EP1814825A2 - Procédé destiné à produire des nanoparticules d'oxyde de fer - Google Patents

Procédé destiné à produire des nanoparticules d'oxyde de fer

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Publication number
EP1814825A2
EP1814825A2 EP05756032A EP05756032A EP1814825A2 EP 1814825 A2 EP1814825 A2 EP 1814825A2 EP 05756032 A EP05756032 A EP 05756032A EP 05756032 A EP05756032 A EP 05756032A EP 1814825 A2 EP1814825 A2 EP 1814825A2
Authority
EP
European Patent Office
Prior art keywords
particles
solution
iron
iron oxide
preferred
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP05756032A
Other languages
German (de)
English (en)
Inventor
Aharon Eyal
Asher Vitner
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Joma International AS
Original Assignee
Joma Chemical AS
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from IL162742A external-priority patent/IL162742A/en
Priority claimed from IL169384A external-priority patent/IL169384A0/en
Application filed by Joma Chemical AS filed Critical Joma Chemical AS
Publication of EP1814825A2 publication Critical patent/EP1814825A2/fr
Withdrawn legal-status Critical Current

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G49/00—Compounds of iron
    • C01G49/02—Oxides; Hydroxides
    • C01G49/08—Ferroso-ferric oxide [Fe3O4]
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82B—NANOSTRUCTURES FORMED BY MANIPULATION OF INDIVIDUAL ATOMS, MOLECULES, OR LIMITED COLLECTIONS OF ATOMS OR MOLECULES AS DISCRETE UNITS; MANUFACTURE OR TREATMENT THEREOF
    • B82B3/00—Manufacture or treatment of nanostructures by manipulation of individual atoms or molecules, or limited collections of atoms or molecules as discrete units
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G49/00—Compounds of iron
    • C01G49/02—Oxides; Hydroxides
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G49/00—Compounds of iron
    • C01G49/02—Oxides; Hydroxides
    • C01G49/06—Ferric oxide [Fe2O3]
    • 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
    • C09C1/22—Compounds of iron
    • C09C1/24—Oxides of iron
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2002/00—Crystal-structural characteristics
    • C01P2002/04—Compounds with a limited amount of crystallinty, e.g. as indicated by a crystallinity index
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/10—Particle morphology extending in one dimension, e.g. needle-like
    • C01P2004/12—Particle morphology extending in one dimension, e.g. needle-like with a cylindrical shape
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/30—Particle morphology extending in three dimensions
    • C01P2004/32—Spheres
    • 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
    • C01P2004/62—Submicrometer sized, i.e. from 0.1-1 micrometer
    • 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
    • C01P2004/64—Nanometer sized, i.e. from 1-100 nanometer
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/12—Surface area

Definitions

  • the present invention relates to a method for producing iron oxide nano- particles and more particularly, to a methodfor producing iron oxide particles of desired particle size, particle size distribution and habit in an industrially and economically useful manner.
  • iron oxide means and includes iron oxides of the formula Fe x Oy (e.g. Fe 2 O 3 as in hematite and magnetite), iron hydroxi- oxides of the formula Fe p (OH) q O r (e.g. FeOOH, as in goethite and akaganeite) various hydration forms of those and compositions wherein those are major components, wherein x, y, p, q, r are each whole integers.
  • iron oxides powders are widely used in industry for various applications: magnetic data storage materials, catalysts, inorganic pigments and precursor for ferrite synthesis.
  • hydrothermallurgic synthesis of ultra fine iron oxide powders iron hydroxide, formed in neutral or alkali solutions, is mostly used as a precursor.
  • the preparation of iron (III) oxide from homogeneous acidic solutions at elevated temperature has been noticeably less studied.
  • Iron oxides come in variety of size, color, density, porosity, surface area and shape. Those parameters have a big impact on their uses and performance.
  • the final product properties depend on the procedures developed for precipitation and aging of the products.
  • Iron oxide nano-particles exhibit color varying from yellow to yellow brown (limonite and goethite), light red to deep red (hematite), orange (lepidocrotite) and brown (Akaganeite).
  • the color of each iron oxide depends upon particle size, particle size distribution and habit.
  • hematite particles have different colors varying from light red to deep red.
  • Hematite particles having a larger particle size tend to exhibit a deeper hue.
  • An object of the present invention is to provide an industrially and economically feasible process for producing iron oxide particles of desired particle size, size distribution and habit.
  • the particles produced in that manner are easy to transform by heating into other iron oxide type particles of lower hydration level thus obtaining particles with high porosity and of the required type, morphology, crystal size, crystal size distribution and habit.
  • a process for producing iron oxide particles in aqueous solution which comprises maintaining an aqueous ferrous salt solution at a temperature lower than 55°C. for a time sufficient to reduce the pH of solution by at least 0.2 pH units due to hydrolysis.
  • the resulting solution is then subjected to a modification in temperature and/or Fe(III) concentration (dilution) and or addition of a reagent thus increasing the pH of the solution.
  • the preferred modification of said parameters is at a high rate.
  • said solution is kept at said modified conditions for at least 0.5 minute.
  • Preferably said modification of conditions is carried out over a period of up to 1 hour.
  • said process produces at least 50 kilograms of particles per hour.
  • Preferably said modification of conditions is carried out at a pressure of up to 100 atmospheres.
  • said method is further characterized in that the majority of the formed particles have a degree of crystallinity of less than 50%.
  • Preferably said method is further characterized in that the size ratio between the smallest and biggest particle of 50% of the formed particles is less than about 10.
  • said method is further characterized in that the size ratio between the smallest and biggest particle of 50% of the formed particles is less than about 5.
  • said method is further characterized in that the majority of the formed particles are of a configuration other than elongated.
  • said method is further characterized in that the majority of the formed particles have a configuration wherein the ratio between one dimension and any other dimension is less than about 3. In other preferred embodiments of the present invention the majority of the formed particles are of an elongated configuration.
  • the majority of the formed particles have a surface area of at least 30 m 2 /gr.
  • the majority of the formed particles have a surface area of at least 100 m 2 /gr.
  • said method preferably further comprises the step of removing part of the water in said particle suspension after said facilitating and prior to, simultaneously with or after said dehydrating.
  • said dehydrating is preferably conducted under super-atmospheric pressure.
  • the temperature of said particle suspension is preferably elevated to said dehydrating temperature over a period of up to 2 hours.
  • the majority of the dehydrated particles are preferably of a configuration other than elongated.
  • the majority of the dehydrated particles preferably have a surface area of at least 30 m 2 /gr.
  • said particles are selected from the group consisting of goethite hematite and magnetite. Especially preferred are particles having the formula of FeOOH.
  • particles having the formula Fe 2 O 3 .3H 2 O are also preferred.
  • said preparation of an aqueous solution involves oxidation.
  • the pH of said aqueous solution is between about 1.0 and about 5 during at least a fraction of said facilitating step.
  • aqueous solution is between about 1.5 and about 4 during at least a fraction of said facilitating step.
  • Most preferred is a method wherein the pH of said aqueous solution is between about 1.7 and about 2.5 during at least a fraction of said facilitating step.
  • said preparation of an aqueous solution involves oxidation of ferrous ions.
  • said oxidation uses an oxidant selected from a group consisting of oxygen, hydrogen peroxide, nitric acid and nitrate.
  • Preferably said oxidation is conducted in a solution comprising sulfuric acid and nitric acid.
  • said oxidation is chemically or biologically catalyzed.
  • said preparation of an aqueous solution involves dissolution of an iron compound.
  • said iron compound is preferably selected from the group consisting of iron salts, iron oxides, iron hydroxides, iron minerals and combinations thereof.
  • said iron compound is selected from the group consisting of iron oxides, iron hydroxides, minerals containing the same and mixtures thereof and said compound is dissolved in an acidic solution comprising an acid selected from the group consisting of sulfuric acid, nitric acid, hydrochloric acid, phosphoric acid, their acidic salts and combinations thereof.
  • said prepared aqueous solution comprises an anion selected from the group consisting of sulfate, chloride, nitrate, phosphate and mixtures thereof.
  • said modification comprises at least two heating steps.
  • At least one heating step is preferably conducted by contacting with a warmer stream selected from a group consisting of hot aqueous solutions, hot gases and steam.
  • said method preferably further comprises grinding formed particles.
  • said method preferably further comprises screening formed particles.
  • said method preferably further comprises hydrogenating formed particles.
  • the present invention is also directed to iron oxide particles whenever formed according to the above-defined methods and products of their conversion.
  • the present invention is further directed to a preparation comprising said particles.
  • said particles are preferably dispersed in a liquid, supported on a solid compound or agglomerated to larger particles.
  • a process for the production of a preparation as defined above comprising steps selected from the group consisting of dispersing said particles, addition of a support, heat treatment, mixing, water evaporation and combinations thereof.
  • said particles and preparations are used in the manufacture of a paint.
  • said particles and preparations are used in the manufacture of a catalyst.
  • the formed particles comprise FeOOH 1 Fe 2 O 3 , Fe(OH) 3 , Fe 3 O 4 or a combination thereof.
  • the modified solution stays in mixing chamber for less than 5 seconds and in a more preferred embodiment the modified solution stays in the mixing chamber for less than 1 second.
  • the mixing in the mixing chamber is carried out using the flow rate of the entering solution or by using a mechanical mode of mixing or another mode of mixing.
  • the modified solution exits the mixing chamber in a plug flow mode.
  • the plug flow continues for more then 0.1 second and in a most preferred embodiment the plug flow contineues for more then 5 seconds.
  • the solution exiting the plug flow enters into a vessel.
  • the solution in the vessel is mixed.
  • the starting aqueous iron salt solution used in the present invention is preferably an aqueous iron salt solution comprising ferric ions or their complexes at a concentration of at least 0.1 % w/w iron and at pH greater than about 1.5.
  • the iron w/w concentration in the starting solution is at least 1 %, more preferably at least 5%, most preferably at least 10%. There is no upper limit to the concentration of the starting solution. Yet, according to a preferred embodiment, the concentration is below the saturation level. High viscosity is not desired according to another preferred embodiment.
  • the pH of the starting solution is at least 1.7, preferably at least 1.9.
  • the pH of the prepared starting solution is acidic or neutral, e.g. as determined by the OH/Fe ratio in the solution. According to a preferred embodiment, that ratio is smaller than 3, more preferably smaller than 2.5.
  • the temperature of the prepared starting solution is less than 55 0 C.
  • Any source of iron is suitable for preparing the starting solution of the present invention, including various scrap irons such as chopped scrap iron or the like, iron containing ores, fractions of such ores, products of their processing, iron salts or iron containing solutions such as aqueous solution exiting iron containing ores.
  • step (b) is conducted shortly after both the desired concentration and pH are achived.
  • the solution used in step (b) was prepared within a short time and does not contain ferric ions or their complexes, which were prepared at different times and then mixed together. For a similar reason, extended preparation time is not desired.
  • preparation time is shorter than 20 hours, preferably shorther than 10 hours, most preferably shorter than 2 hours.
  • an older solution exists (e.g. a recycled solution) and is desired to be mixed with a fresh solution to form the starting solution, the older solution is first acid treated, as described ihereinafter.
  • the freshly prepared ferric salt solution may contain any anion, including chloride, sulfate, nitrate phosphate, carboxylate, organic acid anions, and various mixtures thereof, etc.
  • the freshly prepared solution comprises ferric sulfate.
  • the salt is of an organic acid.
  • a freshly prepared salt solution for use in the process of the present invention may be a solution that was produced (in natural conditions, such as solutions exiting mines with iron containing ores) or a solution that was prepared by artificial methods including chemical or biological oxidations.
  • a solution could be prepared by various methods or their combinations, including dissolution of ferric salts, dissolution of ferrous salts, dissolution of double salts, dissolution of iron oxide-containing ores in an acidic solution, dissolution of scrap iron in oxidizing solutions, such as solutions of ferric salt, nitric acid, etc., leaching of iron-containing minerals, such as pyrite and chalcopirite, etc.
  • Preparing the aqueous solution is conducted in a single step, according to a preferred embodiment.
  • the preparation comprises two or more steps.
  • a concentrated solution of ferric salt is prepared, e.g. by dissolution of a salt in water or in an aqueous solution. While momentarily and/or locally, during the dissolution, the required pH and concentration of the starting solution are reached, typically the pH of the formed concentrated solution after at least partial homogenization is lower than desided for the starting solution. According to a preferred embodiment, such momentary reaching the desired conditions is not considered preparation of the starting solution.
  • the pH of the concentrated solution is then brought to the desired level by any suitable means, such as removal of an acid, addition and/or increasing the concentration of a basic compound, or a combination of those.
  • the formation of the starting solution in that case is considered the adjustment of the pH to the selected range, according to a preferred embodiment, and the pH of the starting solution is the one obtained after at least partial homogenization, according to another preferred embodiment.
  • a concentrated solution is prepared and the pH is adjusted to a level that is somewhat lower than desired.
  • the starting solution is then prepared by dilution of the solution, which increases the pH to the desired level.
  • the pH of the starting solution is the one obtained after at least partial homogenization, according to a preferred embodiment.
  • the same is true for other methods of multi-stage preparation of the starting solution, as e.g. in the case of forming a solution of a ferrous salt and oxidizing it to form a solution of a ferric salt.
  • the iron source for the solution may be scrap iron or the like and/or iron (II) and an oxidation step must be performed in order to obtain the ferric solution.
  • oxidation may use any known oxidant, such as air, oxygen, hydrogen peroxide, nitric acid and nitrate and their combinations. Oxidation could be done at any temperature and pressure. Typically, elevated temperature and elevated pressure accelerate the oxidation reaction. A biological catalyst, a chemical catalyst or a combination thereof could be used. Complete oxidation is not required and the particles of the invention could be formed from a solution containing both ferric and ferrous ions.
  • the starting solution is freshly prepared.
  • the solution does not comprise ions and/or complexes prepared at different times, as in the case of mixing a recycled solution with a freshly prepared one.
  • pH lower than 1.5 high concentration (e.g. above 10% iron) and low temperatures (e.g. lower than 4O 0 C)
  • a solution maintains its fresheness for a longer time, and could serve as a stock solution, according to a preferred embodiment.
  • the solution is not considered fresh after a few hours or a few days, according to another preferred embodiment..
  • freshness of the solution is regained by acid treatment.
  • Such less fresh solution is acidulated to pH lower than 2.0, preferably to a pH lower than 1.5 and is preferably mixed, agitated or shaken for at least 5 nriin, before increasing the pH back to above 1.7 to reform a fresh solution.
  • Such reformed fresh solution is mixed with other fresh solution according to a preferred embodiment.
  • the ferric solution is preferably retained at a temperature lower than 55 0 C for a retention time that doesn't exceed IOdays.
  • hydrolysis takes place.
  • the retention time is sufficient for the pH to decrease by at least 0.2 units due to said hydrolysis.
  • the retention time is the time needed to produce at least 1 millimolar H+ (protons) in solution.
  • the retention time is the time required to form in the solution 0.0001 mole of proton ions per mole of Fe(III) in the solution, more preferably 0.001 mole of proton ions per mole of Fe(III) in the solution.
  • the retention time is the time that would have been needed to form those amounts of protons with no base addition.
  • the retention time decreases with increasing pH of the prepared solution.
  • the retention time is preferably from 1 hour to few days.
  • the retention time is preferably less than 1 day. In cases of varying pH during the retention time, the latter is affected by the maximal pH reached.
  • retention time decreases with increasing temperature of the solution.
  • the third step needed in order to achieve the above mode of precipitation is modifying the conditions of the solution to achieve at least one of an increase in pH and/or temperature and or dilution of the solution.
  • the modification of conditions is preferably done in a short time and the modified conditions are maintained for a short time.
  • the duration at the modified conditions is less than 24 hours, according to an examplary embodiment, preferably less than 4 hours, more preferably less than 1 hour, most preferably less than 10 minutes.
  • the modification of conditions is conducted within 1 hour, prefereably within 10 minutes, more preferably 1 minute.
  • Increasing the pH in step (c) can be achieved by any known method, such as removal of an acid or addition of or increasing the concentration of a basic compound. Acid removal can be conducted by known methods, such as extraction or distillation. Any basic compound could be added.
  • a basic compound is a compound that is more basic than ferric sulfate, as measured by comparing the pH of their equi-molar solutions.
  • such basic compound is preferably at least one of an inorganic or organic base or precursor of a base, e.g. an oxide, hydroxide, carbonate, bicarbonate, ammonia, urea, etc.
  • the basic compound is ferrous salt such as ferrous sulfate.
  • ferrous sulfate is formed in situ by introducing metalic iron.
  • Such methods of increasing pH are also suitable for use in step (a) of preparing the starting solution.
  • basic pH is avoided through most of the process, so that pH increase in step (c) is conducted so that during most of the duration of that step, the pH is acidic, or slightly acidic.
  • the solution is diluted in step (c).
  • dilution is by at least 20%, more preferably at least 100% most preferably at least 200%.
  • the temperature of the solution is increased.
  • temperature is increased by at least 1O 0 C, more preferably at least 3O 0 C most preferably at least 5O 0 C.
  • Temperature increase can be affected by any known method, such as contact with a hot surface, with hot liquid, with hot vapors, infra-red irradiation, microwaving or a combination of those.
  • the basic compound is added to the solution of the ferric salt after the retention time, in an aqueous solution, which also dilutes the ferric salt.
  • the solution of the ferric salt is contacted with a diluting solution comprising water and/or an aqueous solution, which is of a temperature greater than the solution of the ferric salt solution by at least 5O 0 C according to a first preferred embodiment, preferably by at least 100 0 C.
  • the temperature of said diluting solution is between about 100 0 C and 25O 0 C, between 100 0 C and 18O 0 C according to a preferred embodiment and between 15O 0 C and 250 0 C, according to another preferred embodiment.
  • the diluting solution comprises a reagent that interacts with ferric ions, their complexes and/or with particles containing those.
  • the ferric salt solution after the retention time is combined in step (c) with a second aqueous solution comprising a solute that is more basic than the ferric salt, which second solution is at a temperature greater than the solution of the ferric salt.
  • the ferric salt solution and said second solution are mixed, e.g. mechanically, in a suitable equipment that provide for strong mixing to achieve rapidly an homogenous system.
  • the mixing equipment is preferably selected so that it withstands super-atmospheric pressure.
  • the mixing is conducted by contacting flowing ferric salt solution with flowing second aqueous solution, e.g. in a plug-flow mode.
  • the mixed stream is kept at the formed temperature or at another temperature obtained by cooling or heating for a short duration, less than 1 day according to an examplary embodiment, preferably between 1 and 60 minutes, more preferably between 3 and 15 minutes.
  • the degree of heating, pH elevation and dilution when conducted as a single means for modification or in combination, affects the chemical nature of the formed particles. For example, typically, the higher the temperature, the lower is the degree of hydration of the particle components. The crystal form and shape are also affected. Thus, the conditions selected for Example 1, lead to spherical particles.
  • the final product oxide is formed in step (c) of the process.
  • the product of step (c) is further processed and transformed to the desired final product.
  • ferric hydroxide in the particles is transformed, according to a preferred embodiment, to goethitie or hematite.
  • Such further processing comprises heating, according to a preferred embodiment.
  • heating is to a temperature in the range between about 6O 0 C and 800 0 C.
  • heating is of a solution comprising the formed particles as obtained in step (c), or after some treatment, e.g. partial removal of water.
  • the formed particles are first separated from the solution.
  • the separated particles could be treated as such or after further treatment, e.g. washing and/or drying.
  • Heating in solution is preferably done at a super-atmospheric pressure and in an equipment suitable for such pressure.
  • an external pressure is applied.
  • the nature of heating is also a controlling factor, so that the results of gradual heating is in some cases different from rapid heating.
  • step (c) and further heating are conducted sequentially, preferably in the same vessel.
  • the crystal habit of the transformed particles is of the general habit of the origin particles from which it was produced, according to a preferred embodiment.
  • rod-like goethite particles can be transformed to elongated hematite particles, or in another embodiment of the present invention amorphous particles with low particle dimension ratio can be transformed to goethite of low particle dimension ratio.
  • agglomerates with rod-like habit or agglomerates of spherical habit can be transformed into goethite or hematite particles with rod-like habit or agglomerates with spherical habit, respectively..
  • the present invention provides conditions for the production of precipitates which are easy to transform as well as providing a transformation product with superior properties.
  • At least one dispersant is present in at least one of the method steps.
  • the term dispersant means and includes dispersants, surfactants, polymers and rheological agents.
  • a dispersant is introduced into a solution in which a ferric salt is dissolved or is to be dissolved, or is added to a precursor of the solution, such as a mineral ore, according to a preferred embodiment.
  • a dispersant is added to the solution during the retention time or after it.
  • a dispersant is added to the solution prior to the adjustment step or after such step.
  • a dispersant is added prior to a transforming step, during such step or after it.
  • the process further comprises a step of modifying the concentration and/or the nature of the dispersant during the process and/or another dispersant is added.
  • suitable dispersants are compounds having the ability to adsorb on the surface of nanoparticles and/or nuclei.
  • Suitable dispersants include cationic polymers, anionic polymers, nonionic polymers, surfactants poly-ions and their mixtures.
  • the term "dispersant" relates to molecules capable of stabilizing dispersions of the formed particles, and/or modifying the mechanism of formation of the nanoparticles, and/or modifying the structure, properties and size of any species formed during the process of formation of the nanoparticles.
  • said dispersant is selected from a group consisting of polydiallyl dimethyl ammonium chloride, Sodium- carboxy methyl cellulose, poly acrylic acid salts , polyethylene glycol, and commercial dispersants such as Solsperse grade, Efka grades, Disperbyk or Byk grades , Daxad grades and Tamol grades (trade names).
  • the process further comprises a step of ultrasound treating the solution during or after at least one of the process steps.
  • the process further comprises a step of microwave treating the solution during or after at least one of the process steps.
  • further processing comprises reducing iron oxide in the formed particles from Fe(III) to Fe(II) or to metal iron.
  • Reduction is partial according to a preferred embodiment and approaches completion according to another. Any reducing agent could be used, e.g. hydrogen.
  • reduction is conducted as a separate step, according to an alternative embodiment, reduction is conducted as part of a process of converting the particles into a final product, such as a catalyst.
  • further processing comprises partially fusing particles to particles of greater size.
  • aggregates of the particles are mechanically treated for comminuting.
  • the product of the present invnention, as formed in step (c) or after further transformation, is preferably small-size paticles of iron oxide.
  • the particles size is in the range between 2nm and 500nm, according to a preferred embodiment.
  • the size distribution of the the product particles is narrow so that the size ratio between the smallest and biggest particle of 50% of the formed particles is less than about 10, more preferably less than 5, most preferably less than 3.
  • Separate particles are formed according to a preferred embodiment.
  • the formed particles are at least partially agglomerated.
  • the majority of the formed particles have a degree of crystallinity of less than 50% as determined by X-ray analysis.
  • the shape of the particles formed in step (c) or after further transformation is elongated, such as in needles, rods or rafts.
  • the particles are spherical or nearly spherical, so that the majority of the formed particles have a configuration wherein the ratio between one dimension and any other dimension is less than about 3.
  • the majority of the formed particles have a surface area of at least 30 m 2 /gr, more preferably at least 100 m 2 /gr.
  • High surface area particles of the present invention are suitable for use in catalyst preparation.
  • the process of the present invention is capable of forming highly pure iron oxide from a precursor of relatively low purity, such as an iron ore, e.g. pyrite or chalcopyrite.
  • a precursor of relatively low purity such as an iron ore, e.g. pyrite or chalcopyrite.
  • the purity with regards to other metals of at least 95%, more preferably at least 99%. .
  • the iron oxide particles are doped with ions or atoms of other transition metals.
  • the particles are obtained in a form selected from a group consisting of particles dispersed in a liquid, particles supported on a solid compound, particles agglomerated to larger particles, partially fused particles, coated particles, or a combination thereof.
  • the particles, their preparation and/or products of their conversion are suitable for use in many industrial applications, such as in production of pigments, catalysts, coatings, Thermal coating etc.
  • the particles are used in those and other applications 0683
  • the method of the present invention is highly suitable for economically attractive industrial scale production. According to a preferred embodiment, the method is operated at a rate of at least 50 Kg/hour, more preferably at least 500Kg/hour, most preferably at least 5tons/hour.
  • the pH of the solution drops during the process due to the hydrolysis of the ferric salt and thereby formation of an acid, e.g. sulfuric acid.
  • an acid e.g. sulfuric acid.
  • Such acid is reused according to a preferred embodiment, e.g. for the formation of the ferric salt solution, e.g. in dissolution of an iron-containing mineral.
  • the formed acid is partially or fully neutralized during the process, forming thereby a salt of the acid.
  • the salt is of industrial use, e.g. as in the case where neutralization is done with ammonia to form ammonium salts suitable for use as fertilizers.
  • At least partially dehydrated small-size iron oxide particles are formed.
  • the method comprises the steps of preparing a starting aqueous solution comprising ferric ions or complexes thereof, at a concentration of at least 0.1% w/w iron, which solution has pH of at least 1.2; preparing a modifying aqueous solution of a temperature greater than 8O 0 C; contacting the starting solution with the modifying solution to form a modified system and retaining the modified system at a temperature greater than 8O 0 C for at least 0.5 minute.
  • the majority of the formed particles are between about 2nm and about 500nm in size and comprise FeOOH, Fe 2 ⁇ 3 , Fe 3 O 4 Or a combination thereof.
  • Preparing the starting solution may use methods similar to those described above.
  • the iron concentration in said starting solution is greater than 2%.
  • the pH of the starting solution is at least 1.5, more preferred at least 1.7.
  • the OH/Fe molar ratio in the starting solution is at least 0.05.
  • the temperature of the modifying solution is in the range between 100 0 C and 300 0 C.
  • At least one of the starting solution and modifying solution comprises according to a preferred embodiment a reagent that is capable of interacting with ferric ions, their complexes or with particles containing those.
  • said reagent is a dispersants or a basic compounds.
  • the basic compound is preferably ammonia, ammonium carbonate, ammonium bicarbonate or urea.
  • basic pH is avoided in the modifid solution.
  • the OH/Fe molar ratio in the solution of said mofidied system is less than 3, more preferably between 0.5 and 2.
  • the temperature of the modified solution is determined by the temperatures of the starting solution and of the hot modifying solution, by their heat capacity and by their relative amounts. According to a preferred embodiment, the temperature of the modified solution is kept with minimal changes, e.g. with no changes greater than 2O 0 C. According to a preferred embodiment the modified system is retained at that temperature for a duration of between 1 and 30 minutes, more preferably between 3 and 15 minutes.
  • the starting solution is maintained for a preliminary retention time before said contact with the modifying solution.
  • the solution is kept at a temperature of less than 55 0 C and pH greater than 1.5.
  • the duration of the preliminary retention time is sufficient for the pH to decrease by at least 0.2 units, but does not exceed 14 days, according to a preferred embodiment.
  • the particles formed in the process are subjected to steps selected from a group consisting of dispersing said particles, addition of a support, heat treatment, mixing, water evaporation, spray drying, thermal spraying and a combination thereof.
  • a starting aqueous solution comprising at least one of ferric ions and complexes thereof, at a concentration of at least 0.1% w/w iron, which solution has pH of at least 1.2 is prepared.
  • a modifying aqueous solution of a temperature greater than 8O 0 C and the starting solution are contacted in a continuous mode in a mixing chamber to form a modified system.
  • the mixing chamber is built in a way to ensure quick and efficient mixing of the solutions.
  • the modified solution is removed from the mixing chamber in a plug-flow mode. During the plug flow the precipitation is completed or in another preferred embodiment the solution is not exhausted during the plug flow time and the precipitation continues in another vessel.
  • the mixing in the mixing chamber is preferably carried out using the flow rate of the entering solution or by using mechanical mixing means or another mode of mixing.
  • the temperature in the mixing chamber and during the plug flow are similar. In another preffered embodiment the temperature of the solution during the plug flow is higher than in the mixing chamber and in yet another preferred embodiment the temperature of the solution during the plug flow is lower than in the mixing chamber.
  • the residence time in a mixing chamber is less than about 5 minutes and more preferred is a residence time of less than 1 minute. In an even more preferred embodiment, the residence time in a mixing chamber is less than about 5 seconds and in an especially preferred embodiment the residence time is less than 1 second. 000683
  • the solution exiting the plug flow enters into a vessel.
  • the solution in the vessel is mixed.
  • the conditions in the solution were adjusted by adding, while vigorously mechanicaly stirring at 600 rpm, to 900gr water at 8O 0 C, which dilutes, the solution, heats it and increases it pH. After 10min, the mixing was stopped. Particles were observed. After settling for 1 hour, the clear liquid phase was removed. The precipitate was washed 3 times with water and then centrifuged.
  • Example 2 100gr fresh solution of 0.25M Fe 2 (SO 4 ) 3 was prepared and retained at 25 0 C as in Example 1. The solution was added while vigorously mechanically stirring at 600 rpm to 900gr water at 122 0 C in a pressure vessel at a formed pressure of about 2 atmospheres. After 30min, the mixing was stopped and particles were observed. The particles suspension was allowed to cool to room temperature and a precipitate was observed. The precipitate was separated and washed 3 times with water and then centrifuged.
  • the obtained material was in the form of ultra fine mono-dispersed powder of FeOOH.
  • the particles were spherical and with average dimension ratio of about 1.5.
  • Example 1 The procedure in Example 1 was repeated with one difference.
  • the 900gr hot water contained 0.1% dispersant - poly(diallyldimethylammonium chloride) (PDAC) with molecular weight range of 200,000 to 300,000. After 10min, the mixing was stopped. A suspension of particles was observed. The particles did not settle during standing for an hour. Particles were separated by centrifugation and washed as in Example 1. The formed particles are similar to those in Example 1.
  • PDAC poly(diallyldimethylammonium chloride)
  • IOOOgr fresh solution of 0.25M Fe 2 (SO 4 ) 3 (about 2.8% iron) was prepared by dissolving Fe 2 (SO-O 3 crystals in water. Ammonia was added to 100gr samples of the solution to reach NH 3 /Fe molar ratio of 1. The solution was kept at 25 0 C for various retention times (T ret ). After the retention time, ach of the formed solutions was mixed with 900gr water, containing - in some of the cases - 0.25% dispersant (PDAC) at various temperatures and kept in a Parr unit (high pressure vessel) with vigorous mechanical stirring at 600 rpm. After 5min, the stirring was stopped. Particles were observed and separated from the solution by centrifugation. The precipitate was washed 3 times with water and then centrifuged. 683
  • Deviation (50%)* the particle size range of 50% of the particles around the average size (nm). * The particles in the samples that do not contain dispersants are condensed in aggregates while those with dispersant are loosely attached to each other
  • Example 5 IOOOgr fresh solution of 25% Fe 2 (SO 4 ) 3 was prepared by dissolving Fe 2 (SO 4 ) 3 crystals in water. Ammonia was added to 100gr samples of the solution to reach various NH 3 /Fe molar ratios. The solutions was kept at 25 0 C for various retention times (T ret ). After the retention time, ach of the solutions was added, to 900gr water at 85 0 C, containing 0.1% dispersant (PDAC), while vigorously stirring. After 10min, the stirring was stopped. Particles were observed. The solution was removed and centrifuged. The precipitate was washed 3 times with water and then centrifuged.
  • PDAC dispersant
  • the obtained materials were analyzed by SEM photographs. In all cases, the particles were distorted rods of large size distribution.
  • 225gr water portions were pumped through a heat exchanger which was placed in an oil bath at 150 0 C or 19O 0 C, into a 0.25ml mixing chamber.
  • 25gr of each Fe 2 (SO 4 ) 3 solution after retention was simultaneously pumped into the same mixing chamber, where it was mixed with the pre-heated water to form modified solutions.
  • Each of the modified solutions was then flowing through a 50ml heated tube (placed in the same oil bath) into the Parr unit (high pressure vessel) in which the temperature was kept the same as in the oil bath and mixing chamber. After additional 5 min, the mixing was stopped and the solution was removed from the Parr and cooled. The solution was centhfuged and the clear liquid phase was removed. The precipitate was washed 3 times with water and centrifuged.
  • the conditions in the solution were adjusted by adding, while vigorously mechanically stirring at 600 rpm to 900gr water at 8O 0 C, which dilutes, the solution, heats it and increases it pH. After 10min, the mixing was stopped. Particles were observed. After settling for 1 hour, the clear liquid phase was removed. The precipitate was washed 3 times with water and then centrifuged.
  • the obtained material was in the form of ultra fine mono-dispersed powder of Fe(OH) 3 .
  • SEM photographs indicate that the particle are spherical with uniform particle size of about 40nm.

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Abstract

L'invention concerne un procédé destiné à former des particules d'oxyde de fer de petite taille et consistant à préparer une solution de départ aqueuse renfermant des ions ferriques et/ou des complexes correspondants avec une concentration supérieure ou égale à 0,1% poids/poids de fer et un pH supérieur à environ 1,5, à maintenir cette solution à une température inférieure à 55°C pendant un temps de séjour dans lequel se produit une hydrolyse, l'effet de cette hydrolyse étant suffisant pour réduire le pH d'au moins 0,2 unités, cette période ne dépassant pas 14 jours, en vue de la formation d'un système contenant une solution modifiée, et à ajuster les conditions dans ce système au moyen d'au moins une opération choisie parmi le chauffage de la solution modifiée en vue d'en élever la température d'au moins 10°C, l'élévation du pH de la solution modifiée d'au moins 0,3 unités, et la dilution de la solution modifiée d'au moins 20%. On forme ainsi des particules dont la majorité présente une taille comprise entre environ 2 nm et environ 500 nm.
EP05756032A 2004-06-27 2005-06-27 Procédé destiné à produire des nanoparticules d'oxyde de fer Withdrawn EP1814825A2 (fr)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
IL162742A IL162742A (en) 2004-06-27 2004-06-27 Method for producing iron oxide nano particles
IL16722505 2005-03-03
IL169384A IL169384A0 (en) 2005-06-23 2005-06-23 A method for producing iron oxide nano particles
PCT/IL2005/000683 WO2006001018A2 (fr) 2004-06-27 2005-06-27 Procede destine a produire des nanoparticules d'oxyde de fer

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KR (1) KR20070044817A (fr)
AU (1) AU2005257059A1 (fr)
BR (1) BRPI0511319A (fr)
CA (1) CA2572190A1 (fr)
EA (1) EA200700135A1 (fr)
MX (1) MX2007000357A (fr)
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WO (1) WO2006001018A2 (fr)

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JP5596539B2 (ja) 2007-05-21 2014-09-24 オーバイト アルミナ インコーポレイテッド アルミニウム鉱石からアルミニウム及び鉄を抽出する方法
KR100881456B1 (ko) * 2007-12-07 2009-02-06 주식회사 잉크테크 산화 은의 제조방법
KR101124224B1 (ko) * 2010-02-17 2012-03-27 한국화학연구원 칼코파이라이트형 나노입자의 제조방법
WO2012000529A1 (fr) 2010-07-01 2012-01-05 Max-Planck-Gesellschaft zur Förderung der Wissenschaften e. V. Procédé pour préparer des nanoparticules de magnétite ou de maghémite ayant une taille contrôlée en utilisant des conditions douces
BR112013023907A2 (pt) 2011-03-18 2019-09-24 Orbite Aluminae Inc processo de recuperação de ao menos um elemento terra-rara a partir de um material contendo alumínio
BR112013028371A2 (pt) 2011-05-04 2017-02-14 Orbite Aluminae Inc processo de recuperação de ao menos um elemento terra-rara e/ou de ao menos um metal raro selecionado dentre in, zr, li e ga a partir de ao menos um material
RU2013157943A (ru) 2011-06-03 2015-07-20 Орбит Элюминэ Инк. Способ получения гематита
JP2014526431A (ja) 2011-09-16 2014-10-06 オーバイト アルミナ インコーポレイテッド アルミナ及び様々な他の生成物の調製プロセス
EP2802675B1 (fr) 2012-01-10 2020-03-11 Orbite Aluminae Inc. Procédés de traitement de boue rouge
CA2903512C (fr) 2012-03-29 2017-12-05 Orbite Technologies Inc. Procedes de traitement de cendres volantes
CN102659191B (zh) * 2012-05-22 2014-03-26 中北大学 一种控制四氧化三铁形貌与性能的方法
RU2597096C2 (ru) 2012-07-12 2016-09-10 Орбит Алюминэ Инк. Способы получения оксида титана и различных других продуктов
WO2014047728A1 (fr) 2012-09-26 2014-04-03 Orbite Aluminae Inc. Procédés pour la préparation d'alumine et de chlorure de magnésium par lixiviation par hcl de divers matériaux
BR112015011049A2 (pt) 2012-11-14 2017-07-11 Orbite Aluminae Inc métodos para purificação de íons de alumínio
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KR20070044817A (ko) 2007-04-30
CA2572190A1 (fr) 2006-01-05
MX2007000357A (es) 2008-03-13
JP2008504202A (ja) 2008-02-14
WO2006001018B1 (fr) 2006-08-24
EA200700135A1 (ru) 2007-08-31
BRPI0511319A (pt) 2007-12-04
WO2006001018A3 (fr) 2006-06-22
AU2005257059A1 (en) 2006-01-05
NO20070512L (no) 2007-02-15

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