MXPA97004235A - Method to separate a mixture of minerals finally divided - Google Patents

Abstract

The present invention relates to a method for the selective separation of finely divided mineral particles in a mixture of mineral particles, comprising: (a) forming the mixture in a dispersed aqueous pulp, (b) adding to the dispersed aqueous pulp. , a fatty acid and a source of polyvalent cations, unless at least one of the minerals in the pulp provides source polyvalent cations, without flocculating the pulp, (c) without adding a light foaming agent to the pulp, incorporate a high molecular weight organic anionic polymer, thus forming flocs that settle as a dense bottom layer; (e) and separate the sedimented layer from the rest of the pulp;

Description

METHOD FOR SEPARATING A MIXTURE OF FINALLY DIVIDED MINERALS FIELD OF THE INVENTION This invention relates to a process for separating a mixture of finely divided minerals into their constituents. In particular, the invention relates to a method for effecting this separation by a novel selective flocculation technique, wherein a dispersed aqueous pulp containing the mineral mixture is pre-conditioned for selective flocculation with an anionic polymer, by addition of a fatty acid such as oleic acid, as a source of a polyvalent metal cation such as calcium chloride. The fatty acid and polyvalent metal cation selectively coat the component of the mixture which subsequently flocculates with the anionic polymer. Preferably, an anionic polymer salt dispersant is used in the process. The invention is especially adapted for the removal of color impurities from kaolin clay. BACKGROUND OF THE INVENTION When mineral ore particles or mixtures of sufficiently large powders, for example greater than 325 mesh (E.U.A.), the components of a mixture can be separated by simple physical means, such as magnetic separation or air. When the particles in the mixture are finer, a more sophisticated technique may be required to achieve efficient separations. It is conventional to make the separation of finely divided ore, for example particles finer than 325 mesh (US sieve) by forming a mixture in an aqueous pulp and adding chemicals that achieve the desired separation. A widely used procedure is light foam flotation. In the case of light foam flotation of phosphate minerals or oxidized from siliceous gangue, it is conventional to use an acid collector and a salt promoter. The coated mineral particles are separated from the gangue collector in the form of a light foam. Frequently a light foam and aeration separating apparatus is employed. When light foam flotation is applied to extremely fine-grained minerals (sludge) such as certain kaolin clays, the light foam flotation of the colored impurities in the clay using the fatty acid collector becomes more difficult and it is necessary to use a clay dispersant to keep clay particles dispersed during the light foam flotation process. A seminal event in the benefit of flotation of minerals formed in sludge, especially in the flotation of titanium impurities of kaolin of fine particle size, is described in US Pat. No. 2,990,958 to Green et al. This procedure is often referred to in technical terms as ultraflotation. Ultra flotation has been practiced on a vast scale for several decades to improve kaolin clays. The process has been extended to the benefit of other commercially valuable minerals such as cassiterite (tin oxide), phosphate sludge, fluorite minerals or other non-sulfur minerals. Another flotation process of commercial kaolin, referred to as TRT, employs calcium chloride and oleic acid. See Patent of the U.S.A. No. 4,472,271 to Bacon et al. In the case of kaolin clays containing significant amounts of sludge, conventional light foam flotation techniques may not produce the desired separation of color bodies. The so-called "selective flocculation" is another procedure that is widely used in commerce to separate finely divided minerals and powders. In the case of clay, some procedures use anionic polymers to selectively flocculate the clay, leaving the impurities dispersed and susceptible to subsequent separation. Selective flocculating commercial variants employ weakly anionic polymer such as hydrolyzed polyacrylamide to selectively flocculate impurities in the clay, leaving the purified clay dispersed. See, for example, U.S. Pat. No. 3,837,482 to Sheridan, U.S. Pat. Nos. 3,701,147 and 3,862,027 both from Mercade, U.S. Pat. No. 3,371,988 to Maynard et al. And U.S. Pat. No. 4,604,369 (Shi). Previously in the history of light foam flotation it was proposed to add a cationic polymeric flocculating agent to a mineral pulp already conditioned with a fatty acid collector. This was followed by flotation of light foam to achieve separation. See U.S. Pat. No. 3,138,550 of Woolery. To achieve selective absorption of a flocculating agent in a particular component of a mixture, a number of methods have been suggested in the literature [Yu and Attia; in "Flocculation in Biotechnology and Separation Systems," (Flocculation in Separation Systems and Biotechnology) (Y.A. Attia, ed), p. 601, Elsevier, Amsterdam, 1987; Behl, S. and Moudgil, B.M., Minerals and Metallursical Processing. (Metallurgical Processing and Minerals) 5, 92, 1992 and Behl, S. and Moudgil, B.M., Journal of Colloid Interfase Science (Journal of Colloid Insect Science), 160, 1993]. One method involves selectively blocking the active sites in the inert and non-flocculent component for absorption of the polymeric agent. This can be achieved by absorption of a fraction of the lower molecular weight of the flocculating agent, which can act as a dispersant and / or site blocking agent before exposing the particle surfaces to the flocculating agent. Both floating light cq foam or selective flocculation have limitations, especially dua? Dp are applied to ores formed in sludge. In the case of float of light kaolin clay foam where a significant portion of the material is in the range of submicron sizes, even the ULTRAFI TRATION can not achieve adequate separation of the color bodies in kaolinite at a commercially viable level with an acceptable recovery of purified kaolin. Similar difficulties are experienced when TREP is used to benefit this ultra-fine clay on a commercial scale. On the other hand, selective flocculation processes using anionic polymers generally result in flocs that are too slow to settle unless copious amounts of salt are used to facilitate settling of the flocs. This requires multiple and expensive washing steps, because the presence of the salt with the clay will adversely affect the rheology of the clay. CQMPENDIQ PE THE INVENTION We have invented a novel process for separating finely divided solids mixtures which represents a significant separation of the known light foam selective flotation and flocculation processes. Our process overcomes many of the deficiencies of the selective foam flocculation and light foam flotation processes of the prior art and provides means to produce novel kaolin pigment products when applied to kaolin acid. The process uses selective flocculation of constituents in a previously dispersed aqueous mineral pulp, preferably a pulp dispersed with sodium metasiliphate and sodium polyacrylate. The pulp is dispersed in the sense that the particles do not aggregate with each other. The dispersed pulp is preconditioned for subsequent selective flocculation by the addition of both a fatty acid and a water soluble source of a polyvalent metal cation. The amounts of fatty acid and polyvalent metal cation are insufficient to flocculate components in the dispersed pulp. When cationic polymer is added to the preconditioned dispersed pulp, a dense flocculated phase forms virtually instantaneously and quickly settles as a gelatinous, viscous and dense bottom layer; the upper layer is a pulp of dispersed fluid containing the non-flocculated mineral particles. The flocculated phase also contains virtually all of the fatty acid and polyvalent oases introduced into the pulp. The separation of the dense lower gelatinous layer from the rest of the pulp is easily achieved by decanting or other conventional unit operation. In the process of this invention, the pulp is not subjected to light foam flotation after introduction of fatty acid and polymer as with oolery (top); no light foam flotation is employed to achieve the separation of the lower flocculated phase from the upper dispersed phase. In an especially preferred embodiment, the invention is practiced with impure kaolin clay containing discrete particles of at least one colored titanium impurities and kaolin and the impurities are so fine that they do not respond satisfactorily to conventional light foam flotation processes such as Ultra flotation or TREP. The dispersant used to purify these kaolins according to the present invention is preferably sodium metasilicate supplemented with sodium polyacrylate. Examples of these ultra-fine kaolin are those extracted in East Georgia, E.U.A.; these clays having average particle sizes below 0.5 miera, and currently benefit by selective flocculation using a weakly anionic polymer, followed by addition of copious amounts of salt to facilitate floc sedimentation and multiple washing steps. We consider that the invention constitutes an important and significant discovery in the benefit of a multitude of finely divided mineral mixtures that can provide a significant economic benefit over the technologies currently practiced. For example, high gloss kaolin products (90% GE brightness and above) can be made without light foam flotation. In some cases, high gloss kaolin products can be produced without conventional back processes intended to increase gloss, such as for example, leaching and magnetic separation. This is explained by the fact that our process can achieve this significant reduction in the amount of carbon impurities that conventional downstream benefit operations may not require to generate kaolin products of desired brilliance. In some cases, preliminary grain separation (necessary in most kaolin benefit schemes) can be omitted because the granules can be removed in the layer of flocculated impurities sedimented. The process of the invention does not introduce the undesirable soluble salts introduced during the selective flocculation processes of the prior art. This can provide significant cost reduction in kaolin processing because multiple washing steps are not required. In fact, the multivalent metal cations present in the kaolin crude or introduced during processing can be collected substantially quantitatively in the flocculated layer, in this way without deteriorating the rheology of the purified kaolin. Benefited kaolin products that have remarkable, good rheology can occur. DESCRIPTION OF PREFERRED MODALITIES The process is capable of removing titanium oxide (rutile and anatase and its mixtures) from kaolin, even when titanium oxide and kaolin are in the form of very fine particles. The process is also capable of separating other minerals other than sulfur from other silicates. It can be used to separate certain sulfides containing iron such as pyrite. The process of this invention can be used to remove apatite (calcium phosphate) from silicate minerals in phosphate ores, ore concentrates and ore pre-concentrates, even when the feedstock is formed in sludge. The process can be used to concentrate caciterite formed in sludge (tin oxide) iron oxide, ollastonite, alkaline earths such as dolomite, silicate gangue magnesite cache in ores, ore concentrates and ore pre-concentrates. Zeolites of natural origin, which contain alkaline earth ions such as chabazite, can be separated from silicate gangue. Mineral specimens present in various silicate bargains are feldspar, smectite clay, fine silica, phosphate clays and kaolins. The silicate materials remain in the dispersed phase during these separations. The process of the invention can also be used to concentrate ores of hirmenite, nickel ores, anatase and bauxite. In general, any mineral that can be coated by a collector for selective light foam flotation by the combination of fatty acid and polyvalent cation promoter, can be separated as a gelatinous flocculated lower layer by the process of the invention. The process is useful for separating all minerals or a significant portion of which are finer than 325 mesh. (US Sieve). Granules that are defined as mesh particles plus 325 (US sieve) ie particles that are retained in a 325 mesh sieve, it can be removed from the feed before or during the process. The invention appears to have the most significant commercial value for separating ultra-fine minerals, for example mixtures of minerals, wherein at least 50% by weight of the particles are in the sub-micron size range. Application of the process to these finely mineralized mixtures represents the potential for the most significant cost reductions. This is explained by the fact that conventional expensive pre-or post-processing steps such as leaching and washing can be eliminated or carried out more quickly. The invention is described in detail for processing impure ultra-fine kaolin from East Georgia, E.U.A. Color impurities are predominantly titanium oxide (both rutile and anatase). The analysis of typical titanium oxide (Ti02) is in the range of 2.0 to 4.5% by weight, based on the dry weight of the clay detached from granules as it was extracted. However, acceptable improvements in brightness have been achieved with East Georgia clay crudes where Ti02 had analysis as low as 0.6% to one as high as 6.0%. A portion of the iron is typically located in the structural network of the kaolin crystals. Iron is present in smaller amount, for example up to 1.0% Fe202 based on the dry weight of the granular clay. These clays may have a deficient response to oxidative and reductive leachates and do not respond satisfactorily to known flotation schemes.

The particle size of Georgia East raw clays varies from 80% finer than two microns to in excess of 95% finer than two micras e.s.d. (e.s.d. = equivalent spherical diameter, equivalent spherical diameter). At least 50% by weight in general is finer than 0.4 miera e.s.d .. In this way, these clays fall within a common definition of ores formed in sludge as used in light foam flotation technology. The East Georgia clays are becoming of increasing importance to the paper industry due to the excellent high shear rheology as a carbonate-compatible co-pigment. The separation of impurities of titanium oxide improves the brilliance and the tone (less yellow of the clay), resulting in a more compatible carbonate co-pigment. The primary dispersant currently preferred in the practice of the invention is sodium metasilicate. We have found that compositions obtained by mixing sodium hydroxide with sodium silicate solutions such as NMR-brand sodium silicate in the same ratio as Na20 / SiO2 as sodium metasilicate, do not result in such extensive Ti02 removal from the kaolins of Georgia East as can be achieved using sodium metasilicate. The primary dispersant of sodium metasilicate can be added dry or as a solution in water. When added as a solution, the concentration of the metasilicate is not important. The primary dispersant is added to a clay from 5% to 70% solids, preferably over 50% solids using 1.36 to 4.08 kg (3 to 9 pounds) per ton, preferably over 2.62 kg (6 pounds) per ton , of sodium metasilicate, in dry weight based on dry clay weight. Sodium metasilicate in excessive amounts will tend to coagulate the suspension; this has an adverse effect on the selective flocculation process. When added insufficiently, the sludge will not disperse, this adversely affects the selective adsorption of the flocculating agent. A degree of water-soluble dispersant of sodium or ammonium polyacrylate such as sodium polyacrylate C-211, is advantageously added to the pulp previously dispersed with sodium metasilicate using .0454 to .363 Kg (.1 to .8 pounds) per ton based on the dry weight of the clay, in order to ensure dispersion of the clay through processing. Typical molecular weights of polyacrylate dispersants can be in the range from 2000 to 20,000. The acrylate dispersant is essential to achieve high recovery of a purified clay. Recommended viscosity of a suitably dispersed slurry for purposes of this invention is less than 600 CPS at 20 rpm as measured by a No. 12 spindle in a Broo field viscometer. The pH of a kaolin pulp before the addition of sodium metasilicate is usually in the range of 5 to 7. After addition of sodium metasilicate, the pH is usually in the range of 7 to 11; Sodium or ammonium polyacrylate usually has no effect on sludge pH. After addition of primary dispersant and acrylate salt (secondary dispersant) the dispersed kaolin pulp is a light fluid that has the appearance of a malted milk. When it is kept stationary essentially no stratification is carried out nor flocs appear. As mentioned, the sludge is dispersed in the sense that the particles are not added. The degree of dispersion may not be the same as that of a sludge dispersed at a minimum viscosity (ie, a rheological scattered sludge) Fatty acid used in the process to precondition the impure clay (or other feed material) for selective flocculation, may It is of the type conventionally used in the flotation of lightweight mineral oxide foam, for example fatty acids with 12 to 18 carbon atoms, currently referred to as oleic acid, mixtures of fatty acids and resins such as tallow oil and fatty acids. Fatty acids can be used The amount of fatty acid will vary with the content of impurities in the kaolin (or relative amount of non-silicate minerals in other minerals that can be coated with oleic acid and polyvalent cations) and typically is in the range of .454 to 4.54 Kg (1 to 10 pounds), more usually from 1.36 to 2.27 Kg (3 to 5 pounds) per ton, based on the weight of dry clay. When too much fatty acid is used, a film (or separate phase) is observed on the surface of the sludge; this film traps fine-colored aggregates, preventing them from settling after flocculation; when an insufficient amount of fatty acid is used, the separation efficiency of the process is more defective. Addition of light foam forming materials is not advantageous. A salt containing a polyvalent metal cation is added to the pulp simultaneously with or before the addition of the fatty acid. When treating a pre-concentrated ore or a concentrate containing a solid that provides polyvalent cations in pulp, it may not be necessary when adding any other source of polyvalent cations. Suitable salts containing polyvalent metal cations are soluble in water at the pH of the pulp to which the salt is added. Especially preferred are salts containing divalent metal cations, particularly calcium, magnesium and barium. Other polyvalent metal cations that may be employed include aluminum, ferric, tin, titanium, manganese and rare earths. When clay is processed, colorless cations such as calcium and magnesium are recommended. The preferred anion of the salt is chloride, although nitrate, sulfate, acetate or formate salts may be employed. The salt is added dry or as an aqueous solution; salt is added in the general amount in the range of approximately 0 to 1.82 Kg (0 to 4 pounds) / ton, preferably approximately 91 kg (2 pounds) per ton of dry clay. When excess salt is used, undesirable non-selective flocculation of the pulp may occur and this may interfere with the ability of the polymer to flocculate the titanium oxide selectively. Also, excess salt (with respect to fatty acid) may require one or more washing steps that can contribute significantly to the cost of processing. When salt is not added, the formed flocs are very small and this will adversely affect the separation process. The flocculating agent employed in the process is highly anionic and is a homopolymer or copolymer of the carboxylic acid, carboxylic anhydride or carboxylic acid salt monomer with a suitable nonionic monomer. Examples of nonionic monomers are carboxylic acid amides and carboxyl alkyl esters. A co-polymer of acrylic acid (or its salt) and acrylamide are preferred for kaolin processing. Since the polymer is highly anionic, it consists predominantly of the acrylic acid group. A flocculating agent successfully employed in the process is a highly cationic copolymer of high molecular weight of sodium acrylate and acrylamide having more than 50% (by weight) of acrylate and a molecular weight exceeding 5 million. The preferred polymer has 95% or more of acrylate acrylate (by weight) in the copolymer and a molecular weight in the range of 10 to 30 million with 25 million preferred **. Polymers employed in the accompanying examples were obtained from Sharpe Specialty Chemical Co. and include Sharpfloc ™ 9990, 9950, 9954, and 8581. The production method of these polymers is proprietary. In theory they can be prepared either by copolymerization of acrylamide and acrylic acid (anionic monomer) or by partial hydrolysis of polyacrylamide. Fatty acid and salt are usually added to a previously dispersed pulp of 10 to 50% solids. Minimal dilution occurs when these reagents are added, so that the solids in the pulp remain essentially unchanged. The pH of the sludge is typically in the range of 6.5 to 10 after addition of fatty acid and salt. Pulp solids after addition of fatty acid and salt, are generally in the range of 20 to 45 with about 40% preferred. It is convenient to dilute the pulp with water, preferably water having a low mineral content, after addition of fatty acid and salt but before adding the polymer. The polymer is added as a solution having a concentration (weight) of less than 0.5%. At higher concentration, the flocculated material may be added due to mixing limitations. At very low concentrations, the volume of water added becomes very large, thus causing handling problems. When constituting the polymer solution, water with a low content of calcium and magnesium should be used. The agitation should be sufficiently moderate to avoid degradation of the polymer while it is solubilized in water.

Virtually after the polymer solution is added to the well-dispersed pulp pre-conditioned with fatty acid and metal salt, the formation of flocs can be observed. It is not necessary to shake the contents of the container in order to form the floccule. However, the agitation, still severe, will not deteriorate the formation of floccules. Within a few short minutes of rest under resting or semi-resting conditions, the flock sediments as a well-defined viscous gelatinous layer that predominantly contains all the titaniferous minerals in the starting clay. In the case of Giorgia East kaolin, the iron content of the clay remains essentially unchanged. However, in the case of kaolins containing iron ore released, the iron should be concentrated in the flocs. Unless the clay has been stripped of grains before treatment, the granules will be reported in the flocculated layer when raw kaolin is processed. The lower sedimented layer is generally grayish-brown and distinctly darker than the dispersed top layer containing the purified clay. Most of the water in the pulp appears in the top layer rich in supernatant clay. After addition of polymer, a dispersion of beneficiated kaolin product fluid can be decanted into a cylindrical tank, column, etc., with the lower flow having the gelatinous mass containing coarse particles greater than 5 microns, impurities including colored bodies , and other minerals. Mechanical devices such as a lower half-shell or a low shear centrifugal device can also be used to separate the gelatinous flocs from the dispersed product. The downstream processing of decantation can provide numerous opportunities to optimize the total process yield and decrease the amount of residual impurities remaining in the dispersed phase. This will have an impact on the quality of the product benefited and the total cost to manufacture this product. Smaller (even colloidal) florets may remain in the suspension in the dispersed benefited kaolin product, due to the high viscosity imparted to the kaolin sludge by the addition of the flocculant air. These flocs are structures that contain impurities and fatty acid and are unable to settle after the initial polymer addition. These small flocs can be dispersed by the addition of an appropriate dispersant such as C-211 (sodium polyacrylate). An alternative method to deal with the small amount of floccules is to retain the small flocs in a sieve, when operating in a batch mode. Sealing of the screen can be a significant process problem when this type of process is operated in a continuous manner, without frequent washing of the screen surface with an agent capable of detaching the flocs. This agent can be water or a high pressure solvent. Further improvement in the purity, physical properties and brilliance of the beneficiated kaolin product can be achieved with an HGMS (high gradient magnetic separator) having a field strength above two teslas, preferably up to 5 teslas. Also, impurities located in the pore structure of the ore can be removed with a lid of the "grinding with debugging" process upstream of the HGMS. This unit operation does not subject the pulp to significant changes in particle size distribution. This process will provide a release of embedded impurities that are not removed by the initial implementation of the process of this invention. Additional brightness improvement can be achieved using a conventional reduction leachate. A dithionite chemical agent can be employed or the reagent can be formed in situ and is described in U.S.A. No. 5,145,814 issued to Willys et al. Leachate with oxidation can be of benefit when treating a clay contaminated with organic impurities. The process of the invention can be used to further reduce the level of color impurities in kaolin materials that have already been subjected to partial purification or media such as light foam flotation.In laboratory experiments, simple propulsion mixers can be used during all stages of processing. Batch or continuous operations can be used. In continuous operations, a clay cage mixer may be employed to mix the dispersed pulp after addition of fatty acid and salt. The following examples are given to illustrate the invention in the best currently preferred mode of operation and will not be considered as limiting the invention. In Examples 1 to 5, the kaolin crudes employed were from an amine extracted in East Georgia, E.U.A. The extrusion of typical particle size was 80% (weight) finer than two microns with an average particle size of 0.3 to 0.4 miera. All quantities are reported on a dry weight basis unless otherwise indicated. All mesh sizes refer to values obtained using screens from the U.S. EXAMPLE 1 According to the invention, Eastern Georgia kaolin crude was mixed for ceramics at 60% solids with 3.18 Kg (7 pounds) / ton of anhydrous sodium metasilicate and .27 Kg (.6 pound) / tonne of C-211 (sodium polyacrylate) using a Co-mixer. This sludge is mixed for 15 minutes to ensure complete formulation of the raw clay, the sludge is sieved through a 325 mesh sieve to remove the coarse granule material. The resulting sludge is then diluted to 40% solids. The mud pH was 10.4. To this slurry, 2.27 Kg (5 pounds) / tonne of oleic acid and .91 Kg (2 pounds) / tonne in calcium chloride solution (38.5%) were added simultaneously while mixing the sludge. The resulting slurry was mixed thoroughly at room temperature for 15 minutes. To this slurry, add .114 Kg (.25 pound) / ton of Sharpfloc polymer * * 9950 with slight agitation Sharpfloc ™ 9950 is a polyacrylamide and polyacrylate co-polymer with 95% anionic loading and molecular weight exceeding 10%. The required amount of polymer is diluted to such a concentration that when added to the clay sludge, the resulting solids loading is 20% .Color flocs began to appear immediately.As soon as agitation was stopped, the flocs The floccules settled for 30 minutes.The floccula phase (gelatinous gray-brown phase) constitutes approximately 30% of the volume of the sludge.The dispersed slime is decanted to separate it from the flocculated layer and passes through of a 325 mesh sieve to remove any small flocs still remaining with the purified kaolin sludge.The solids content of the settled sludge was 10% .The sludge was then flocculated, using alum and sulfuric acid, and filtered in a Buchner funnel. The filter cake was dried in a microwave oven.

The results, reported in table 1, show that the Ti02 level of East Georgia kaolin is reduced from approximately 4% to approximately .6%. The bright GE improved from 80.0% to 90.4% and an outstanding clay recovery of 73%. EXAMPLE 2 A portion of the dispersed sludge used in Example 1 was conditioned with oleic acid and calcium chloride as in Example 1. This sludge was aged for 12 hours. The sludge was then diluted to 20% solids and subsequently .114 kg (.25 lb.) / ton of Sharpfloc ™ 9950 polymer at 0.01% (concentration by weight) are added with slight agitation. Color flocs begin to appear and once the agitation stops, the flocs settle very quickly. The flocs were pelleted for 30 minutes and formed a lower layer constituting approximately 30% by volume of the sludge. The scattered sludge is decanted and passes through a 325 mesh screen to remove any small flocs still remaining with the purified sludge. The product had a GE brilliance of 89.0% recovery of kaolin in the process was 82%. EXAMPLE 2A The purified mud of the example 2 is treated with 2.27 kg (5 pounds) / ton of reduction leach (sodium diotinite) floc with 2.72 kg (6 pounds) / ton of alum and sulfuric acid (pH 3.5) and filtered. These steps were carried out to determine if the clay could be further brightened by conventional reductive leachate. The leached sample is dried and the results are reported in table 1. data in the table show that the GE brightness of the leached product was 89.9%. This indicates that the East Georgia oil beneficiary responded only moderately to the reductive leachate. EFFECT OF PR ESQ OF THE INVENTION AND SEPARATION PE IMPURITIES OF THE CAOLÍN DE GEORGIA THIS TABLE i GEB Ti02 /% Fe203,% Recovery by weight in weight% by weight of clay * CRUDO DESPROVISTO DE GRANULOS 80.0 3.94 0.92 Example 1 90.4 0.64 0.92 73 Example 2 89.0 - - 82.0 Example 2a 89.9 * Based on the weight of crude oil devoid of granules. EXAMPLE 3 A test was conducted to study the effect of lower molecular weight of flocculant in the selective flocculation process of the invention. The approximate average molecular weight of the polymer used in this example is specified by the supplier is 5MM.

Georgia East crude was blended to 60% solid ceramics with 3.18 kg (7 pounds) / ton of anhydrous sodium metasilicate and .227 kg (.5 lb) / ton of C-211 (sodium polyacrylate) using a mixer Cowles. This mud is mixed for 15 minutes to ensure complete constitution of the raw clay. This sludge was passed through a 200 mesh screen to remove the coarse granule material. Previous examples a 325 mesh screen was employed. A much thicker sieve was used in this example due to the ease of sifting the sludge through a 200 mesh screen. The resulting sludge is then diluted to 40% solid. The mud pH was 10.5. To this sludge are added 1.33 Kg (3 pounds) / ton of oleic acid and .91 Kg (2 pounds) / ton of calcium chloride solution (.91 Kg (2 pounds) / ton expressed on a dry weight basis) simultaneously while the mud is mixed. The resulting slurry was thoroughly mixed for 3 minutes and diluted to 30% solid. To this slurry, .136 Kg (.30 pound) / ton of Sharpfloc "* 9954 under is added slight agitation.The required amount of polymer, before addition is diluted to a concentration such that when it is added to the clay sludge, the The resulting solids charge is 20% Gray-brown flocs began to appear immediately As soon as agitation was stopped, the flocs sedimented The flocs were very small compared to those observed in examples 1 and 2. Decanted mud was dried in the oven and analyzed.

Chemical analysis of the beneficiated sludge showed that the Ti02 level of East Georgia kaolin is reduced to approximately 4% to approximately 1.54%. The GE brightness improved from 80.0% to 87.2% and the recovery of purified kaolin was 61%. EXAMPLE 4 This test was performed to study the effects of another polymer in the selective flocculation process. The polymer employed was supplied by Sharpe Specialty Chemical Co. as SharpfloCtH 8581. This is a copolymer of acrylamide and 2-acrylamide-2-methyl, propyl sulfonic acid, sodium salt (poly AMPS). This polymer is 58% by weight (of anionic monomer in the copolymer) The approximate molecular weight of the polymer as specified by the supplier is 15MM EXAMPLE 3 was repeated with Sharpfloc ™ 8581 as the flocculant. To appear almost as soon as the flocculant is added.After the agitation stops, the floccules settled very quickly.The flocs were very large.The flocs were baked and analyzed.The results show that the Ti02 level of the kaolin from Georgia East is reduced to approximately 4% to approximately .92% .The GE brightness improved from 80.0% to 89.4% and the recovery was 45% EXAMPLE 5 The test was conducted to study the effect on different salts in the process of selective flocculation of the invention The salts used were calcium chloride, calcium sulfate, sodium chloride and ammonium chloride Example 3 was repeated with the different salts As mentioned above, Sharpfloc ™ 9950 is used as the flocculant. Gray-brown flocs begin to appear almost as soon as the flocculant is added in case of calcium salts. Once the agitation stops, the flocs sediment very quickly. The flocs were baked and analyzed. The results are illustrated in Table 2. The results show that no separation was observed with a salt of a monovalent cation. EXAMPLE 6 f Dolomite-Silicate Separation This example illustrates the separation of silicate gangue dolomite using the process of this invention. A 1: 1 mixture of fine dolomite (-400 mesh) and East Georgia kaolin crude was mixed for ceramics at 60% solids with 3.18 kg (7 pounds) / ton of anhydrous sodium metasilicate and .227 kg (.5 pound) / ton of sodium polyacrylate C-211 using a Coles mixer. Kaolin is added to simulated silicate gangue associated with dolomitic ores. This mud is mixed for 15 minutes to ensure complete formulation of the raw clay. This sludge is passed through a 200 mesh screen to remove the coarse granule material (associated with the kaolin oil). The resulting sludge was then diluted to 40% solids, mud pH was 10.5. To this sludge are added simultaneously 1.36 kg (3 lbs) / ton of oleic acid and .91 kg (2 lbs) / ton of calcium chloride solution (.91 kg (2 lbs) ton (dry) while mixing the The resulting sludge is completely formulated for 15 minutes and diluted to 30% solids.To this sludge is added with slight agitation .136 Kg (.30 lbs) / ton of Sharpfloc polymer ** 9950. The required amount of polymer it is diluted to such a concentration that when added to the clay / dolomite mud, the resulting solids loading would be 20%, yellow florets begin to appear virtually immediately, as soon as the agitation stops, the flocs they settle quickly, the floccules settled for 60 minutes; The flocculated phase (yellow phase) that formed constitutes approximately 18% of the volume of the sludge. The flocs constitute approximately 60% of the total weight. The flocules were baked and analyzed. Dolomite content (measured by the concentration Mg of the flocs was 83%. EXAMPLE 7 This example demonstrates an embodiment of the invention wherein a source of polyvalent cations, such as calcium ions, is not added when a basafp mineral is purified in a divalent metal. Dolomite in an alkaline solution is expected to be a source of divalent cations, by virtue of its limited solubility (calcium and magnesium ions). Example 6 was repeated without calcium chloride added to the system. Upon addition of the flocculating agent, yellow flocs began to appear as a lower layer, once the agitation stopped. The flocs sedimented quickly. As expected, the flocs were smaller than those of example 6. The flocs were pelleted for 60 minutes; the floccular phase (yellow phase) formed approximately 9% by volume of the sludge. The flocs constituted approximately 50% by total weight. The flocs were baked and analyzed. It was found that the dolomite content of the flocs (measured by Mg concentration) was 67%. A result comparison of Examples 6 and 7 indicates that better selectivity in the presence of salt was observed. EXAMPLE 8 This example illustrates the separation of apatite from the silicate gangue. Example 3 was repeated (using a 1: 1 mixture of fine apatite) finer than 400 mesh) and crude kaolin from East Georgia. Upon addition of the polymeric flocculating agent, light yellow flocs began to appear; Again, the agitation stopped and the flocs settled very quickly. The flocs were sedimented for 60 minutes and the floccular phase (light yellow color phase) formed approximately 20% by volume of the sludge. The flocs constituted 60% by total weight. The flocs were baked and analyzed. The content of apatite (measured by the concentration of P205) of the flocs was 83%. EXAMPLE 9 This example illustrates the process application of the invention to the concentration of anatase titanium oxide from silicate gangue. Example 3 was repeated with a sample of Brazilian anastase ore. Upon the addition of the polymeric flocculating agent, dark brown flocs began to appear and once the agitation stopped, the flocs sedimented very quickly. The flocs sedimented for 60 minutes and the flocculum phase (dark brown phase) formed approximately 12% by volume of the sludge. The flocs constituted 50% of the total weight. Flocs and scattered mud were baked and analyzed. It was found that Ti02 was improved from 53% (in the anatase ore) to 65% with a recovery of 65%. The concentration of Ti02 in the dispersed phase was 4%. The material with granule content (mesh + 200, E.U.A.) in the ore was 30%.

TABLE 2; EFFECT OF TYPE OF SALT IN SELECTIVE FLOCKING Salt used Ti02% GEB Recovery for weight% of kaolin separation Brilliance purified% by weight * Calcium chloride 0. .60 91.0 44 Calcium sulphate 2. .77 83.8 80 Ammonium Chloride 3. .35 83.0 64 Sodium Chloride 3, .17 83.0 82 FOOD 3 .54 81.8 * based on the weight of crude oil depleted of granules.

Claims (21)

1. CLAIMS 1. A method for the selective separation of finely divided mineral particles in a mixture of mineral particles, comprising: (a) fog the mixture in a dispersed aqueous pulp; (b) adding to the dispersed aqueous pulp, a fatty acid and a source of polyvalent cations, unless at least one of the minerals in the pulp provides source polyvalent cations, without flocculating the pulp; (c) without adding a light foaming agent to the pulp, incorporating a high molecular weight organic anionic polymer, thereby fog flocs that sediment as a dense bottom layer; (e) and separate the sedimented layer from the rest of the pulp.
2. 2. The process according to claim 1, wherein the mineral that is flocculated is selected from the group consisting of metal oxide, alkaline earth carbonate, alkaline earth phosphate, zeolite and bauxite, and the mineral that remains dispersed is a silicate.
3. 3. The process according to claim 2, wherein the silicate mineral is kaolin clay and the mineral that is flocculated comprises colored titanium oxide.
4. 4. The process according to claim 1, wherein at least 50% of the mineral particles in the pulp are in the range of sub-sizes.
5. 5. - The process according to claim 1, wherein the dispersant in step (a) is sodium metasilicate.
6. 6. The process according to claim 5, wherein the sodium polyacrylate dispersant is also added in step (a).
7. 7. The process according to claim 1, wherein the sodium polyacrylate dispersant is added to the sedimented layer of step (d) and after which more polymer is added.
8. 8. The process according to claim 1, wherein sodium polyacrylate dispersant is added to the dispersed pulp of step (d).
9. 9. The process according to claim 1, wherein the fatty acid is oleic acid.
10. 10. The process according to claim 1, wherein the polyvalent metal salt is calcium chloride.
11. 11. The process according to claim 1, wherein the pulp is diluted after step (b) and before step (c).
12. 12. The process according to claim 1, wherein the polymer is highly anionic polyacrylamide or a copolymer of acrylamide.
13. 13. - The method according to claim 12, wherein the molecular weight of the polymer weight exceeds 5 million.
14. 14. The process according to claim 12, wherein the silicate mineral is kaolin clay, the metal oxide mineral comprises titanium oxide, the dispersant comprises sodium metasilicate and sodium polyacrylate, the fatty acid is oleic, in the polyvalent metal salt is calcium chloride and the anionic polymer is polyacrylamide.
15. 15. The process according to claim 14, wherein sodium metasilicate is used in an amount of about 2.27 to 4.54 Kg (5 to 10 pounds) / ton, sodium acrylate is employed in an amount at about .227 at .454 Kg (.5 to 1.0 pounds) / ton, oleic acid is used in an amount of approximately .91 to 3.6 Kg (2 to 8 pounds) / ton, calcium chloride is used in an amount of approximately .454 to 2.27 Kg (5 pounds) / ton and the anionic polymer is used in an amount of approximately .0454 to .454 Kg (.1 to 1 pound) / ton.
16. 16. The process according to claim 14, wherein the pulp in step (a) is at about 60% solids and is diluted before step (a) to about 40% solid and further diluted before from step (c) to about 20% solids.
17. 17. The process according to claim 2, wherein the alkali carbonate mineral is selected from the group consisting of calcium carbonate, magnesium carbonate and magnesium / calcium carbonate and the silicate mineral comprises clay.
18. 18. The process according to claim 2, wherein the phosphate mineral is apatite and the silicate mineral comprises clay.
19. 19.- A method for selective separation of finely divided mineral particles from a kaolin crude oil. This finely mineralized East Georgia contains particles of a colored titanium oxide impurity, comprising: (a) forming the raw clay in an aqueous dispersed pulp by adding sodium metasilicate and sodium polyacrylate; (b) adding oleic acid and calcium chloride to the dispersed pulp without flocculating the pulp; (c) without adding a light foaming agent to the pulp, incorporating an anionic polyacrylamide of high charge density, thus forming flocs that sediment as a dense lower gelatinous layer; (d) and separates the sedimented layer from the rest of the pulp which is a dispersion of purified kaolin.
20. 20. The process according to claim 18, wherein the metasilicate dispersant is added to the sedimented layer of step (d) after which additional polymer is added.
21. 21. The process according to claim 18, wherein the sodium polyacrylate dispersant is added to the purified kaolin dispersion of step (d).