  • FIG. 6 is an SEM image of vaterite.
  • FIG. 7 is an SEM image of a vaterite and calcite blend produced from gypsum and sodium carbonate.
  • FIG. 8 is an SEM image of a rhombic calcite, 300-500 nm from calcite-seeded gypsum.
  • FIG. 9 is an SEM image of a rhombic calcite, 1-3 ⁇ m from dolomite seeded-gypsum.
  • FIG. 10 is an SEM image of a rhombic calcite, 5 ⁇ m from calcite seeded-gypsum.
  • FIG. 11 is an SEM image of a rhombic calcite, 300 nm-1 ⁇ m from magnesite-seeded gypsum.
  • FIG. 12 is an SEM image of a calcite ⁇ 300-500 nm with 2% calcite seeding and low theoretical ammonium bicarbonate content in ammonium carbonate.
  • FIG. 13 is an SEM image of a vaterite ⁇ 300-500 nm with no seeding and low theoretical ammonium bicarbonate content in ammonium carbonate.
  • FIG. 14 is an SEM image of a calcite ⁇ 300-500 nm with 2% calcite seeding and high theoretical ammonium bicarbonate content in ammonium carbonate.
  • FIG. 15 is an SEM image of a Rhombic PCC from Crystal Seeding with calcite seed.
  • FIG. 16 is an SEM image of a Rhombic PCC from Crystal Seeding with magnesite seed.
  • FIG. 17 is an SEM image of a Rhombic PCC from Crystal Seeding with dolomite seed.
  • FIG. 18 is an SEM image of a Non-Rhombic Polymorph from Partial-Crystal Seeding of vaterite+aragonite from [calcite+MgCO 3 (1:3 molar ratio)] seeding.
  • FIG. 19 is an SEM image of a Non-Rhombic Polymorph from Non-Crystal Seeding of vaterite+aragonite from MgCO 3 seeding.
  • FIG. 20 is an SEM image of a Non-Rhombic Polymorph from Non-Crystal Seeding of vaterite rhombic calcite and aragonite from dolomitic quicklime seeding.
  • FIG. 21 is an SEM image of a Calcite, Vaterite from FGD Gypsum+Ammonium Carbonate.
  • FIG. 22 is an SEM image of a Jamaican ore Seed GCC.
  • FIG. 23 is an SEM image of a Rhombic Calcite from Calcite-Seeded Gypsum.
  • FIG. 24 is an SEM image of a bluegrass ore Dolomite Seed GCC.
  • FIG. 25 is an SEM image of a Rhombic Calcite from Dolomite-Seeded Gypsum.
  • FIG. 26 is an SEM image of a Vaterite from Pure Gypsum (No Seeding) at Low Temp (12 C).
  • FIG. 27 is an SEM image of a Calcite, Vaterite Blend from Pure Gypsum (No Seeding).
  • FIG. 28 is an SEM image of a Rhombic Calcite from Calcite-Seeded Gypsum.
  • FIG. 29 is an SEM image of a Large Rhombic Calcite from Calcite-Seeded Gypsum Reacted with Ammonium Carbonate Heated >46 C.
  • FIG. 30 is an SEM image of a Vaterite, Aragonite from Gypsum seeded with MgCO 3 .
  • FIG. 31 is an SEM image of MgCO 3 from MgSO 4 +Ammonium Carbonate.
  • FIG. 32 is an SEM image of MgCO 3 from MgSO 4 +Ammonium Carbonate.
  • FIG. 33 is an SEM image of a Carbonate Blend (est ⁇ 7.3% MgCO 3 , 22.4% MgCa(CO 3 ) 2 and 61.8% CaCO 3 ) from 1:1 [CaSO 4 :MgSO 4 ]+Ammonium Carbonate.
  • FIG. 34 is an SEM image of MgCO 3 from MgSO 4 +Sodium Carbonate.
  • FIG. 35 is an SEM image of a Vaterite, Calcite from Gypsum+Sodium Carbonate.
  • FIG. 36 is an SEM image of Gypsum, 99% (Sigma Gypsum) Used for Most Trials (Except Where Noted).
  • FIG. 37 is an SEM image of a US Gypsum.
  • FIG. 38 is an SEM image of a US Gypsum.
  • FIG. 39 shows SEM images of vaterite to calcite conversion for various feed concentrations and aging processes.
  • FIG. 40 shows SEM images for different feed concentrations.
  • FIG. 41 shows an SEM image and an exemplary measurement of squareness.
  • the present disclosure relates to a process for desulfurizing a flue gas comprising i) scrubbing a flue gas comprising sulfur dioxide with a SO 2 sequestrating agent to yield a suspension comprising flue gas desulfurized gypsum and an aqueous solution comprising magnesium sulfate ii) separating the flue gas desulfurized gypsum from the magnesium sulfate solution iii) reacting at least one carbonate salt with the magnesium sulfate solution to yield magnesium carbonate, which may be of the form magnesite and iv) isolating the magnesium carbonate or magnesite.
  • the flue gas for desulfurization is obtained from a coal power plant, an oil power plant, a natural gas power plant, and/or a biomass fueled plant.
  • Calcium carbonate used in the flue gas desulfurization process can be pure calcium carbonate or have added components, such as magnesium. Depending on the calcium and magnesium levels, calcium carbonate may be classified as calcite or dolomite, among others.
  • Dolomite is an anhydrous carbonate mineral composed of calcium magnesium carbonate, e.g. CaMg(CO 3 ) 2 .
  • the word dolomite is also used to describe the sedimentary carbonate rock, which is composed predominantly of the mineral dolomite.
  • the mineral dolomite crystallizes in the trigonal-rhombohedral system. It forms white, tan, gray, or pink crystals.
  • Dolomite is a double carbonate, having an alternating structural arrangement of calcium and magnesium ions.
  • magnesite may refer to the crystalline form or the amorphous form of magnesium carbonate, MgCO 3 .
  • the SO 2 sequestrating agent can be, but is not limited to, calcium-containing carbonate minerals including dolomite, calcite, vaterite, aragonite, ankerite, huntite, minrecordite, barytocite, ikaite, amorphous calcium carbonate, hydrates thereof, or combinations thereof.
  • the SO 2 sequestrating agent is dolomite, or a hydrate thereof.
  • the SO 2 sequestrating agent is vaterite of high surface area.
  • the magnesium sulfate rich supernatant of a spent carbonate stream is separated from the solid gypsum co-product by any conventional means, such as filtration or centrifugation, and optionally recrystallizing the solid gypsum to obtain a product with a higher purity.
  • Filtration methods may be, but are not limited to, vacuum filtration.
  • the purity of isolated desulfurized gypsum may be variable, depending on the starting purity of the sulfur-containing flue gas.
  • a magnesium sulfate solution from the extraction of dolomite may be seeded with gypsum and/or a carbonate (such as calcium carbonate) to control the dolomite composition.
  • gypsum and/or a carbonate (such as calcium carbonate) to control the dolomite composition.
  • a carbonate such as calcium carbonate
  • increasing the relative amount of gypsum may decrease dolomite precipitation, whereas relatively more ammonium carbonate may increase dolomite precipitation.
  • the carbonate salt comprises a carbonate or bicarbonate anion and at least one cation selected from the group consisting of sodium, calcium, cobalt, copper, potassium, ammonium, chromium, iron, aluminum, tin, lead, magnesium, silver, titanium, vanadium, zinc, lithium, nickel, barium, strontium, and hydronium.
  • the added carbonate salt may be in solid form, in aqueous solution, or a suspension or slurry. Under conditions which the carbonate salt is added as a solution or suspension, the pH of the solution or suspension may be acidic (pH less than 6.5), neutral (pH 6.5-7.5), or basic (pH greater than 7.5).
  • Magnesite is a mineral with the chemical formula MgCO 3 (magnesium carbonate).
  • Naturally occurring magnesite generally is a trigonal-hexagonal scalenohedral crystal system. Similar to the production of lime, magnesite can be burned in the presence of charcoal to produce MgO, which in the form of a mineral is known as periclase. Large quantities of magnesite are burnt to make magnesium oxide, which is a refractory material used as a lining in blast furnaces, kilns and incinerators. Magnesite can also be used as a binder in flooring material. Furthermore it is being used as a catalyst and filler in the production of synthetic rubber and in the preparation of magnesium chemicals and fertilizers.
  • the isolated magnesite from the present disclosure has value as a filler pigment especially for applications which require some degree of acid resistance (food packaging, synthetic marble).
  • the isolated magnesite may be amorphous with a surface area greater than 20 m 2 /g.
  • the flue gas desulfurized gypsum is separated from the magnesium sulfate solution by filtration or centrifugation.
  • the gypsum isolated by filtration or centrifugation can optionally be 1) used in the manufacture of wall board or other construction materials, 2) landfilled, or 3) converted into calcium carbonate by known processes in the prior art or by processes disclosed hereinafter.
  • the gypsum for use in the present disclosure, there is no particular limitation and the gypsum may be natural gypsum, synthetic (e.g., chemically produced) gypsum, FGD gypsum, and/or phosphogypsum. However, FGD gypsum and chemically produced gypsum are mentioned as examples.
  • the FGD gypsum may be ground or milled.
  • the grinding or milling of the FGD gypsum may be followed by one or more of magnetic separation, bleaching, acid washing, or other beneficiation processes.
  • gypsum is a soft sulfate mineral composed of calcium sulfate dihydrate, with the chemical formula CaSO 4 .2H 2 O. It can be used as a fertilizer, is the main constituent in many forms of plaster and is widely mined. Gypsum resulting from the flue gas desulfurization (FGD) of coal fired power plants is an impure form of calcium sulfate. When converted into calcium carbonate, these impurities may have a major impact on the quality and polymorph of precipitated calcium carbonate obtained when the gypsum is reacted with ammonium sulfate.
  • FGD flue gas desulfurization
  • Magnesium sulfate for example, is a co-product with the gypsum from the FGD process and is problematic as its high water solubility increases the difficulty of cleaning up the FGD process water.
  • US gypsum refers to impure gypsum, which generally is 80-90% pure. This gypsum typically contains impurities such as calcite and MgCO 3 and these impurities may be in about a 1:3 ratio.
  • Raw gypsum, or non-purified gypsum may have variable purity depending on the source.
  • precipitated calcium carbonate refers to a synthetically manufactured calcium carbonate material that can be tailor-made with respect to its compositional forms, purity, morphology, particle size, and other characteristics (e.g. particle size distribution, surface area, cubicity, etc.) using various precipitation techniques and methods.
  • Precipitated calcium carbonate thus differs from natural calcium carbonate or natural calcium carbonate-containing minerals (marble, limestone, chalk, dolomite, shells, etc.) or ground calcium carbonate (natural calcium carbonate which has been ground) in terms of both methods of manufacture as well as the various compositions/characteristics mentioned above, and which will be described more fully hereinafter.
  • the method of producing precipitated calcium carbonate (PCC) by use of calcined natural calcium carbonate is well-known and widely used in the industry. Calcining generates calcium oxide from which a precipitated calcium carbonate is produced upon consecutive exposure to water and carbon dioxide. However, the energy consumed in calcining natural calcium carbonate is a large part of the production cost. Therefore, converting impure FGD gypsum, a bulk byproduct from power plant energy production, or other non-calcined gypsum sources into PCC would provide a low energy and economical method for PCC manufacture.
  • the present disclosure relates to a process for converting gypsum into precipitated calcium carbonate without a calcination step, and controlling the morphology, size, and properties of the precipitated calcium carbonate thus obtained.
  • vaterite, calcite, aragonite, amorphous, or a combination thereof can be precipitated from aqueous solution in one or more different compositional forms: vaterite, calcite, aragonite, amorphous, or a combination thereof.
  • vaterite, calcite, and aragonite are crystalline compositions and may have different morphologies or internal crystal structures, such as, for example, rhombic, orthorhombic, hexagonal, scalenohedral, or variations thereof.
  • Vaterite is a metastable phase of calcium carbonate at ambient conditions at the surface of the earth and belongs to the hexagonal crystal system.
  • Vaterite is less stable than either calcite or aragonite, and has a higher solubility than either of these phases. Therefore, once vaterite is exposed to water, it may convert to calcite (e.g., at low temperature) or aragonite (at high temperature: ⁇ 60° C.).
  • the vaterite form is uncommon because it is generally thermodynamically unstable.
  • the calcite form is the most stable form and the most abundant in nature and may have one or more of several different shapes, for example, rhombic and scalenohedral shapes.
  • the rhombic shape is the most common and may be characterized by crystals having approximately equal lengths and diameters, which may be aggregated or unaggregated.
  • Calcite crystals are commonly trigonal-rhombohedral.
  • Scalenohedral crystals are similar to double, two-pointed pyramids and are generally aggregated.
  • the aragonite form is metastable under ambient temperature and pressure, but converts to calcite at elevated temperatures and pressures.
  • the aragonite crystalline form may be characterized by acicular, needle- or spindle-shaped crystals, which are generally aggregated and which typically exhibit high length-to-width or aspect ratios.
  • aragonite may have an aspect ratio ranging from about 3:1 to about 15:1.
  • Aragonite may be produced, for example, by the reaction of carbon dioxide with slaked lime.
  • the methods of producing a PCC composition may be varied to yield different polymorphs of calcium carbonate, such as, for example, vaterite, calcite, aragonite, amorphous calcium carbonate, or combinations thereof.
  • the methods may be modified by varying one or more of the reaction rate, the pH of the mixtures, the reaction temperature, the carbonate species present in the reaction (e.g., ammonium carbonate, ammonium bicarbonate), the concentration of the different carbonate species present in the reaction (e.g., ammonium carbonate and/or ammonium bicarbonate concentrations), the purity of the feed materials (e.g., purity of the feed gypsum), and the concentrations of the feed materials (e.g., gypsum and/or carbonate concentrations and/or seeds and other additives).
  • the reaction rate e.g., the pH of the mixtures, the reaction temperature, the carbonate species present in the reaction (e.g., ammonium carbonate, ammonium bicarbonate), the concentration
  • Methods A-I converting gypsum into precipitated calcium carbonate is accomplished with Methods A-I, or a combination thereof.
  • Method and process parameter selection enables control of the precipitated calcium carbonate structure, such as crystalline polymorph and particle size.
  • the following is a general description of the Methods A-I.
  • the method includes:
  • the amount of mineral acid added to the FGD gypsum is optionally a molar equivalent of or in excess of the amount of unreacted carbonate.
  • the method includes:
  • the amount of mineral acid added to the FGD gypsum is equimolar to the amount of unreacted carbonate.
  • calcite or aragonite
  • the calcite can be rhombohedral or scalenohedral.
  • the method includes:
  • the method includes:
  • the seed may result in a hybrid morphology having morphologies related to both the seed morphology and the PCC morphology.
  • the method includes:
  • the method includes
  • ammonium carbonate comprises a mixture of ammonium carbonate, ammonium carbamate and ammonium bicarbonate, such that the amount of ammonium bicarbonate is greater than or equal to the ammonium carbamate concentration, and upon reaction yields a calcite or calcite-vaterite blend.
  • the method includes:
  • ammonium carbonate comprises a mixture of ammonium carbonate, ammonium carbamate and ammonium bicarbonate, such that the amount of ammonium bicarbonate is less than or equal to the ammonium carbamate concentration, and upon reaction yields a vaterite or vaterite-calcite blend.
  • the method includes:
  • the method includes:
  • Tables 1 and 2 below identify product characteristics obtained from various examples of the foregoing methods.
  • reaction may refer to any complete or partial reaction.
  • a partial reaction refers to any reaction where some amount of a reagent or substrate remains in the reaction mixture after the reaction takes place.
  • precipitation of the PCC may be influenced or controlled by one or more of the reaction rate, pH, the ionic strength, reaction temperature, carbonate species present in the reaction, seed species composition, seed species concentration, purity of the feed materials (e.g., gypsum), concentration of the feed materials, ratio of the feed materials, or aging of the reaction components.
  • the pH of the reacting mixture may be controlled.
  • the reacting mixture may be acidic (pH less than 6.5), neutral (pH 6.5-7.5), or basic (pH greater than 7.5).
  • the ionic strength of the reacting mixture may also be controlled.
  • the ionic strength, I, of a solution is a function of the concentration of all ions present in that solution.
  • the ionic strength is controlled by the stoichiometry of ionizable reactants.
  • the ionic strength is controlled by the addition of ionic additives. These ionic additives may be a participating reactant, a spectator ion (i.e. a non-participating reactant), and/or a total ionic strength adjustment buffer.
  • the ionic strength is controlled by the use of deionized (DI) water.
  • a solvent may be added to gypsum to form a gypsum solution, slurry or suspension prior to reacting with the carbonate source.
  • Suitable solvents that may be used for forming a gypsum solution, slurry, or suspension include aprotic polar solvents, polar protic solvents, and non-polar solvents.
  • Suitable aprotic polar solvents may include, but are not limited to, propylene carbonate, ethylene carbonate, butyrolactone, acetonitrile, benzonitrile, nitromethane, acetonitrile, nitrobenzene, sulfolane, dimethylformamide, N-methylpyrrolidone, or the like.
  • Suitable polar protic solvents may include, but are not limited to, water, nitromethane, and short chain alcohols.
  • Suitable short chain alcohols may include, but are not limited to, one or more of methanol, ethanol, propanol, isopropanol, butanol, or the like.
  • Suitable non-polar solvents may include, but are not limited to, cyclohexane, octane, heptane, hexane, benzene, toluene, methylene chloride, carbon tetrachloride, or diethyl ether. Co-solvents may also be used.
  • the solvent added to gypsum is water.
  • Gypsum is moderately water-soluble (2.0-2.5 g/l at 25° C.). Therefore, to form a gypsum solution, enough water is added to fully dissolve all of the gypsum prior to reaction. To form a slurry or suspension, an amount of water is added to partially dissolve the gypsum, such that some of the gypsum is fully dissolved and some of the gypsum remains in solid form. In another embodiment, water is added to gypsum to form a slurry, wherein the percent of solids in the slurry is 10-50%, 20-40%, or 30-35%. In methods A-I, the concentration of the reacting mixture is also controlled. In a certain embodiment, the concentration is controlled by the addition or subtraction of water from the reacting solution, mixture, or slurry.
  • the mineral acid, ammonium carbonate, calcite, aragonite, calcium carbonate, dolomite, ammonium bicarbonate, ammonium carbamate, ammonium hydroxide, carbon dioxide, or any other additive or combination thereof may be added to the gypsum in bulk, portion-wise, or by a slow-addition process to control the PCC product characteristics.
  • the rate of addition of these components also controls the reacting mixture concentration.
  • the mineral acid, ammonium carbonate, calcite, aragonite, calcium carbonate, dolomite, ammonium bicarbonate, ammonium carbamate, ammonium hydroxide, carbon dioxide, or any other additive or carbonate source or combination thereof is added as a solution, a solid, a suspension or slurry, a gas, or a neat liquid.
  • the gas may be bubbled into a solution to an effective concentration, or may be used to purge or pressurize the reaction vessel until a desired effective concentration is reached.
  • the carbonate source is selected from the group consisting of ammonium carbonate, ammonium bicarbonate, ammonium carbamate, calcium carbonate, dolomite, a metal carbonate, and carbon dioxide, wherein the metal carbonate comprises a carbonate or bicarbonate anion and at least one cation selected from the group consisting of sodium, calcium, cobalt, copper, potassium, ammonium, chromium, iron, aluminum, tin, lead, magnesium, silver, titanium, vanadium, zinc, lithium, nickel, barium, strontium, and hydronium.
  • water is added to the carbonate source to form a slurry prior to the reaction with gypsum.
  • the carbonate source slurry is then added to the gypsum to give a molar ratio of reaction of gypsum:carbonate source of 1:1.1 to 1:5, 1:1.3 to 1:2.5, or 1:1.5 to 1:2.
  • the carbonate selected should, after reaction with the gypsum, yield a sulfate product with higher solubility than the calcium carbonate generated. Therefore, the generated sulfate may be separated from the calcium carbonate precipitate by removal of the aqueous phase from the reaction slurry.
  • Exemplary metal carbonates include sodium carbonate and magnesium carbonate.
  • the sulfate product can be treated as needed, and used for an appropriate, separate application.
  • ammonium carbonate is used in the reaction
  • ammonium sulfate will be generated, which can be separated and used in applications such as fertilizer.
  • a portion can be fed into the starting gypsum slurry to aid in control of the reaction rate, and consequently, control the PCC produced.
  • the cake can be washed with water to remove remaining sulfate.
  • the carbonate source can be pre-formed or generated during the reaction. For example, CO 2 may be bubbled with ammonia gas to generate ammonium carbonate used for the reaction.
  • ammonium carbonate exists as a mixed salt comprising a mixture of ammonium carbonate, ammonium carbamate, and ammonium bicarbonate.
  • the amount of each species may depend on the reaction conditions used to manufacture the ammonium carbonate.
  • ammonium carbamate quickly converts to ammonium carbonate in the presence of water.
  • ammonium bicarbonate dissolves slower and reacts slower with gypsum than ammonium carbamate or ammonium carbonate.
  • the PCC production process of methods A-I of the present disclosure aims to produce only one form of PCC.
  • a small amount of an alternative polymorph is often present, and can be readily tolerated in most end uses.
  • the PCC compositions comprising mixtures of crystalline forms (e.g., aragonite and calcite) can be readily employed in coating formulations.
  • the compositions are likely to contain a small amount of at least one other crystal PCC structure (e.g., calcite).
  • the PCC compositions of the present disclosure may optionally comprise at least one second PCC form that differs from the main PCC form.
  • the size, surface area, and cubicity of the PCC products may be influenced by feed concentrations or aging of the reaction components.
  • a lower feed concentration may result in a larger particle size distribution.
  • a larger particle size distribution may have a lower surface area.
  • Aging for example, may reduce the surface area of the PCC or improve the cubicity of the PCC particles.
  • the aging may convert some or all of a polymorph to a different polymorph. For example, aging may convert a vaterite phase to calcite.
  • including ammonium sulfate in a gypsum slurry feed may aid in controlling the PCC polymorph and particle size.
  • a stage of drying the PCC product may also be carried out in any of methods A-I subsequent to dewatering.
  • the drying of the product may also contribute to the resulting crystal product polymorph.
  • the PCC reaction product is a first composition after the reaction, prior to drying, with a solids content of at least 70%.
  • the PCC reaction product may convert to a second composition after the drying stage.
  • the drying stage may convert any amorphous PCC product of a first composition to a crystalline polymorph of a second composition (and different drying methods may make different polymorphs).
  • the product of a first composition may be aged and seeded.
  • a dried product may also be aged. Similar to the drying process, aging may also change the polymorph composition.
  • the reaction to form PCC, the seeding, the drying, and the aging may all be employed in a batch process, or a continuous process (e.g. in a tubular reactor with inline static mixers or cascade mixers).
  • the drying is performed at a temperature range of 30-150° C. for 1-15 hours.
  • the addition of additives or seed materials may affect the structure of the PCC.
  • adding citric acid to the PCC formation step may increase the surface area of a formed PCC product.
  • Altering the pH, such as through the use of an acidic additive, such as an acid (e.g., phosphoric acid), may be used to control or vary the shape, particle size, or surface area of the PCC, and in particular to vary the morphology of a PCC.
  • the seed composition may be used to control the resulting PCC morphology.
  • using greater than about 5 wt % coarse scalenohedral PCC (relative to the weight of the feed material) as a seed material may yield a larger or coarser PCC product, and may result in a greater surface area.
  • using less than about 5% of a fine rhombohedral PCC as a seed material yields a PCC product with a finer crystal size within a PCC aggregate, whereas greater than about 5% of the fine rhombohedral PCC seed material yields a finer-sized aggregate of the PCC produced.
  • a “hybrid structure” refers to a PCC component bound to at least a portion of a surface of a seed component.
  • the PCC component may be chemically bound to the seed component, such as, for example, through ionic, coordinate covalent (dative), or van der Waals bonds.
  • the PCC component may physically bond or attach to the seed component.
  • the PCC component may be adsorbed or physisorbed to the seed component.
  • the PCC component may form a carbonate layer over the seed component during the carbonate addition step.
  • the PCC component may form a carbonate layer, shell, or coating that covers at least a portion of, majority of, or substantially all of the seed component.
  • the PCC component may coat, enclose, or encapsulate substantially all of the seed component.
  • the hybrid structure may include a PCC component, a seed component, and/or an interfacial component.
  • the interfacial component may be, for example, a boundary region between the PCC component and the seed component.
  • the interfacial component may include a chemical composition containing elements of the carbonate component and the second component.
  • an interfacial region may include calcium and/or magnesium diffusing into the other component, or a region containing a mixture of calcium carbonate and magnesium carbonate.
  • An interfacial region may occur, for example, upon thermal treatment (e.g., sintering) of the hybrid structure.
  • a structure described as “amorphous” herein refers to no short or long chain order and a crystalline structure refers to at least some level of order. Materials that may be described as semi-crystalline may therefore be considered crystalline in the present disclosure.
  • the products herein are typically not 100% crystalline or 100% amorphous or non-crystalline, but rather exist on a spectrum between these points.
  • the PCC may be predominantly amorphous or a combination of an amorphous phase and a crystalline phase (such as calcite, vaterite, or aragonite).
  • “Produced directly” refers to a process where a product polymorph (e.g. calcite) is formed without the formation of an intermediate polymorph (e.g. vaterite) that is isolated, and in a second independent step, converted into the product polymorph using a processing technique mentioned herein (e.g. wet aging).
  • a processing technique mentioned herein e.g. wet aging
  • “produced directly” refers to a process whereby the product is formed in one reaction operation.
  • An example of a reaction product that is not “produced directly” may include forming an intermediate polymorph using a reaction method referred to herein, and subsequently isolating the intermediate polymorph, and subjecting it to a processing condition that converts the intermediate polymorph into a different product polymorph.
  • the gypsum used in the present process may be purified gypsum or unpurified gypsum.
  • the gypsum is filtered, sieved, or centrifuged to remove impurities prior to the reacting.
  • the present disclosure relates to a process for converting gypsum into precipitated calcium carbonate, involving reacting a mixture comprising gypsum and a seed, a mineral acid, or both with at least one carbonate source to produce precipitated calcium carbonate.
  • the reactants and the seed and/or the mineral acid control the crystalline polymorph and/or particle size of the precipitated calcium carbonate, the precipitated calcium carbonate is in the form of calcite, and the calcite is produced directly from the reactants without conversion from a vaterite polymorph.
  • a calcite polymorph is produced directly when the mineral acid is citric acid, nitric acid, or phosphoric acid.
  • the mineral acid is an acid with a pKa less than or equal to 3.
  • the gypsum starting material may include carbonate impurities, and, in this scenario, the mineral acid is added with a molar equivalence that is greater than or equal to the molar equivalence of the carbonate impurities in the gypsum.
  • the mineral acid may be present in an amount ranging from 0.1 wt % to 20 wt %, or 0.5 wt % to 10 wt %, or 1 wt % to 5 wt % based on the dry weight of gypsum.
  • a calcite PCC product may be formed when the gypsum is treated with a mineral acid as described in reference to method A and seeded with a calcite seed.
  • less than 25% by weight of a calcium carbonate seed is added to the gypsum, for example less than 10%, less than 5%, or less than 1% by weight based on the gypsum.
  • the seed may be present in an amount ranging from 0.1% to 25%, or 0.5 to 15%, or 1% to 10% by weight based on the gypsum.
  • the PCC produced has a dominant crystal polymorph consistent with calcite, with a geometry comprising rhombic.
  • the PCC produced has a PSD (d 50 ) ranging from 1-28 microns.
  • the PCC has a steepness (d 30 /d 70 ⁇ 100) in a range from 30-100, or 53-71, or 59-63.
  • the PCC has a surface area (BET and/or stearic acid uptake) ranging from 1-30, or from 3-9 m 2 /g.
  • the PCC may have a relatively steep particle size distribution, for example, a steepness greater than about 46.
  • the PCC may have a relatively broad particle size distribution, for example, a steepness less than about 40.
  • a calcite polymorph PCC is produced when the seed is a calcite seed.
  • at least 25% by weight of calcium carbonate is added to the gypsum, at least 10%, at least 5%, at least 2%, or at least 1% by weight based on the gypsum.
  • the seed may be present in an amount ranging from 1% to 25%, or 2 to 30%, or 5% to 40% by weight based on the gypsum.
  • the PCC produced has a dominant crystal polymorph consistent with calcite, with a geometry comprising rhombic.
  • the PCC has a surface area ranging from 0.1-8, or from 2.5-30 m 2 /g.
  • the seed may also be at least one selected from the group consisting of dolomite, dolomitic carbonate, magnesium sulfate, magnesium hydroxide, titania, silica, and zinc oxide.
  • the seed may be dolomitic calcium carbonate.
  • the PCC produced may have a crystal geometry including needle forms of rhombic calcite, as well as other forms. Further, the PCC may have a hybrid structure when seeded with a non-PCC seed material, such as, for example, titania, silica, zinc oxide, or mixtures thereof.
  • the gypsum may be seeded with magnesium sulfate and/or magnesium hydroxide instead of calcium carbonate.
  • the additive may be, but is not limited to a buffer, a dispersant, a thickener, an anticaking agent, a defoamer, a rheology agent, a wetting agent, a crystal seed, a co-solvent, a brightness enhancer, or any agent that affects crystal morphology/geometry of the product.
  • additives include, but are not limited to, citric acid, phosphoric acid, a sugar, BaCl 2 , MgO, MgCO 3 , H 2 SO 4 , H 3 PO 4 , HCl, various phosphates, sodium hexametaphosphate, ammonium sulfate, sodium thiosulfate, and NO 3 compounds.
  • brightness enhancers include, but are not limited to, fluorescent brightening agents.
  • the additive when the additive is an acid, such as, for example, citric acid, the surface area of a resulting PCC morphology may be increased.
  • the selection of the acid, such as, for example, phosphoric acid may be used in varying amounts to control the shape, particle size, and/or surface area of the PCC.
  • a calcite polymorph is produced when the mixture further comprises citric acid, phosphoric acid, ammonium sulfate, or sodium thiosulfate.
  • the weight % of the additive ranges from 0.1% to 20%, or 0.5% to 10%, or 1% to 6% relative to the gypsum.
  • ammonium sulfate is added to the reaction mixture to control the reaction rate.
  • sodium thiosulfate is added instead of ammonium sulfate.
  • the ammonium sulfate may be added to a gypsum slurry. The concentration of ammonium sulfate may be varied to control the PCC polymorph type and particle size.
  • the carbonate source may be at least one selected from the group consisting of ammonium carbonate, ammonium bicarbonate, ammonium carbamate, calcium carbonate, dolomite, a metal carbonate, and carbon dioxide.
  • ammonium carbonate When a mixture of ammonium carbonate is in solution with gypsum, and the reaction takes place in solution, the PCC product tends to be calcite.
  • the carbonate source is a carbonate mixture of ammonium carbonate, ammonium carbamate, and ammonium bicarbonate, and the amount of ammonium bicarbonate is greater than or equal to the amount of ammonium carbamate or ammonium carbonate in the carbonate mixture.
  • ammonium bicarbonate is added to the ammonium carbonate (or vice versa) to generate a mixture, and the mixture is then added to the gypsum.
  • CO 2 gas is bubbled into a slurry containing ammonium hydroxide, and the bubbling results in the formation of ammonium carbonate, and ammonium bicarbonate and/or ammonium carbamate in situ, and the resulting mixture of ammonium carbonate, ammonium carbamate and ammonium bicarbonate is then added to the gypsum.
  • reaction temperature may be equal to or greater than 30° C. and the polymorph formed is calcite.
  • the gypsum is a natural gypsum and the polymorph formed is a calcite and/or vaterite product.
  • the calcium carbonate product may comprise at least 30% by weight calcite relative to the total weight of the product composition and vaterite, at least 40% by weight calcite and vaterite, at least 60% by weight calcite and vaterite, at least 80% by weight calcite and vaterite, or at least 90% by weight calcite and vaterite.
  • the reaction is carried out at a pH equal to or greater than 10 and the polymorph formed is calcite.
  • the carbonate source is carbon dioxide and the carbon dioxide is reacted with ammonia or ammonium hydroxide prior to or during reacting with the mixture comprising gypsum and a seed, a mineral acid, or both.
  • the pH of the mixture is tailored to a pH equal to or greater than 10, which may result in the formation of a calcite polymorph.
  • the pH can be adjusted by adjusting the concentration of the carbon dioxide or the ammonia.
  • the amount of carbonate source added may be greater than the amount of gypsum present in the mixture, where the molar ratio of the gypsum to the carbonate source ranges from about 1:1.1 to 1:5, 1:1.3 to 1:2.5, or from about 1:1.5 to 1:2.
  • the carbon dioxide can be pure carbon dioxide gas, flue gas containing 15-90% carbon dioxide gas, or flue gas with enriched carbon dioxide gas (e.g., greater than 90% CO 2 ).
  • the FGD gypsum is mixed with ammonia prior to the addition of CO 2 .
  • Ammonium hydroxide may be pre-formed by addition of ammonia to water, and the ammonium hydroxide may be fed into slurried gypsum prior to addition of CO 2 .
  • ammonium carbonate may be fully generated, then introduced to the slurried gypsum for reaction. Reacting ammonium hydroxide with CO 2 at room temp to 40° C.
  • ammonium carbonate and ammonium bicarbonate which may react as anticipated with seeded gypsum to produce calcite.
  • ammonium hydroxide with CO 2 yields a mixture of ammonium carbonate and ammonium bicarbonate, which begins to react with gypsum and yield ammonium sulfate during ammonium bicarbonate and ammonium carbonate generation.
  • ammonia and CO 2 are first mixed and reacted, and then the reacted mixture is mixed with the FGD gypsum.
  • the CO 2 is added by bubbling into solution.
  • CO 2 is added as dry ice.
  • the nucleation rate and crystal size of calcium carbonate can be controlled through controlling of the reaction time and temperature.
  • the carbon dioxide, or carbon dioxide equivalent is equimolar or greater to the gypsum reactant.
  • the reaction time may be 0.2-10 hours, or 0.5-3 hours, and the temperature may be in a range from 8-90° C., or from 10-98° C.
  • a CO 2 -containing gas such as a flue gas, may be continuously added during the reaction period with the ammonia.
  • the addition of a CO 2 -containing gas may be stopped during the reaction period with the ammonia. When the CO 2 addition is stopped, it may be optionally restarted prior to a filtration step.
  • the reaction products may be stored before separating the carbonate from ammonium sulfate to allow for ripening of the reaction products.
  • the ripening could be performed with or without the addition of CO 2 during the storage.
  • the CO 2 may be added after the conversion to calcium carbonate and ammonium sulfate.
  • the CO 2 may be added after isolating the calcium carbonate.
  • the introduction of CO 2 such as, for example, after isolating the calcium carbonate or after a reslurrying step, may be used to control the particle size of the calcium carbonate.
  • the carbonate source is an alkali metal carbonate, which is sodium, potassium, cesium, lithium, rubidium, francium.
  • the metal of the metal carbonate is a monovalent ion (e.g., an alkali metal).
  • the PCC produced may have a crystal geometry including needle forms of aragonite, rhombic calcite, and other forms.
  • the metal of the metal carbonate is a divalent ion, such as, for example, magnesium, strontium, beryllium, barium, or radium. Magnesium carbonate may also be yielded under conditions where magnesium cation is present in the gypsum or in the metal carbonate (e.g. magnesium carbonate, dolomite, etc.).
  • the process for converting gypsum into precipitated calcium carbonate further includes processing the precipitated calcium carbonate by at least one method selected from the group consisting of dewatering, drying, ageing, surface treating, size reducing, and beneficiating.
  • Processing PCC with a calcite polymorph may change the aforementioned properties of the calcite. However, the processing does not convert calcite into another polymorph.
  • the present disclosure relates to a process for converting gypsum into precipitated calcium carbonate, involving reacting a mixture comprising gypsum and a seed, a mineral acid, or both with at least one carbonate source to produce precipitated calcium carbonate.
  • the reactants and the seed and/or the mineral acid control the crystalline polymorph and/or particle size of the precipitated calcium carbonate, the precipitated calcium carbonate is in the form of aragonite, and the aragonite is produced directly from the reaction without conversion from a vaterite polymorph.
  • an aragonite polymorph PCC is produced when the seed is aragonite or a blended seed.
  • the blended seed may comprise magnesium carbonate and calcium carbonate, for instance, blended at a ratio of 5:1 or 3:1.
  • at least 10% by weight of seed is added to the gypsum, at least 5%, at least 2%, or at least 1% by weight based on the gypsum.
  • the seed may be present in an amount ranging from 1% to 25%, or 2 to 30%, or 5% to 40% by weight based on the gypsum.
  • the PCC produced has a dominant crystal polymorph consistent with aragonite.
  • the PCC has a surface area (BET and/or stearic acid uptake) ranging from 2 to 30 m 2 /g, or from 5 to 15 m 2 /g, or from 2 to 8 m 2 /g.
  • the seed may also be at least one selected from the group consisting of dolomitic carbonate, magnesium sulfate, magnesium hydroxide, titania, silica, strontium and zinc oxide.
  • the seed may be dolomitic calcium carbonate of high magnesium content.
  • the PCC may have a hybrid structure when seeded with a non-PCC seed material, such as, for example, titania, silica, zinc oxide, strontium or mixtures thereof.
  • the gypsum may be seeded with magnesium sulfate and/or magnesium hydroxide instead of a carbonate.
  • the additive may be, but is not limited to a buffer, a dispersant, a thickener, an anticaking agent, a defoamer, a rheology agent, a wetting agent, a crystal seed, a co-solvent, a brightness enhancer, or any agent that affects crystal morphology/geometry of the product.
  • additives include, but are not limited to, citric acid, phosphoric acid, a sugar, BaCl 2 , MgO, MgCO 3 , H 2 SO 4 , H 3 PO 4 HCl, various phosphates, sodium hexametaphosphate, ammonium sulfate, sodium thiosulfate, and NO 3 compounds.
  • brightness dampeners include, but are not limited to, Fe 2 O 3 , MnO, and Pb +2 .
  • the additive when the additive is an acid, such as, for example, citric acid, the surface area of a resulting PCC morphology may be increased.
  • the selection of the acid, such as, for example, phosphoric acid, may be used in varying amounts to control the shape, particle size, and/or surface area of the PCC.
  • the weight % of the additive ranges from 0.1% to 25%, or 0.5 to 15%, or 1% to 10% relative to the gypsum.
  • ammonium sulfate is added to the reaction mixture to control the reaction rate.
  • sodium thiosulfate is added instead of ammonium sulfate.
  • the ammonium sulfate may be added to a gypsum slurry.
  • the concentration of ammonium sulfate may be varied to control the PCC polymorph type and particle size.
  • the carbonate source may be at least one selected from the group consisting of ammonium carbonate, ammonium bicarbonate, ammonium carbamate, calcium carbonate, dolomite, a metal carbonate, and carbon dioxide.
  • ammonium bicarbonate is added to the ammonium carbonate (or vice versa) to generate a mixture, and the mixture is then added to the gypsum. In another embodiment.
  • CO 2 gas is bubbled into a slurry containing ammonium hydroxide, and the bubbling results in the formation of ammonium carbonate, and/or ammonium bicarbonate and/or ammonium carbamate in situ, and the resulting mixture of ammonium carbonate, ammonium carbamate and ammonium bicarbonate is then added to the gypsum.
  • the carbonate source is carbon dioxide and the carbon dioxide is reacted with ammonia or ammonium hydroxide prior to or during reacting with the mixture comprising gypsum and a seed, a mineral acid, or both.
  • the pH can be adjusted by adjusting the concentration of the carbon dioxide or the ammonia.
  • the amount of carbonate source added may be greater than the amount of gypsum present in the mixture, where the molar ratio of the gypsum to the carbonate source ranges from about 1:1.1 to 1:5, 1:1.3 to 1:2.5, or from about 1:1.5 to 1:2.
  • the carbon dioxide can be pure carbon dioxide gas, flue gas containing 15-90% carbon dioxide gas, or flue gas with enriched carbon dioxide gas (e.g., greater than 90% CO 2 ).
  • the FGD gypsum is mixed with ammonia prior to the addition of CO 2 .
  • Ammonium hydroxide may be pre-formed by addition of ammonia to water, and the ammonium hydroxide may be fed into slurried gypsum (or vice versa) prior to addition of CO 2 .
  • ammonium carbonate or ammonium carbonate with ammonium bicarbonate may be fully generated, then introduced to the slurried gypsum for reaction.
  • ammonium hydroxide with CO 2 yields ammonium bicarbonate and ammonium carbonate, which begins to react with gypsum and yield ammonium sulfate during ammonium bicarbonate and ammonium carbonate generation.
  • ammonia and CO 2 are first mixed and reacted, and then the reacted mixture is added to the FGD gypsum.
  • the CO 2 is added by bubbling into solution.
  • CO 2 is added as dry ice.
  • the nucleation rate and crystal size of calcium carbonate can be controlled through control of the reaction time and temperature.
  • the carbon dioxide, or carbon dioxide equivalent is equimolar or greater to the gypsum reactant.
  • the reaction time may be 0.2-10 hours, or 0.5-3 hours, and the temperature may be in a range from 8-90° C., or from 10-98° C.
  • a CO 2 -containing gas such as a flue gas
  • the addition of a CO 2 -containing gas may be stopped during the reaction period with the ammonia. When the CO 2 addition is stopped, it may be optionally restarted prior to a filtration step.
  • the reaction products may be stored before separating the carbonate from ammonium sulfate to allow for ripening of the reaction products.
  • the ripening could be performed with or without the addition of CO 2 during the storage.
  • the CO 2 may be added after the conversion to calcium carbonate and ammonium sulfate.
  • the CO 2 may be added after isolating the calcium carbonate.
  • the introduction of CO 2 such as, for example, after isolating the calcium carbonate or after a reslurrying step, may be used to control the particle size of the calcium carbonate.
  • the carbonate source is an alkali metal carbonate, which is sodium, potassium, cesium, lithium, rubidium, francium.
  • the metal of the metal carbonate is a monovalent ion (e.g., an alkali metal).
  • the PCC produced may have a crystal geometry including needle forms of aragonite, and other forms.
  • the metal of the metal carbonate is a divalent ion, such as magnesium. Magnesium carbonate may also be yielded under conditions where magnesium cation is present in the gypsum or in the metal carbonate (e.g. magnesium carbonate, dolomite, etc.).
  • the process for converting gypsum into precipitated calcium carbonate further includes processing the precipitated calcium carbonate by at least one method selected from the group consisting of dewatering, drying, ageing, surface treating, size reducing, and beneficiating.
  • the present disclosure relates to a process for converting gypsum into precipitated calcium carbonate, including providing i) gypsum and ii) a seed, or at least one process condition selected from the group consisting of a reaction temperature between 10 and 60° C., or between 18 to 45° C., or between 25 to 35° C.; and reacting the gypsum with at least one carbonate source to produce precipitated calcium carbonate in the form of vaterite.
  • the reactants and the seed and/or process conditions control the particle size of the vaterite.
  • the PCC produced has a dominant crystal polymorph consistent with vaterite, with a geometry comprising spherical “coral” as well as some rhombic.
  • the vaterite PCC may have a flower-shaped geometry, a rose-shaped geometry, a needle-shaped geometry, a ball-shaped or spherical-shaped geometry, or a hexagonal geometry.
  • the geometry or structure of the vaterite may be varied by varying one or more of the reaction rate, pH, reaction temperature, or purity of the feed gypsum.
  • a feed of high-purity gypsum yields vaterite with a ball-shaped geometry, whereas co-generating an ammonia-based carbonate precursor and the PCC tends to yield a more flower-shaped vaterite.
  • ball-shaped vaterite PCC is produced with pre-formed ammonia-based carbonates and lower purity gypsum during the PCC reaction.
  • the PCC produced has a PSD (d 50 ) ranging from 0.1-30, or from 1.0-20, or from 2.0-12.0, or from 3.0-7.0 microns.
  • the PCC has a steepness (d 30 /d 70 ⁇ 100) ranging from 30-100, or 50-100, or 56-83, or 59-71.
  • the PCC has a surface area (BET and/or stearic acid uptake) ranging from 5-75 m 2 /g, or from 5-20 m 2 /g, or from 7-15 m 2 /g.
  • a reaction temperature of less than 30° C. results in a vaterite polymorph.
  • the additive may be, but is not limited to a buffer, a dispersant, a thickener, an anticaking agent, a defoamer, a rheology agent, a wetting agent, a crystal seed, a co-solvent, a brightness enhancer or dampener, or any agent that affects crystal morphology/geometry of the product.
  • additives include, but are not limited to, citric acid, phosphoric acid, a sugar, BaCl 2 , MgO, MgCO 3 , H 2 SO 4 , H 3 PO 4 HCl, various phosphates, sodium hexametaphosphate, ammonium sulfate, sodium thiosulfate, and NO 3 compounds.
  • brightness dampeners include, but are not limited to, Fe 2 O 3 , MnO, and Pb +2 and other lead compounds.
  • the additive is an acid, such as, for example, citric acid
  • the surface area of a resulting PCC morphology may be increased.
  • the selection of the acid, such as, for example, phosphoric acid may be used in varying amounts to control the shape, particle size, and/or surface area of the PCC.
  • the additive is ammonium sulfate, and ammonium sulfate is present in the mixture from 0.5 wt/vol % to 50 wt/vol %, or 2 wt/vol % to 35 wt/vol %, or 4% to 20% by weight.
  • ammonium sulfate is added to the reaction mixture to control the reaction rate.
  • sodium thiosulfate is added instead of ammonium sulfate.
  • the ammonium sulfate may be added to a gypsum slurry. The concentration of ammonium sulfate may be varied to control the PCC polymorph type and particle size.
  • the organic acid is citric acid, and the wt % of citric acid in the mixture is greater than or equal to 0.1%, greater than or equal to 10%, or greater than or equal to 25% relative to the weight of gypsum.
  • the carbonate source is at least one selected from the group consisting of ammonium carbonate, ammonium bicarbonate, ammonium carbamate, calcium carbonate, dolomite, a metal carbonate, and carbon dioxide.
  • the carbonate source is a carbonate mixture of ammonium carbonate, ammonium carbamate, and ammonium bicarbonate, and the amount of ammonium bicarbonate is less than the amount of ammonium carbamate or ammonium carbonate in the carbonate mixture.
  • the PCC yielded is vaterite.
  • ammonium bicarbonate is added to the ammonium carbonate (or vice versa) to generate a mixture, and the mixture is then added to the gypsum.
  • CO 2 gas is bubbled into a slurry containing ammonium hydroxide, and the bubbling results in the formation of ammonium carbonate and/or ammonium carbamate, and ammonium bicarbonate in situ, and the resulting mixture of ammonium carbonate, ammonium carbamate and ammonium bicarbonate is then added to the gypsum.
  • the carbonate source is carbon dioxide and the carbon dioxide is reacted with ammonia or ammonium hydroxide prior to or during reacting with the mixture comprising gypsum and a seed, a mineral acid, or both.
  • the pH of the mixture is tailored to a pH of less than 10, which results in formation of a vaterite polymorph.
  • the carbon dioxide can be pure carbon dioxide gas, flue gas containing 15-90% carbon dioxide gas, or flue gas with enriched carbon dioxide gas (e.g., greater than 90% CO 2 ).
  • the FGD gypsum is mixed with ammonia prior to the addition of CO 2 .
  • Ammonium hydroxide may be pre-formed by addition of ammonia to water, and the ammonium hydroxide may be fed into slurried gypsum prior to addition of CO 2 .
  • ammonia and CO 2 are first mixed and reacted, and then the reacted mixture is added to the FGD gypsum.
  • Reacting ammonium hydroxide with CO 2 at room temp or up to at least 40° C. gives a mixture of ammonium carbonate and ammonium bicarbonate, which reacts as anticipated with unseeded gypsum to give vaterite.
  • ammonium carbonate may be fully generated, then introduced to the slurried gypsum for reaction.
  • ammonium hydroxide with CO 2 yields ammonium carbonate and ammonium bicarbonate, which begins to react with gypsum and yield ammonium sulfate during ammonium bicarbonate and ammonium carbonate generation.
  • the CO 2 is added by bubbling into solution.
  • CO 2 is added as dry ice.
  • the nucleation rate and crystal size of calcium carbonate can be controlled through controlling of the reaction time and temperature.
  • the carbon dioxide, or carbon dioxide equivalent is equimolar or greater to the gypsum reactant.
  • the reaction time is 0.2-10 hours, or 0.5-3 hours, and the temperature is in a range from 8-90° C., or from 10-98° C.
  • a CO 2 -containing gas such as a flue gas
  • the addition of a CO 2 -containing gas may be stopped during the reaction period with the ammonia. When the CO 2 addition is stopped, it may be optionally restarted prior to a filtration step.
  • the reaction products may be stored before separating the carbonate from ammonium sulfate to allow for ripening of the reaction products. The ripening could be performed with or without the addition of CO 2 during the storage.
  • the CO 2 may be added after the conversion to calcium carbonate and ammonium sulfate. According to some embodiments, the CO 2 may be added after isolating the calcium carbonate. According to some embodiments, the introduction of CO 2 , such as, for example, after isolating the calcium carbonate or after a reslurrying step, may be used to control the particle size of the calcium carbonate.
  • the carbonate source is an alkali metal carbonate, such as sodium carbonate, potassium, cesium, lithium, rubidium, or francium based carbonate.
  • the metal of the metal carbonate is a monovalent ion (e.g., an alkali metal).
  • the PCC produced may have a crystal geometry including, for example, spherical vaterite.
  • the metal of the metal carbonate is a divalent ion, such as magnesium, strontium, beryllium, barium, or radium. Magnesium carbonate may also be yielded under conditions where magnesium cation is present in the gypsum or in the metal carbonate (e.g. magnesium carbonate, dolomite, etc.).
  • the process for converting gypsum into precipitated calcium carbonate further includes processing the vaterite by at least one method selected from the group consisting of dewatering, drying, ageing, surface treating, size reducing, and beneficiating, wherein the processing converts the vaterite into a calcite or aragonite polymorph.
  • processing converts the vaterite into a calcite or aragonite polymorph.
  • seeding a vaterite PCC with ground calcium carbonate (GCC) in water with a pH ranging from 4 to 9, or 5 to 8, or 6 to 7.7 converts the vaterite into a calcite polymorph.
  • GCC ground calcium carbonate
  • a GCC seed is provided in 0.1 wt % to 25 wt %, or 0.5 wt % to 15 wt %, or 1 wt % to 10 wt % relative to the vaterite, and the temperature is maintained at less than 35° C.
  • vaterite can be converted to a calcite polymorph by adding ammonium hydroxide or other bases, such as sodium hydroxide, potassium hydroxide or calcium hydroxide to a mixture of vaterite and water, and adjusting the pH to be greater than or equal to 10, or greater than or equal to 10.5, or greater than or equal to 11.
  • the temperature is maintained at a temperature in a range between about 23° C.
  • the conversion process temperature may be maintained for a time period in a range from about 30 minutes to about 12 hours.
  • substantially all of the vaterite may be converted into calcite.
  • the addition of 2 to 10%, 4 to 9%, or 6 to 8% of ammonium bicarbonate to vaterite PCC also aids in conversion to a calcite polymorph.
  • the vaterite and water mixture may be in the form of a wet cake or a slurry.
  • drying of the vaterite stabilizes the vaterite polymorph and prevents it from converting to calcite.
  • the vaterite may be stabilized by the presence of ammonium sulfate, and/or the presence of iron materials, or the absence of ammonium bicarbonate and ammonium sulfate.
  • the vaterite may be stabilized by the presence of ammonium sulfate even when ammonium bicarbonate is present such that the ammonium bicarbonate to ammonium sulfate ratio is between [0:100] and [1:15].
  • the vaterite may be stabilized for 1 day, or 1 week, or a month or longer.
  • the present disclosure relates to a process for converting gypsum into precipitated calcium carbonate involving providing a gypsum, and reacting the gypsum with at least one carbonate source to produce precipitated calcium carbonate in the form of vaterite, such that i) the pH of the wet vaterite is less than or equal to 8, ii) the vaterite is dried.
  • the crystalline content of a PCC composition may be readily determined through visual inspection by use of, for example, a scanning electron microscope or by x-ray diffraction. Such determination may be based upon the identification of the crystalline form and is well known to those of skill in the art.
  • the PCC compositions of the present disclosure are characterized by a single crystal polymorph content of greater than or equal to 30% by weight relative to the total weight of the composition, greater than or equal to 40% by weight, greater than or equal to 60% by weight, greater than or equal to about 80% by weight, or greater than or equal to about 90% by weight.
  • the single crystal polymorph is selected from vaterite, calcite and aragonite.
  • Any of the PCC compositions of the present disclosure in addition to the single crystal vaterite polymorph of greater than or equal to 30% may further or additionally comprise at least one polymorph selected from the group consisting of calcite, aragonite and amorphous calcium carbonate.
  • the present disclosure provides a stable PCC composition or product.
  • stable refers to a polymorph composition having less than a 1% conversion of any of its polymorphs (i.e. vaterite, calcite, aragonite, and amorphous calcium carbonate) over a period of at least 24 hours, or at least 48 hours or at least 72 hours or one week or one month, or less than 0.75%, or less than 0.5%, or less than 0.25%, or less than 0.2%, or less than 0.1% conversion of any of its polymorphs.
  • polymorphs i.e. vaterite, calcite, aragonite, and amorphous calcium carbonate
  • a stable PCC composition product with a 95% vaterite polymorph by weight relative to the total weight of the PCC composition will maintain 94-96% by weight vaterite, or 94.5-95.5% by weight vaterite within a period of at least 24 hours.
  • the stability may vary according to the morphology of the PCC.
  • the PCC compositions may also be characterized by their particle size distribution (PSD).
  • PSD particle size distribution
  • the median particle size also called d 50
  • d 50 is defined as the size at which 50 percent of the particle weight is accounted for by particles having a diameter less than or equal to the specified value.
  • the PCC compositions may have a d 50 in a range from about 0.1 micron to about 30 microns, for example, from about 1 micron to about 28 microns, from about 2 microns to about 14 microns, from about 2 to about 8 microns, from about 1 micron to about 4 microns, or from about 0.1 micron to about 1.5 microns.
  • the d 50 may vary with the morphology of the PCC.
  • calcite PCC may have a d 50 in a range from about 1 to about 28 microns, such as, for example, from about 1 to about 2 microns, from about 1 to about 5 microns, from about 2 to about 4 microns, or from about 4 to about 6 microns.
  • Vaterite PCC may have a d 50 in a range from about 0.1 microns to about 30 microns, such as, for example, from about 0.1 to about 2 microns, from about 1 to about 20 microns, from about 1 to about 10 microns, or from about 2 to about 8 microns.
  • Aragonite PCC may have a d 50 in a range from about 0.1 microns to about 10 microns, such as, for example from about 1 micron to about 8 microns, from about 1.5 to about 6 microns, or from about 2 to about 4 microns.
  • between about 0.1 percent and about 60 percent of the PCC particles are less than about 2 microns in diameter. In other embodiments, between about 55 percent and about 99 percent of the PCC particles are less than 2 microns in diameter. According to some embodiments, less than about 1 percent of the PCC particles are greater than 10 microns in diameter, such as, for example, less than 0.5 percent of the PCC particles are greater than 10 microns in diameter, or less than 0.1% of the PCC particles are greater than 10 microns in diameter.
  • the PCC compositions may be further characterized by their aspect ratio.
  • aspect ratio refers to a shape factor and is equal to the largest dimension (e.g. length) of a particle divided by the smallest dimension of the particle orthogonal to it (e.g. width).
  • the aspect ratio of the particles of a PCC composition may be determined by various methods. One such method involves first depositing a PCC slurry on a standard SEM stage and coating the slurry with platinum. Images are then obtained and the particle dimensions are determined, using a computer based analysis in which it is assumed that the thickness and width of the particles are equal. The aspect ratio may then be determined by averaging fifty calculations of individual particle length-to-width aspect ratios.
  • the PCC compositions may have an aspect ratio in a range from about 1-20, for example, from about 1-15, from about 2-10, or from about 3-5.
  • the aspect ratio may vary with the morphology of the PCC.
  • calcite PCC may have an aspect ratio in a range from about 1-20, such as, for example, from about 1-10, from about 3-5, or from about 1-2.
  • Vaterite PCC may have an aspect ratio in a range from about 1-20, or from about 1-10, such as, for example, from about 1-8, from about 2-5, or from about 1-3.
  • Aragonite PCC may have an aspect ratio in a range from about 1-20, such as, for example, from about 1-15, from about 2-10, or from about 2-5.
  • the PCC compositions may also be characterized in terms of their cubicity, or the ratio of surface area to particle size (i.e., how close the material is to a cube, rectangular prism, or rhombohedron).
  • a lower surface area is advantageous. Smaller particles typically have much higher surface area, but small particle size is advantageous for many different applications. Thus PCC products with small particle size material and lower than “normal” surface area are particularly advantageous. Rhombic crystal forms are generally preferred in terms of cubicity.
  • the PCC compositions may have a cubicity in a range from about 0.03-30, or from about 0.03 to 50, for example, from about 0.04 to 45, from about 0.5-20, from about 1-15, from about 2-10, or from about 3-5.
  • the cubicity may vary with the morphology of the PCC.
  • calcite PCC compositions may have a cubicity in a range from about 0.03 to 50, for example, from about 0.04 to 25, from about 0.5-20, from about 1-15, from about 2-10, or from about 3-5.
  • Vaterite PCC compositions may have a cubicity in a range from about 0.03 to 30, or from about 0.03 to 50, for example, from about 0.1 to 30, from about 0.5-25, from about 1-15, from about 2-10, or from about 3-8.
  • Aragonite PCC compositions may have a cubicity in a range from about 0.03 to 50, for example, from about 0.1 to 30, from about 0.5-20, from about 1-15, from about 2-10, or from about 3-8.
  • the cubic nature of the PCC compositions may be determined by the “squareness” of the PCC particles.
  • a squareness measurement generally describes the angles formed by the faces of the PCC particle. Squareness, as used herein, can be determined by calculating the angle between adjacent faces of the PCC, where the faces are substantially planar. Squareness may be measured using SEM images by determining the angle formed by the edges of the planar faces of the PCC particle when viewed from a perspective that is parallel to the faces being measured. FIG. 41 shows an exemplary measurement of squareness.
  • the PCC compositions may have a squareness in a range from about 70 degrees to about 110 degrees, for example, from about 75 degrees to about 105 degrees, from about 80 degrees to about 100 degrees, or from about 85 to about 95 degrees.
  • the squareness may vary with the morphology of the PCC.
  • calcite PCC compositions may have a squareness in a range from about 70 degrees to about 110 degrees, for example, from about 75 degrees to about 105 degrees, from about 80 degrees to about 100 degrees, or from about 85 to about 95 degrees.
  • Vaterite PCC compositions may have a squareness in a range from about 70 degrees to about 110 degrees, or from about 50 degrees to about 95 degrees, for example, from about 50 degrees to about 105 degrees, from about 60 degrees to about 100 degrees, or from about 50 to about 95 degrees.
  • Aragonite compositions may have a squareness in a range from about 1 degrees to about 179 degrees, for example, from about 5 degrees to about 150 degrees, from about 15 degrees to about 100 degrees, or from about 15 to about 45 degrees.
  • the monodispersity of the product refers to the uniformity of crystal size and polymorphs.
  • the steepness (d 30 /d 70 ⁇ 100) refers to the particle size distribution bell curve, and is a monodispersity indicator.
  • d x is the equivalent spherical diameter relative to which x % by weight of the particles are finer.
  • the PCC compositions may have a steepness in a range from about 30 to about 100, such as, for example, in a range from about 33 to about 100, from about 42 to about 76, from about 44 to about 75, from about 46 to about 70, from about 50 to about 66, from about 59 to about 66, or from about 62 to about 65.
  • the PCC compositions may have a steepness in a range from about 20 to about 71, such as, for example, in a range from about 25 to about 50.
  • the steepness may vary according to the morphology of the PCC. For example, calcite may have a different steepness than vaterite.
  • the PCC compositions may have a top-cut (d 90 ) particle size less than about 2 microns to 25 microns, such as, for example, less than about 17 microns, less than about 15 microns, less than about 12 microns, or less than about 10 microns.
  • the PCC compositions may have a top-cut particle size in a range from about 2 microns to about 25 microns, such as, for example, in a range from about 15 microns to about 25 microns, from about 10 microns to about 20 microns, or from about 3 microns to about 15 microns.
  • the top-cut particle size may vary according to the morphology of the PCC. For example, calcite may have a different top-cut particle size than vaterite.
  • the PCC compositions may have a bottom-cut (d 10 ) particle size less than about 4 microns, such as, for example, less than about 2 microns, less than about 1 micron, less than about 0.7 microns, less than about 0.5 microns, less than 0.3 microns, or less than 0.2 microns.
  • the PCC compositions may have a bottom-cut particle size in a range from about 0.1 micron to about 4 microns, such as, for example, in a range from about 0.1 micron to about 1 micron, from about 1 micron to about 4 microns, or from about 0.5 microns to about 1.5 microns.
  • the bottom-cut particle size may vary according to the morphology of the PCC.
  • calcite may have a different bottom-cut particle size than vaterite.
  • vaterite and calcite may have a bottom-cut particle size in a range from about 0.1 micron to about 4 microns and aragonite may have a bottom-cut particle size in a range from about 0.05 micron to about 4 microns.
  • the PCC compositions may additionally be characterized by their BET surface area.
  • BET surface area refers to the Brunauer-Emmett-Teller (BET) explaining the physical adsorption of gas molecules on a solid surface. It refers to multilayer adsorption, and usually adopts non-corrosive gases (i.e. nitrogen, argon, carbon dioxide and the like) as adsorbates to determine the surface area data.
  • non-corrosive gases i.e. nitrogen, argon, carbon dioxide and the like
  • the BET surface area may vary according to the morphology of the PCC.
  • the PCC may have a BET surface area less than 80 m 2 /g, such as, for example, less than 75 m 2 /g, less than 50 m 2 /g, less than 20 m 2 /g, less than 15 m 2 /g, less than 10 m 2 /g, less than 5 m 2 /g, less than 4 m 2 /g, or less than 3 m 2 /g.
  • the calcite PCC composition particles may have a BET surface area in a range from 1 to 30 m 2 /g, such as, for example, from 2 to 20 m 2 /g, from 3 to 10 m 2 /g, from 3 to 5.0 m 2 /g.
  • calcite PCC may have a BET surface area in a range from 1 to 6 m 2 /g, from 1 to 4 m 2 /g, from 3 to 6 m 2 /g, or from 1 to 10 m 2 /g, from 2 to 10 m 2 /g, or from 5 to 10 m 2 /g.
  • calcite PCC may have a BET surface area less than or equal to 30 m 2 /g.
  • Vaterite PCC may have a BET surface area in a range from 5 to 75 m 2 /g, such as, for example, from 10 to 60 m 2 /g, from 20-50 m 2 /g, from 25 to 40 m 2 /g, or from 30 to 35 m 2 /g
  • the vaterite PCC composition particles have a BET surface area in a range from 7 to 18 m 2 /g, from 5 to 20 m 2 /g, or from 7 to 15 m 2 /g.
  • Aragonite PCC may have a BET surface area in the range from 2 to 30 m 2 /g, such as, for example, from 5 to 20 m 2 /g or from 10 to 15 m 2 /g.
  • the PCC compositions may additionally be characterized by the ratio of BET surface area to d 50 .
  • the vaterite PCC composition particles have a ratio of BET surface area to d 50 of 1-6.5, 2-5.5, or 2.5-5.
  • the calcite PCC composition particles have a ratio of BET surface area to d 50 of 0.6-2, 0.7-1.8, or 0.8-1.5.
  • the PCC compositions may additionally be characterized by their stearic acid uptake surface area.
  • stearic acid uptake surface area refers to a surface treatment of the PCC compositions with stearic acid. Under controlled conditions, the stearic acid may form a monolayer on the surface of the PCC and thus provide information regarding the surface area via adsorption or uptake of stearic acid.
  • the stearic acid uptake surface area may vary according to the morphology of the PCC.
  • the PCC may have a stearic acid uptake surface area less than 80 m 2 /g, such as, for example, less than 75 m 2 /g, less than 50 m 2 /g, less than 20 m 2 /g, less than 15 m 2 /g, less than 10 m 2 /g, less than 5 m 2 /g, less than 4 m 2 /g, or less than 3 m 2 /g.
  • the calcite PCC composition particles have a stearic acid uptake surface area in a range from 1 to 30 m 2 /g, such as, for example, from 2 to 20 m 2 /g, from 3 to 10 m 2 /g, from 3 to 5.0 m 2 /g.
  • calcite PCC may have a stearic acid uptake surface area in a range from 1 to 6 m 2 /g, from 1 to 4 m 2 /g, from 3 to 6 m 2 /g, or from 1 to 10 m 2 /g, from 2 to 10 m 2 /g, or from 5 to 10 m 2 /g.
  • calcite PCC may have a stearic acid uptake surface area less than or equal to 30 m 2 /g.
  • Vaterite PCC may have a stearic acid uptake surface area in a range from 5 to 75 m 2 /g, such as, for example, from 10 to 60 m 2 /g, from 20-50 m 2 /g, from 25 to 40 m 2 /g, or from 30 to 35 m 2 /g.
  • the vaterite PCC composition particles have a stearic acid uptake surface area in a range from 7 to 18 m 2 /g, from 5 to 20 m 2 /g, or from 7 to 15 m 2 /g.
  • Aragonite PCC may have a stearic acid uptake surface area in the range from 2 to 30 m 2 /g, such as, for example, from 5 to 20 m 2 /g or from 10 to 15 m 2 /g.
  • the yield of PCC using the process herein is greater than 50%, greater than 60%, greater than 80%, or greater than 90%.
  • the PCC compositions comprise substantially precipitated calcium carbonate (CaCO 3 ).
  • various organic or inorganic materials may be present in the PCC compositions including, but not limited to, iron (Fe), ammonium hydroxide (NH 4 OH), ammonium carbonate (NH 4 ) 2 CO 3 , ammonium sulfate (NH 4 ) 2 SO 4 , calcium sulfate (CaSO 4 ), magnesium carbonate (MgCO 3 ), calcium oxide (CaO) and combinations thereof.
  • the PCC composition comprising vaterite PCC, calcite PCC, aragonite PCC and/or amorphous PCC and/or mixtures thereof comprise at least one of these impurities.
  • the quantity of these impurities present may vary according to morphology of the PCC and/or the methods and techniques used in their formation.
  • the PCC composition has a NH 4 OH content by weight relative to the total weight of the PCC composition of less than 35 wt %, such as, for example, less than 30 wt %, less than 25 wt %, less than 20 wt %, less than 15 wt %, less than 10 wt %, less than 5 wt % or less than 2 wt %.
  • the PCC composition has a NH 4 OH content by weight relative to the total weight of the PCC composition from 0 to 35 wt %, from 1 to 30 wt %, from 2 to 25 wt %, from 3 to 20 wt %, from 4 to 15 wt %, or from 5-10 wt %.
  • the PCC composition has a (NH 4 ) 2 CO 3 content by weight relative to the total weight of the PCC composition of less than 40 wt %, such as, for example, less than 35 wt %, less than 30 wt %, less than 25 wt %, less than 20 wt %, less than 15 wt %, less than 10 wt %, less than 5 wt % or less than 2 wt %.
  • the PCC composition has a (NH 4 ) 2 CO 3 content by weight relative to the total weight of the PCC composition from 0 to 40 wt %, from 1 to 35 wt %, from 2 to 30 wt %, from 3 to 25 wt %, from 4 to 20 wt %, from 5-15 wt %, or from 5-10 wt %.
  • the PCC composition has a (NH 4 ) 2 SO 4 content by weight relative to the total weight of the PCC composition of less than 35 wt %, such as, for example, less than 30 wt %, less than 25 wt %, less than 20 wt %, less than 15 wt %, less than 10 wt %, less than 5 wt % or less than 2 wt %.
  • the PCC composition has a (NH 4 ) 2 SO 4 content by weight relative to the total weight of the PCC composition from 0 to 35 wt %, from 1 to 30 wt %, from 2 to 25 wt %, from 3 to 20 wt %, from 4 to 15 wt %, or from 5 to 10 wt %.
  • the PCC composition has a CaSO 4 content by weight relative to the total weight of the PCC composition of less than 50 wt %, such as, for example, less than 40 wt %, less than 35 wt %, less than 30 wt %, less than 25 wt %, less than 20 wt %, less than 15 wt %, or less than 12 wt %.
  • the PCC composition has a CaSO 4 content by weight relative to the total weight of the PCC composition from 10 to 50 wt %, from 15 to 40 wt %, from 20 to 35 wt %, or from 25 to 30 wt %.
  • the PCC composition has a MgCO 3 content by weight relative to the total weight of the PCC composition of less than 50 wt %, such as, for example, less than 40 wt %, less than 35 wt %, less than 30 wt %, less than 25 wt %, less than 20 wt %, less than 15 wt %, less than 10 wt %, or less than 5 wt %.
  • the PCC composition has a MgCO 3 content by weight relative to the total weight of the PCC composition from 2 to 50 wt %, from 5 to 40 wt %, from 10 to 35 wt %, from 15 to 30 wt % or from 20 to 25 wt %.
  • the PCC composition has a CaO content by weight relative to the total weight of the PCC composition of less than 10 wt %, such as, for example, less than 9 wt %, less than 8 wt %, less than 7 wt %, or less than 6 wt %. In some embodiments, the PCC composition has a CaO content by weight relative to the total weight of the PCC composition from 5 to 10 wt %, from 6 to 9 wt %, from 7 to 8 wt %, or from 7.25 to 7.75 wt %.
  • the PCC composition has a Fe content by weight relative to the total weight of the PCC composition of greater than 0.04 wt %, such as, for example, greater than 0.05 wt %, greater than 0.10 wt %, greater than 0.25 wt %, greater than 0.5 wt %, greater than 0.75 wt %, greataer than 1 wt %, greater than 2 wt %, or greater than 5 wt %.
  • the PCC composition has a Fe content by weight relative to the total weight of the PCC composition from 0.04 to 10 wt %, from 0.05 to 5 wt %, from 0.06 to 1 wt %, from 0.07 to 0.8 wt %, from 0.08 to 0.6 wt %, from 0.1 to 0.5 wt %, or from 0.2 to 0.4 wt %.
  • PCC precipitated calcium carbonate
  • the PCC compositions of the present disclosure provide PCC compositions which emit an amount of carbon dioxide during production (i.e. from gypsum) that is less than an amount of carbon dioxide emitted during the production of a PCC by calcining and slaking natural calcium carbonate.
  • the processes described herein do not involve calcining natural calcium carbonate or slaking/carbonation steps, and thus emit less carbon dioxide leading to a lower carbon footprint. Further, as the processes described herein do not involve calcining/slaking steps, the PCC compositions thus produced may have a higher iron content in the final PCC product. Thus, one aspect of the present disclosure is a low carbon footprint PCC composition. Alternatively, the low carbon footprint PCC compositions may be thought of as “higher” iron PCC compositions.
  • the low carbon footprint PCC compositions of the present disclosure comprise a first iron content which is inversely correlated with the carbon dioxide emissions of the process by which the low carbon footprint PCC composition is produced.
  • a PCC composition produced by calcining and slaking natural calcium carbonate will comprise a second iron content.
  • the first iron content is greater than the second iron content, indicating a PCC composition having a lower carbon footprint.
  • the low carbon footprint PCC composition has a Fe content by weight relative to the total weight of the low carbon footprint PCC composition of greater than 0.04 wt %, such as, for example, greater than 0.05 wt %, greater than 0.10 wt %, greater than 0.25 wt %, greater than 0.5 wt %, greater than 0.75 wt %, greater than 1 wt %, greater than 2 wt %, or greater than 5 wt %.
  • the low carbon footprint PCC composition has a Fe content by weight relative to the total weight of the low carbon footprint PCC composition from 0.04 to 10 wt %, from 0.05 to 5 wt %, from 0.06 to 1 wt %, from 0.07 to 0.8 wt %, from 0.08 to 0.6 wt %, from 0.1 to 0.5 wt %, or from 0.2 to 0.4 wt %.
  • the Fe content by weight may vary according to the morphology of the low carbon footprint PCC and the methods used to produce the low carbon footprint PCC.
  • the PCC compositions of the present disclosure may be in any desired form, including but not limited to, powders, crystalline solids, or in dispersed form, i.e., the PCC compositions may be dispersed in a liquid, such as in an aqueous medium.
  • the dispersed PCC composition comprises at least about 50% PCC by weight relative to the total weight of the dispersion, at least about 70% PCC by weight.
  • the dispersed PCC composition may comprise at least one dispersing agent, which may be chosen from dispersing agents now known in the art or hereafter discovered for the dispersion of PCC.
  • Suitable dispersing agents include, but are not limited to: polycarboxylate homopolymers, polycarboxylate copolymers comprising at least one monomer chosen from vinyl and olefinic groups substituted with at least one carboxylic acid group, and water soluble salts thereof.
  • suitable monomers include, but are not limited to, acrylic acid, methacrylic acid, itaconic acid, crotonic acid, fumaric acid, maleic acid, maleic anhydride, isocrotonic acid, undecylenic acid, angelic acid, and hydroxyacrylic acid.
  • the at least one dispersing agent may be present in the dispersed PCC composition in an amount ranging from about 0.01% to about 2%, from about 0.02% to about 1.5% by weight relative to the total weight of the dispersion.
  • FGD gypsum typically contains contaminants and is of low whiteness and brightness.
  • Major contributors to discoloration may include insoluble impurities, such as pyrite and various organic species.
  • gypsum may be pretreated prior to reaction with a carbonate source. In one embodiment, this pretreatment includes, but is not limited to, a filtration or sieving step and/or a mineral acid treatment step.
  • the filtration method may be, but is not limited to vacuum filtration.
  • Fully dissolved gypsum may be filtered or centrifuged to remove the impurities that result in low whiteness and brightness.
  • the filtration method may be, but is not limited to vacuum filtration, but may refer to any dewatering process common to the art.
  • large contaminants may be removed from the gypsum by sieving.
  • a mineral acid such as nitric acid, may be employed to improve whiteness and brightness of the gypsum by removing species causing discoloration.
  • a mineral acid may also be employed to remove remaining carbonate species in the gypsum. Therefore, in terms of methods A and B wherein mineral acid is added to remove excess carbonate, additional mineral acid may be added to remove non-carbonate contaminants.
  • the mineral acid addition step of methods A and B to remove carbonate impurities may be different from the mineral acid used to remove contaminants resulting in low whiteness and brightness, and the step to remove carbonate impurities may take place prior to the step to remove contaminants resulting in low whiteness and brightness, and vice versa.
  • the method may be modified to include a step for removing impurities and/or improving the whiteness and brightness of the gypsum by filtering from the fully dissolved gypsum, sieving, and/or utilizing a mineral acid.
  • the PCC compositions may have low ionic impurities.
  • the low ionic impurities may improve the electrical properties of the PCC or a finished product containing the PCC. It is envisioned that this pretreatment step is performed prior to reacting gypsum with the carbonate source, additive, or seed and that a gypsum of improved whiteness and brightness may yield, after reaction with a carbonate source, a PCC product of whiteness and brightness similar to that of the cleaned gypsum. Polymorph and particle size of the PCC yielded may be controlled using methods disclosed herein, in one or more of their embodiments.
  • Brightness refers to a measure of directional reflectance from a material of light at a certain wavelength or certain wavelengths.
  • ISO brightness refers to an ISO standard that quantifies the brightness of a substantially white or near-white material (i.e. paper) as it would be perceived in an environment that is illuminated with a mixture of cool-white fluorescence and some filtered daylight, specifically blue light of specific spectral and geometric characteristics, generally ⁇ 457 nm.
  • the ISO brightness may be determined by a standard test for brightness, such as ASTM D985-97.
  • the PCC compositions or paper or paperboard materials comprising them may have an ISO brightness greater than or equal to 54, such as, for example, greater than or equal to 65, greater than or equal to 85, greater than or equal to 88, greater than or equal to 90, greater than or equal to 92, greater than or equal to 94, or greater than or equal to 95.
  • the PCC compositions have a consistent or homogeneous brightness across the PCC particles.
  • the PCC compositions may have an ISO brightness in the range of about 54 to about 99, such as, for example, in a range from about 54 to about 97, from about 54 to about 96, from about 60 to about 95, from about 75 to about 95, from about 80 to about 95, or from about 85 to about 90.
  • the ISO brightness may vary according to the morphology of the PCC. For example, calcite may have a different ISO brightness than vaterite.
  • DIN yellowness index refers to an DIN standard that quantifies and provides numbers that correlate with visual ratings of yellowness or whiteness of white and near-white or colorless object-color samples.
  • the DIN yellowness index may be determined by a standard test for yellowness, such as ASTM E313-15e1.
  • the PCC compositions or paper or paperboard materials comprising them may have a DIN yellowness index of less than or equal to 10.5, such as, for example, less than or equal to 8, less than or equal to 5, less than or equal to 2, less than or equal to 1, less than or equal to 0.8, less than or equal to 0.75.
  • the PCC compositions have a consistent or homogeneous DIN yellowness index across the PCC particles.
  • the PCC compositions may have a DIN yellowness index in the range of about 0.7 to about 10.3, such as, for example, in a range from about 0.8 to about 8, from about 0.9 to about 6, from about 1.0 to 3, or from about 1.0 to about 1.5.
  • the DIN yellowness index may vary according to the morphology of the PCC. For example, calcite may have a different DIN yellowness index than vaterite.
  • Rhombic precipitated calcium carbonate of a particular size distribution can be yielded from FGD gypsum by reacting with ammonium carbonate in the presence of a calcium carbonate crystal seed and by controlling reaction parameters as disclosed herein.
  • Rhombic PCC generated from this method has similar properties to either rhombic produced by traditional methods or ground calcium carbonate (GCC).
  • Reaction of gypsum with carbonate in the presence or absence of additives to yield the rhombic PCC can be carried out in a batch or continuous process. Specific selection of reaction conditions aid in fine-tuning the properties of the PCC generated. The following may be controlled for rhombic PCC production disclosed herein: concentration of gypsum and other reactants, starting temperature for each reactant, reaction temperature and reaction time, drying temperature, annealing temperature for generated PCC where employed, selection and maintenance of pH and ionic strength for each solution, addition rate of each added component, and rate of CO 2 addition, where employed.
  • PCC may be surface treated with stearic acid, other stearate or hydrocarbon species to yield a specific level of hydrophobicity.
  • Hydrophobicity may be measured using a moisture uptake (MPU) technique, in which a PCC powder is exposed to a high relative humidity atmosphere for 24 h or longer and the weight change due to water sorption is recorded. In general, the maximum reduction in MPU achievable by surface treatment is particularly advantageous.
  • Hydrophobicity may also be measured by contact angle, in which a droplet of a test liquid (e.g. water) is placed on a PCC powder and is observed to see whether the droplet is absorbed (wets) or gives a stable droplet with a measurable contact angle.
  • a test liquid e.g. water
  • Surface treatments may involve dry or wet coating with a C 6 -C 22 fatty acid or fatty acid salt. Such treatments are well-known in the art, and in addition to stearic acid, include such materials as ammonium stearate, sodium stearate, palmitic acid, and others.
  • the fatty acid/fatty acid salt is provided in sufficient quantity to coat a substantial portion of the surface of the majority of PCC particles.
  • the amount of hydrophobizing agent needed to coat a substantial portion of the PCC surface is related to the PCC surface area.
  • a calcite PCC of this disclosure requires 0.5-1.0% hydrophobizing agent to coat the surface.
  • a vaterite PCC requires 2.0-3.0% hydrophobizing agent to coat the surface.
  • Treated and untreated PCC or blends thereof, of single or blended size distributions can be used in a variety of applications, including adhesives and sealants as a rheology modifier, in paints and ink for opacity and as an extender, as a paper filler, for surface finishing and brightness, a functional filler in plastics and as an extender.
  • the hydrophobizing agent may form a monolayer on the surface of the PCC.
  • the amount of hydrophobizing agent may be in a range from about 0.15 m 2 /g to about 18 m 2 /g to coat the particles, such as, for example, in a range from about 0.15 m 2 /g to about 8 m 2 /g or from about 10 m 2 /g to about 17 m 2 /g.
  • the amount of hydrophobizing agent may be dependent on the morphology of the PCC.
  • calcite PCC may have an amount of hydrophobizing agent in a range from about 0.15 m 2 /g to about 20 m 2 /g to coat the particles
  • vaterite PCC may have an amount of hydrophobizing agent in a range from about 10 m 2 /g to about 80 m 2 /g to coat the particles.
  • a size reduction method is employed either in situ or on the product after recovery.
  • a size reduction method may include sonication or grinding. Since the products appear to exhibit ‘substructure’ that is most likely interpretable as aggregation, a size reduction method may break apart the aggregates into their constituent building blocks. According to some embodiments, ultrasound may be used to break down agglomerates.
  • the PCC may be beneficiated by grinding or milling.
  • the beneficiation may include one or more of magnetic separation, bleaching, or acid washing.
  • the separation, bleaching, or acid washing may occur before the grinding/milling, after the grinding/milling, or both.
  • the PCC compositions of the present disclosure may optionally comprise at least one added pigment.
  • Suitable pigments are those now known or that may be hereafter discovered.
  • Exemplary pigments include, but are not limited to, titanium dioxide, calcined clays, delaminated clays, talc, calcium sulfate, other calcium carbonate, kaolin clays, calcined kaolin, satin white, plastic pigments, aluminum hydrate, and mica.
  • the pigment may be present in the PCC compositions of the present disclosure in an amount less than about 70% by weight relative to the total weight of the composition. It is to be understood that the skilled artisan will select any amounts of the optional at least one second PCC form and the optional at least one pigment in such a way so as to obtain various desired properties without affecting, or without substantially affecting, the advantageous properties of the PCC compositions disclosed herein.
  • the present disclosure also relates to a process for converting limestone, marble, or chalk into precipitated calcium carbonate comprising i) treating limestone, marble, or chalk with a mineral acid comprising sulfate anions to yield a calcium sulfate and magnesium sulfate mixture ii) optionally adding a calcium carbonate seed to the calcium sulfate iii) optionally adding an additive to the calcium sulfate iv) reacting the calcium sulfate with at least one carbonate source selected from the group consisting of ammonium carbonate, ammonium bicarbonate, ammonium carbamate, calcium carbonate, dolomite, a metal carbonate, and carbon dioxide at a reaction temperature of 8-50° C. and a reaction time of 5-250 minutes, to yield precipitated calcium carbonate and v) isolating the precipitated calcium carbonate.
  • reaction conditions are used to control the crystalline polymorph and particle size of the precipitated calcium carbonate thus obtained.
  • Limestone is a sedimentary rock composed largely of the minerals calcite and aragonite.
  • Dolomitic quicklime is calcined dolomite that is rehydrated (e.g., MgOH and CaOH).
  • Certain embodiments of the present disclosure relate to a low energy method of producing precipitated calcium carbonate of controlled polymorph and particle size with limestone, marble, or chalk as the calcium source.
  • Treating an impure calcium carbonate source with sulfuric acid generates sulfate products, including calcium sulfate (gypsum) and magnesium sulfate.
  • gypsum calcium sulfate
  • magnesium sulfate magnesium sulfate
  • a PCC and sulfate-based solution-phase byproduct are generated.
  • the polymorph and particle size of PCC generated from gypsum produced in this process can be controlled by methods disclosed within, in one or more of their embodiments.
  • the use of sulfuric acid and limestone to generate gypsum is known in the art.
  • magnesium carbonate can be generated from MgSO 4 formed during dolomitic limestone reaction with sulfuric acid and dissolved in the aqueous phase by reaction with an appropriate carbonate.
  • the amount of sulfuric acid added to limestone is optionally a molar equivalent of or in excess of the amount of calcium present in the limestone.
  • the present disclosure relates to a precipitated calcium carbonate compound with a vaterite polymorph.
  • the vaterite precipitated calcium carbonate described within has novel structural characteristics, such as particle size distribution (PSD), steepness, and BET surface area, as compared to heretofore known vaterite precipitated calcium carbonate. See Table 3 below for vaterite characteristics.
  • the PCC compositions may also be characterized in terms of their cubicity, or the ratio of surface area to particle size (i.e., how close the material is to a perfect cube). According to certain embodiments of the present disclosure, a lower surface area is advantageous. Smaller particles typically have much higher surface area, but small particle size is advantageous for many different applications. Thus PCC products with small particle size material and lower than “normal” surface area are particularly advantageous. Rhombic crystal forms are generally preferred in terms of cubicity.
  • FIG. 14 shows a PCC composition having a relatively low surface area to particle size ratio because of the relatively smooth, planar faces of the particles.
  • FIG. 24 shows a PCC composition having relatively non-planar faces because of protrusions on the faces of the particles, and therefore, the composition shown has a higher surface area and a lower cubicity.
  • FIG. 41 shows an exemplary measurement of squareness.
  • the PCC compositions may have a squareness in a range from about 70 degrees to about 110 degrees.
  • Five measurements of angles between the planar faces of the PCC particles in FIG. 41 were taken using IMAGE J analysis software, one of which is shown in FIG. 41 . Angles were measured by randomly selecting particles from those having faces normal to the plane of the image. The measured angles between the edges were 74.6 degrees, 105.2 degrees, 109.6 degrees, 82.6 degrees, and 74.3 degrees.
  • the squareness of the PCC particles may be in a range from about 70 degrees to about 110 degrees, such as, for example, in a range from about 75 degrees to about 105 degrees, or from about 80 degrees to about 110 degrees.
  • the monodispersity of the product refers to the uniformity of crystal size and polymorphs.
  • the steepness (d 30 /d 70 ⁇ 100), as defined above, refers to the particle size distribution bell curve, and is a monodispersity indicator.
  • the preferred PCC product is monodisperse with a steepness greater than 30, or greater than 40, or greater than 50, and less than 60, or even less than 65.
  • the PCC may have a steepness in a range from about 30 to about 100, such as, for example, in a range from about 34 to about 100, from about 42 to about 77.
  • the steepness may vary according to the morphology of the PCC. For example, calcite may have a different steepness than vaterite.
  • the present disclosure enables the generation of varied PSD (d 50 ) and polymorphs of the PCC product, which can be formed as vaterite, aragonite, calcite (e.g., rhombic or scalenohedral calcite), or amorphous calcium carbonate.
  • calcite e.g., rhombic or scalenohedral calcite
  • amorphous calcium carbonate e.g., calcium carbonate.
  • lower reaction temperature yields smaller/finer, higher surface area vaterite ‘balls’.
  • lower excess of ammonium carbonate yields smaller/finer crystals within aggregates, and higher surface area products often comprised of a calcite/vaterite blend.
  • the PCC composition of the present disclosure is characterized by a single vaterite crystal polymorph content of greater than or equal to 30% by weight relative to the total weight of the composition, greater than or equal to 40% by weight, greater than or equal to 60% by weight, greater than or equal to about 80% by weight, or greater than or equal to about 90% by weight.
  • the vaterite PCC has a geometry comprising spherical coral, elliptical coral, rhombic, flower-shaped or mixtures thereof.
  • the vaterite PCC has a PSD (d 50 ) ranging from 0.1-30, 1-28, 2.0-7.0, 2.4-6.0, or 2.6-5.5 microns.
  • the vaterite PCC has a steepness (d 50 /d 70 ⁇ 100) ranging from 30-100, 37-100, 40-83, 42-71.
  • the vaterite PCC has a BET surface area ranging from 1-75, 5-75, 1-30, 2-30, 8-18, 10-17, or 10.4-16.1 m 2 /g.
  • the vaterite PCC may have an amount of hydrophobizing agent in a range from about 10 m 2 /g to about 17 m 2 /g to coat the particles.
  • the present disclosure also relates to a precipitated calcium carbonate compound with a calcite polymorph.
  • the calcite precipitated calcium carbonate described within has improved structural characteristics, such as particle size distribution (PSD), steepness, and BET surface area, as compared to heretofore known calcite precipitated calcium carbonate. See Table 3 for a comparison of calcite manufactured from the process herein and a known PCC calcite.
  • the PCC composition of the present disclosure is characterized by a single calcite crystal polymorph content of greater than or equal to 30% by weight relative to the total weight of the composition, greater than or equal to 40% by weight, greater than or equal to 60% by weight, greater than or equal to about 80% by weight, or greater than or equal to about 90% by weight.
  • the calcite PCC has a rhombic geometry.
  • seeding gypsum with crystallized calcium carbonate consistently yields rhombic PCC.
  • Seeding with calcite, dolomite, or magnesite yields rhombic PCC.
  • seeding with coarse scalenohedral PCC >5% yields a larger/coarser and a higher surface area product.
  • seeding with fine rhombohedral PCC ⁇ 5% yields a finer crystal size within the aggregate; >5% gives finer aggregates.
  • ammonium carbonate conditions influence rhombic PCC formation.
  • rhombic PCC yielded may be small stacked plates of 300-500 nm, forming inconsistent or consistent particle shapes, having a d 50 of 1-28 ⁇ m or 1-6 ⁇ m, a steepness of 30-100 or 56-91, and a BET surface area of 1-30 m 2 /g or 2-5 m 2 /g.
  • Table 4 identifies product characteristics obtained from various examples of the foregoing methods.
  • the calcite PCC has a PSD (d 50 ) ranging from 1-28, 1.8-6.0, 2.2-5.8, or 2.8-5.6 microns.
  • the calcite PCC has a steepness (d 30 /d 70 ⁇ 100) ranging from 30-100, 40-100, 50-83, 56-71.
  • the calcite PCC has a BET surface area ranging from 2-25, 3.0-7.0, 3.1-6.0, or 3.5-5.0 m 2 /g.
  • the calcite PCC may have an amount of hydrophobizing agent in a range from about 0.15 m 2 /g to about 8 m 2 /g to coat the particles.
  • the present disclosure also relates to a precipitated calcium carbonate compound with an aragonite polymorph.
  • the aragonite precipitated calcium carbonate described within has improved structural characteristics, such as particle size distribution (PSD), steepness, and BET surface area, as compared to heretofore known aragonite precipitated calcium carbonate.
  • the PCC compound of the present disclosure is characterized by a single aragonite crystal polymorph content of greater than or equal to 30% by weight relative to the total weight of the composition, greater than or equal to 40% by weight, greater than or equal to 60% by weight, greater than or equal to about 80% by weight, or greater than or equal to about 90% by weight.
  • the morphology may be changed through post-processing techniques, such as aging.
  • an amorphous PCC may be used as a precursor to convert into a crystalline morphology, such as vaterite, aragonite, or calcite.
  • a metastable PCC such as vaterite or aragonite, may be converted to calcite through aging, such as, for example, wet aging. The amount of vaterite converted to calcite through aging may be varied by adjusting the properties of the aging conditions.
  • the aging may be varied by the presence or absence of ammonium sulfate, including the amount of ammonium sulfate, the aging temperature, and the concentration of wet cake solids.
  • the vaterite when less than about 90% vaterite is present, the vaterite will convert to calcite.
  • the vaterite can be retained in a dry powder or wet cake. The amount of retained vaterite may vary depending on the aging parameters.
  • vaterite can be converted to calcite through a mechanical process, such as by grinding or ball milling the vaterite.
  • the concentrations of gypsum and ammonium carbonate may influence the conversion of vaterite to calcite.
  • higher concentrations of gypsum and ammonium carbonate may produce vaterite PCC that is more stable (e.g., resistant to converting to calcite) than vaterite PCC produced using lower concentrations of gypsum and ammonium carbonate.
  • the reaction forms vaterite that converts to calcite in the presence of ammonium sulfate within 24 hours.
  • the vaterite produced may be more stable.
  • the reaction forms vaterite, but the vaterite is stable in the presence of ammonium sulfate for at least 24 hours.
  • impurities such as, for example, iron present in either gypsum or ammonium-based carbonates may assist stabilizing vaterite PCC produced by the methods described herein.
  • the conversion of vaterite to calcite may be controlled through the storage of the vaterite.
  • vaterite in liquid suspension with ammonium sulfate may convert to calcite may be inhibited relative to cakes of vaterite having about 40-60% solids without ammonium sulfate.
  • the conversion of vaterite to calcite may reduce the surface area of the PCC formed.
  • the conversion of vaterite to calcite may reduce the surface area of the PCC from greater than 10 m 2 /g (vaterite) to less than 1 m 2 /g (calcite).
  • the conversion of vaterite to calcite may increase the particle size of the PCC.
  • the conversion of vaterite to calcite may not significantly change the particle size of the PCC.
  • Other additives such as, for example, citric acid may inhibit the conversion of vaterite to calcite.
  • citric acid may inhibit the conversion of vaterite to calcite.
  • about 5% by weight citric acid on vaterite may inhibit the conversion to calcite.
  • adding ammonium bicarbonate may accelerate the conversion of vaterite to calcite, whereas ammonium sulfate in concentrations from about 0.5% to about 10% by weight may slow or inhibit the conversion to calcite.
  • FIG. 39 shows exemplary effects on morphology of the PCC by varying the feed concentrations and the aging process.
  • FIG. 40 shows exemplary effects of the feed composition on PCC.
  • the methods of forming the PCC compound may be performed in a continuous process, such as, for example, using a tubular reactor.
  • the reactants may be mixed in such a way as to cause cavitation.
  • the present disclosure relates to commercial applications of the vaterite, calcite, and/or aragonite precipitated calcium carbonate compound described herein, in one or more of its embodiments.
  • the present disclosure relates to a polymer film or a breathable polymer film containing the vaterite, calcite, and/or aragonite precipitated calcium carbonate compound in one or more of its embodiments.
  • the present disclosure relates to a pulp or paper material or product containing the vaterite, calcite, and/or aragonite precipitated calcium carbonate compound in one or more of its embodiments.
  • the paper product comprises the precipitated calcium carbonate as a filler or as a coating.
  • the paper material or paper product may be a paper towel, an absorbent cloth or a sanitary napkin.
  • the present disclosure relates to a diaper comprising a breathable polymer film containing the vaterite, calcite, and/or aragonite precipitated calcium carbonate compound in one or more of its embodiments.
  • the present disclosure relates to a filled polymer composition
  • a filled polymer composition comprising the PCC of the present disclosure in one or more of its embodiments as filler, wherein the polymer can be any desired polymer or resin.
  • the polymeric material of the filled polymer composition may be natural or synthetic.
  • the polymeric material of the filled polymer composition may be biodegradable.
  • the PCC compositions may be used as a filler for various applications.
  • Exemplary applications include, but are not limited to, fillers or additives for plastics, paper coatings, adhesives, sealants, caulks, paper, moldings, coatings, paint, rubber products, and concrete.
  • the PCC compositions may be used as a filler or additive for polyvinylchloride (PVC), plasticized PVC (pPVC), polypropylene (PP), rubber, coatings, paint, ceramics, paper, or concrete.
  • PVC polyvinylchloride
  • pPVC plasticized PVC
  • PP polypropylene
  • Some exemplary uses include use as a filler or additive for PVC pipes or moldings, pPVC, paint (e.g., exterior paint or road paint), tile coatings (e.g., ceiling tile coatings), decorative coatings, moldings (e.g., PVC moldings, pPVC moldings, or PP moldings), sheet molding compounds, bulk molding compounds, adhesives, caulks, sealants, rubber products, paper, paper fillers, paper coatings, or concrete.
  • the relatively lower surface area of the PCC compositions may be suitable as a filler and may have improved dispersibility.
  • the PCC compositions may, in general, have relatively low brightness (e.g.
  • the PCC compositions disclosed herein may have a relatively low surface area when compared to other calcium carbonate products, such as, for example, ground calcium carbonate (GCC).
  • GCC ground calcium carbonate
  • the relatively low surface area may contribute to low adsorption of additives by the PCC, reduced amounts of additives to treat a surface of the PCC, and/or low moisture pick-up by the PCC.
  • the relatively lower surface area may contribute to a relatively lower viscosity of the material to which the PCC is added and/or a greater amount of “active” particles when used as a filler or additive, such as, for example, in polymer films.
  • a broad particle size distribution of the PCC may increase particle packing, whereas a steep or narrow particle size distribution of the PCC may decrease particle packing.
  • a relatively smaller PCC particle size may improve the gloss of a coating, such as, for example, a paper coating or paint, containing the PCC composition.
  • a relatively smaller particle size may also improve the impact resistance of a material, such as, for example, a molded product or coating, containing the PCC composition.
  • the steepness and/or cubicity of the PCC particles described herein may improve the handling properties of powders.
  • the steepness and/or cubicity of the PCC particles may improve the flowability of powders.
  • the PCC compositions described herein may have improved oil absorption properties. Improved oil absorption may, for example, improve the flowability of paints or powders incorporating the PCC compositions.
  • the PCC compositions may further comprise at least one active ingredient, encapsulated, absorbed, adsorbed, or embedded onto or into the polymorph of the PCC compositions for delivering said active ingredient to a delivery site.
  • the PCC compositions may provide a useful mechanism for delivering active ingredients, such as synthetic or natural nutritional or health products intact to where they are most effective.
  • the at least one active ingredient is homogeneously distributed throughout the PCC compositions.
  • the at least one active ingredient is heterogeneously distributed throughout the PCC compositions (i.e. concentrated near the surface of the PCC compositions).
  • the PCC compositions may be used for various applications, including but not limited to drug delivery, medical devices, biosensing, encapsulation, tracing, polymer fillers, cavitation enhancement in films, heavy metal sequestration, as a nucleation agent (for example, a foam nucleation agent), an abrasive, FGD feeds, synthetic paper component, or emulsion systems filler.
  • the PCC such as vaterite PCC
  • the PCC such as vaterite PCC
  • vaterite PCC may be used as a drug delivery agent or component.
  • vaterite may be used as a platform for small molecule or protein absorption or adsorption, such as into the pores of the vaterite.
  • vaterite may be used to encapsulate molecules including, but not limited to, insulin, bovine serum albumin, and lysozymes.
  • encapsulation may occur during a phase transition of the PCC from vaterite to calcite. Such encapsulation may promote controlled release of the encapsulated molecules.
  • encapsulation may occur through absorption or adsorption of the molecules into the pores of the vaterite.
  • encapsulation may occur through direct encapsulation during the formation of the PCC particles.
  • encapsulation may occur through hollow-centered PCC particles.
  • the PCC such as vaterite may be used as a controlled release agent.
  • vaterite may be exposed to highly acidic environments to control release. Vaterite exposed to such environments may break down, thereby releasing the encapsulant or encapsulated, absorbed, or adsorbed molecules.
  • the vaterite may serve as a template protein structure to control release of a molecule.
  • the vaterite may be used as a template for cross-linking polymer, such as, for example, biopolymers.
  • the polymers may be cross-linked using the vaterite as a template. Subsequent removal of the vaterite may result in a cross-linked polymer having a structure similar to the vaterite template (e.g., spherical).
  • the PCC such as vaterite
  • the PCC may be used in medical devices, such as, for example, implantable medical devices.
  • vaterite may exhibit rapid bioabsorption, for example, due to vaterite's high surface area. Because of rapid absorption, vaterite may be used as a calcium source for biological applications, such as, for example, bone regeneration.
  • Vaterite may also assist in the generation of bone minerals, such as phosphate bone minerals, such as hydroxyapatite.
  • the hydroxyapatite or other small molecules may be encapsulated by the vaterite or PCC, or may be bound (either chemically or physically) to the surface of the vaterite. Conversion of the vaterite to calcite, in some embodiments, may also promote binding of the PCC to bone.
  • the PCC such as vaterite
  • the PCC may be used in biosensing applications.
  • vaterite may be used in biosensing of pH changes or ion sensing.
  • a fluorescent pH sensor may be encapsulated by the vaterite, such as, for example, in tracing applications.
  • the PCC such as vaterite may be used as a filler for polymers.
  • the vaterite may be used in polymer films, such as, for example, cavitation enhancement.
  • the vaterite may promote more uniform cavitation of pores and may increase the breathability of the film.
  • PCC such as vaterite
  • metals such as heavy metals.
  • encapsulation may occur through a phase change from vaterite to calcite.
  • the PCC such as vaterite
  • the vaterite may be used as a nucleating agent.
  • the vaterite may act as a foam nucleating agent.
  • the PCC such as vaterite
  • the PCC may be used as an abrasive, such as, for example, a cleaning abrasive.
  • the PCC such as vaterite may be used as a feed material in an FGD process.
  • the increased surface area of the vaterite may improve reactivity and/or increase the reaction rate.
  • the vaterite may neutralize sulfuric acid generated in the FGD process.
  • the properties of the PCC compositions, such as vaterite, described in this disclosure may be beneficial for various applications.
  • a polymorph shift may be induced under shear and/or heat.
  • the vaterite may convert to needle-like particles or rhombic particles.
  • a polymorph shift may, in some embodiments, be influenced by the presence of surfactants or macromolecules.
  • a polymorph shift may also be influenced by inclusions in the vaterite structure, such as metals or other ions.
  • polymorph changes may be mitigated through the use of surfactants, reacting the vaterite in the presence of metals, or through the use of additives.
  • Additives may include, but are not limited to, acids or additives for biomineralization, such as, for example, ovalbumin, glutamic acid, or aspartic acid.
  • Gypsum or other sulfate was slurried in water at 35% solids or in a solution of 30-35% ammonium sulfate.
  • Ammonium carbonate was dissolved in water at elevated temperature in a concentration to give a 1:1.7 [gypsum: ammonium carbonate] molar ratio for reaction.
  • Alternative carbonate feeds were dissolved in water at room temperature in an amount to give a 1:1.7 [sulfate:carbonate] molar ratio for reaction.
  • the sulfate slurry and carbonate solution were mixed and allowed to react for at least 10 minutes.
  • the slurry was then filtered and the slurry cake washed with water. Reaction cake and decanted liquid were chemically and physically analyzed by FTIR, DSC, SEM, Sedigraph, and BET surface area analysis. Reactions involving this process are described in Table 1 and 2.
  • one or more of the methods disclosed in this disclosure may be used to precipitate PCC onto a core material.
  • the PCC may form a surface layer or coating that imparts beneficial properties to the core material.
  • the process may, in some embodiments, be used to precipitate a core material from solution where the precipitated core material has a PCC layer or coating.
  • layer or “coating” includes a precipitated calcium carbonate phase formed on at least a portion of the surface of the core material.
  • the PCC layer or coating may cover half or substantially all of the surface of the core material.
  • the core material may form the core of a calcium carbonate-coated composition.
  • the core material may include a weighting agent for use in drilling fluids.
  • the weighting agent may include iron oxide, such as, for example hematite (Fe 2 O 3 ).
  • Other weighting agents may be used, however, such as, for example, AgI, AgCl, AgBr, AgCuS, AgS, Ag 2 S, Al 2 O 3 , AsSb, AuTe 2 , BaCO 3 , BaSO 4 , BaCrO 4 , BaO, BeO, BiOCl, (BiO) 2 CO 3 , BiO 3 , Bi 2 S 3 , Bi 2 O 3 , CaO, CaF 2 , CaWO 4 , CaCO 3 , (Ca,Mg)CO 3 , CdS, CdTe, Ce 2 O 3 , CoAsS, Cr 2 O 3 , CuO, Cu 2 O, CuS, CU 2 S, CuS 2 , Cu 9 S 5 , CuFeS 2 , CusFeS 4 , Cu
  • the core material may include two or more homogeneous domains, such as, for example, (Ba,Sr)SO 4 , (Ba,Sr)CO 3 , or Ba(SO 4 ,CrO 3 ).
  • barium sulfate may be used as a weighting agent onto which calcium carbonate is precipitated.
  • weighting agents such as iron oxide and barium sulfate
  • weighting agents are denser than calcium carbonate and, therefore, provide a desirable densifying agent when added to fluids, such as drilling fluids.
  • fluids such as drilling fluids.
  • weighting agents on their own, also have a high hardness, which makes them abrasive to machinery and formations in the earth. As a result, the weighting agents may cause abrasion or corrosion of the machinery during us.
  • the relatively lower hardness of the calcium carbonate layer reduces the abrasivity of the weighting agent, which may reduce the abrasion caused during use of the agent.
  • the amount of the calcium carbonate coating may be tailored to provide a desired specific gravity of the resulting agent.
  • a PCC-coated hematite weighting agent may have an amount of PCC to provide a specific gravity of the PCC-coated hematite that is between the specific gravity of the calcium carbonate and the core material.
  • the modification of the specific gravity of the weighting agent may allow for tailoring the weighting agent to specific applications.
  • weighting agent may also be determined based on the intended application. For example, calcium carbonate and iron oxide are dissolvable in dilute acids, such as, for example, dilute hydrochloric acid (HCl). Choosing a weighting agent and coating with similar dissolution properties may permit removal of both the weighting agent and the coating to increase the flow of hydrocarbon by “shocking” the well with dilute acid to remove the weighting agent.
  • dilute acids such as, for example, dilute hydrochloric acid (HCl).
  • the precipitation of calcium carbonate onto various core materials also allows for a wider distribution of particle sizes in the weighting agent.
  • the particle size distribution may be controlled either by the size of the weighting agent or the amount of PCC used to coat the particles.
  • a method of precipitating calcium carbonate may include providing a core material in solution, adding calcium sulfate to the solution, adding a carbonate source to the solution, and precipitating calcium carbonate onto the core material.
  • the carbonate source may include ammonium carbonate.
  • the precipitated calcium carbonate may include a carbonate material containing calcium and at least one other metal.
  • the precipitated calcium carbonate may include dolomite (CaMg(CO 3 ) 2 ).
  • the core material may be dissolvable in dilute acid, such as, for example, hydrochloric acid (HCl).
  • dilute acid such as, for example, hydrochloric acid (HCl).
  • the core material may include a weighting agent.
  • the core material may include iron oxide, such as, for example hematite.
  • the core material may include barium sulfate.
  • the precipitated calcium carbonate may be between about 10% and about 25% by weight of the combined calcium carbonate and core material, such as, for example, between about 10% and about 15% by weight, between about 15% and about 20% by weight, between about 20% and about 25% by weight, between about 12% by weight and about 18% by weight, or between about 18% by weight and about 23% by weight of the combined calcium carbonate and core material.
  • the precipitated calcium carbonate-core composition may have a specific gravity in a range having a lower limit of about 2.6, 3, 4, 4.5, 5, or 5.5 to an upper limit of about 20, 15, 10, 9, 8, or 7, and permutations thereof.
  • the precipitated calcium carbonate-core composition may be suitable for use in a drilling application.
  • the precipitated calcium carbonate-core composition may be suitable for use as a weighting agent in a drilling fluid, such as an additive to a drilling mud.
  • An exemplary calcium carbonate coated hematite was prepared by reacting calcium sulfate with ammonium carbonate solution. First, 6.30 grams of calcium sulfate from Sigma Aldrich were mixed with 250 mL of water at 25° C. for 30 minutes for form a slurry. Next, 20 grams of the Hematite were added to the slurry and mixed to keep the specific ratio of 84.5% to 15.5% hematite to PCC by weight. Then 5.97 grams of ammonium carbonate were dissolved in 250 mL of water and immediately added to the slurry. The final mixture was mixed for 1 hr to precipitate the PCC onto the hematite. After mixing, the mixture was filtered and washed to remove excess ammonium sulfate. The resulting cake containing the PCC-coated hematite was recovered.

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