Extracting vanadium oxide from the bayer process

Abstract

The invention relates to a method for increasing the extraction of vanadium oxides from spent liquor produced by the Bayer process for the recovery of alumina from bauxite using water-soluble polymers.

Description

Technical Field

[0001] This invention relates to a method for improving the extraction rate of vanadium oxides from wastewater generated during the Bayer process for recovering alumina from bauxite. Background Technology

[0002] The Bayer process is almost universally used to produce alumina from bauxite. The method involves crushing the bauxite ore, slurrying it in a caustic soda solution, and digesting it under high temperature and pressure. The caustic soda solution dissolves the alumina oxides to form an aqueous solution of sodium aluminate. The caustic soda-insoluble components of the bauxite (called "red mud") are then separated from the aqueous phase containing dissolved sodium aluminate. This separation is typically carried out by sedimentation (usually assisted by flocculants) and filtration. After separation, alumina trihydrate precipitates from the sodium hydroxide aqueous solution and is collected as a product.

[0003] In this precipitation process, a clarified sodium aluminate solution is cooled and inoculated with alumina trihydrate crystals to induce the precipitation of alumina in the form of Al(OH)3. The alumina trihydrate particles or crystals are then fractionated by particle size and separated from the concentrated caustic soda solution. A flocculant is used to assist in this fractionation and separation process. Very fine alumina trihydrate particles are recovered as seed crystals, while coarser particles are collected as product. The remaining liquid phase, referred to as "waste liquid," is evaporated through a series of heat exchangers and subsequently cooled in a series of flash tanks. The condensate formed in the heaters is reused in this process, for example, as boiler feedwater or for washing bauxite residues. The remaining caustic soda is washed and recycled back to the digestion step. In some cases, the remaining caustic soda contains a certain amount of vanadium oxide, which is therefore worth extracting.

[0004] One example of separation technology is cooling the waste liquid into a decanter. The low temperature favors the crystallization and decanting of vanadium oxide, thus the underflow is rich in vanadium oxide crystals. The underflow can then be centrifuged to separate the vanadium oxide-poor waste liquid from the solid composed of crystalline vanadium oxide.

[0005] Vanadium oxides are undesirable compounds in the Bayer process, so their accumulation in the system is undesirable. However, vanadium extracted in this way can be recycled as a metal and sold to various industries (alloy manufacturing, chemical reaction catalysts).

[0006] Therefore, it is necessary to increase the yield of vanadium extracted from the waste liquid generated during the Bayer process for recovering alumina from bauxite. Summary of the Invention

[0007] Surprisingly, the applicant discovered that using water-soluble polymers during the decantation of waste liquid can improve the vanadium extraction rate of the Bayer process for recovering alumina from bauxite.

[0008] Unbound by any theory, the addition of water-soluble polymers facilitates the crystallization of vanadium oxide and its precipitation in waste liquid.

[0009] More specifically, the present invention relates to a method for extracting vanadium oxide from waste liquid SL produced by the Bayer process, comprising the following steps:

[0010] - The waste liquid SL is sent to an evaporator to separate the condensate from the caustic soda concentrate CSC.

[0011] -Optionally, transfer the CSC to container V.

[0012] - Cool and maintain the temperature of the CSC at 20°C-80°C.

[0013] - Add water-soluble polymer P to the CSC to obtain a suspension S containing vanadium oxide VO particles.

[0014] - The vanadium oxide VO particles in the suspension S are recovered by a liquid-solid separation method.

[0015] According to the present invention, "X and / or Y" means "X", or "Y", or "X and Y".

[0016] This invention also includes all possible combinations of the various disclosed embodiments, whether preferred or given by way of example. Furthermore, ranges of numerical values ​​are indicated, with their endpoints forming part of these ranges. This disclosure also includes all combinations between the limits of these numerical ranges. For example, the numerical range “1-20, preferably 5-15” means that ranges “1-5”, “1-15”, “5-20”, and “15-20”, as well as values ​​1, 5, 15, and 20, are disclosed.

[0017] "Hydrophilic monomers" refer to monomers with an octanol / water partition coefficient Kow of less than or equal to 1. The Kow partition coefficient is determined at 25°C in an octanol / water mixture with a volume ratio of 1 / 1 at a pH of 6-8.

[0018] "Hydrophobic monomer" refers to a monomer with an octanol / water partition coefficient Kow greater than 1, wherein the Kow partition coefficient is determined at 25°C in an octanol / water mixture with a volume ratio of 1 / 1 at pH 6-8.

[0019] The octanol / water partition coefficient Kow represents the concentration ratio (g / L) of the monomer between the octanol phase and the aqueous phase. It is defined as follows:

[0020]

[0021] In the Bayer process, waste liquid SL is a caustic soda solution obtained after precipitation and recovery of alumina trihydrate particles.

[0022] The evaporation step in SL, which involves separating the condensate from the caustic soda concentrate (CSC), can be carried out via a heat exchanger or a series of heat exchangers. Therefore, the evaporator can consist of a heat exchanger or a series of heat exchangers.

[0023] Typically, 20-80% by weight of water condenses during this evaporation step. In other words, the water content of CSC is reduced by 20%-80% by weight compared to that of SL.

[0024] Optionally, the CSC at the evaporator outlet is transferred to the container V. This transfer can be made via piping connected to the outlet of the evaporator, or heat exchanger, or the last heat exchanger in a series of heat exchangers, and to the device filling the container.

[0025] Optionally, the CSC can be stirred in an optional container V. Stirring is preferably carried out by stirring blades.

[0026] The CSC is cooled and maintained at a temperature of 20°C–80°C, preferably 20°C–60°C. Cooling of the CSC can occur during the evaporation step, and / or during the transfer of the CSC from the evaporator outlet and optionally into container V, and / or in optional container V. In the absence of container V, cooling of the CSC can also occur during the transfer of the CSC from the evaporator to the solid / liquid separation step, and prior to the addition of the water-soluble polymer P.

[0027] The temperature control of the CSC is advantageously achieved through temperature probes placed inside the CSC.

[0028] Preferably, the heat transfer fluid circulating in an optional container V equipped with a double shell provides cooling and temperature regulation for the CSC.

[0029] When cooling the CSC during transfer to container V, the CSC can be cooled at a temperature of 20°C–80°C during the transfer, and then the temperature of the CSC in container V can be maintained at 20°C–80°C. Alternatively, the CSC can be cooled at a temperature above 80°C during the transfer, and the CSC in container V can be further cooled to reach a temperature of 20°C–80°C.

[0030] "Vanadium oxide VO" refers to vanadium(II) oxide (vanadium monoxide) VO; vanadium(III) oxide (vanadium trioxide or vanadium trioxide) V₂O₃; vanadium(IV) oxide (vanadium dioxide) VO₂; vanadium(V) oxide (vanadium pentoxide) V₂O₅; and general formula V n O 2n+1 Vanadium oxides (V3O7, V4O9 and V6O) 13 ); General formula V n O 2n-1 Vanadium oxide (V4O7, V5O9, V6O) 11 V7O13 and V8O 15 ); or V3O5, or a combination thereof.

[0031] "Vanadium oxide (VO) particles" refers to particles containing at least 5% by weight of at least one vanadium oxide. The vanadium oxide (VO) particles obtained according to the method of the present invention preferably contain at least 10% by weight of at least one vanadium oxide.

[0032] "Polymer" refers to a natural polymer or a chemically modified natural polymer or a synthetic homopolymer or copolymer prepared from at least two different monomers.

[0033] The term "polymer P" is used in the following description and corresponds to the water-soluble polymer P used in the method of the present invention.

[0034] Water-soluble polymers are polymers that, when stirred at 25°C and dissolved in deionized water at a concentration of 10 g·L⁻¹, yield an aqueous solution free of insoluble particles.

[0035] The water-soluble polymer P can be a natural polymer, a chemically modified natural polymer, a synthetic polymer, or a semi-synthetic (or semi-natural) polymer.

[0036] When polymer P is a natural polymer, it is preferably a polysaccharide, and more preferably a dextran.

[0037] Preferably, polymer P is a synthetic polymer, more preferably a synthetic polymer comprising at least one nonionic and / or anionic and / or cationic hydrophilic monomer selected from the following list:

[0038] -Nonionic monomers: Acrylonitrile, Acrylamide, Methacrylamide, N-vinylformamide (NVF), N-vinylacetamide, N-vinylpyrrolidone (NVP), N-vinylimidazolium, N-vinylsuccinimide, Acryloylmorpholine (ACMO), Glycidyl methacrylate, Glyceryl methacrylate, Diacetone acrylamide, N-hydroxymethylacrylamide (NMA), (meth)acrylate hydroxyalkyl (C1-C3) esters, (meth)acrylate thioalkyl (C1-C3) esters, and mixtures thereof.

[0039] - Anionic monomers: acrylic acid, methacrylic acid, itaconic acid, crotonic acid, maleic acid, fumaric acid, acrylamidoundecanoic acid, 3-acrylamido-3-methylbutyric acid, maleic anhydride, 2-acrylamido-2-methylpropanesulfonic acid (ATBS), vinyl sulfonic acid, vinyl phosphonic acid, methylallylphosphonic acid, 2-methylethyl methacrylate, methyl methacrylate, methyl acrylate, allylphosphonic acid, styrene sulfonic acid, 2-acrylamido-2-methylpropanedisulfonic acid, their salts and mixtures thereof.

[0040] -Catonic monomers: diallyl dialkylammonium salts, such as diallyl dimethylammonium chloride (DADMAC); acidified or quaternized salts of dialkylaminoalkylacrylamides; acidified or quaternized salts of dialkyl-aminoalkylmethylacrylamides, such as methacrylamidopropyltrimethylammonium chloride (MAPTAC), acrylamide-propyltrimethylammonium chloride (APTAC), acidified or quaternized salts of dialkylaminoalkyl acrylates, such as quaternized or salted dimethylaminoethyl acrylate (ADAME), acidified or quaternized salts of dialkylaminoalkyl methacrylates, such as quaternized or salted dimethylaminoethyl methacrylate (MADAME), and mixtures thereof, wherein the alkyl group is C1-C3.

[0041] Optionally, polymer P comprises at least one zwitterionic hydrophilic monomer selected from the following list: dimethylaminoethyl acrylate derivatives, such as 2-((2-(acryloyloxy)ethyl)dimethylamino)ethane-1-sulfonate, 3-((2-(acryloyloxy)ethyl)dimethylamino)propane-1-sulfonate, 4-((2-(acryloyloxy)ethyl)dimethylamino)butane-1-sulfonate, [2-(acryloyloxy)ethyl](dimethylamino)acetate, dimethylaminoethyl methacrylate derivatives, such as 2-((2-(methacryloyloxy)ethyl)dimethylamino)ethane-1-sulfonate, 3-((2-(methacryloyloxy)ethyl)dimethylamino)propane-1-sulfonate, 4-((2-(methacryloyloxy)ethyl)dimethylamino)butane-1-sulfonate, [2-( [3-(acryloyloxy)propyl](dimethylamino)acetate, dimethylaminopropylacrylamide derivatives, such as 2-((3-acryloamidopropyl)dimethylamino)ethane-1-sulfonate, 3-((3-acryloamidopropyl)dimethylamino)propane-1-sulfonate, 4-((3-acryloamidopropyl)dimethylamino)butane-1-sulfonate, [3-(acryloyloxy)propyl](dimethylamino)acetate, dimethylaminopropyl methacrylamide derivatives, such as 2-((3-methacryloamidopropyl)dimethylamino)ethane-1-sulfonate, 3-((3-methacryloamidopropyl)dimethylamino)propane-1-sulfonate, 4-((3-methacryloamidopropyl)dimethylamino)butane-1-sulfonate and [3-(methacryloyloxy)propyl](dimethylamino)acetate and mixtures thereof.

[0042] Optionally, the synthetic polymer P comprises at least one hydrophobic monomer selected from the following group: (meth)acrylates having C4-C30 alkyl, arylalkyl (C4-C30 alkyl, C4-C30 aryl), propoxylated, ethoxylated, or ethoxylated and propoxylated chains; (meth)acrylamide derivatives having propoxylated, ethoxylated, ethoxylated, and propoxylated C1-C3 alkyl, arylalkyl (C4-C30 alkyl, C4-C30 aryl) or dialkyl (C4-C30 alkyl) chains; alkyl aryl sulfonates (C4-C30 alkyl, C4-C30 alkyl, C4-C30 aryl) chains; C1-C3 alkyl, arylalkyl (C4-C30 alkyl, C4-C30 aryl) chains; C4-C30 alkyl sulfonates; C4-C30 alkyl, C4-C30 aryl alkyl, C4-C30 aryl alkyl, C4-C30 alkyl ... (Methacrylamide) having a C4-C30 alkyl, arylalkyl (C4-C30 alkyl, C4-C30 aryl), propoxylated, ethoxylated, or ethoxylated and propoxylated chain monosubstituted or disubstituted; (Methacrylamide) derivatives having a C4-C30 alkyl, propoxylated arylalkyl (C4-C30 alkyl, C4-C30 aryl), ethoxylated, ethoxylated and propoxylated, or C4-C30 dialkyl chain; alkyl aryl sulfonates (C4-C30 alkyl, C4-C30 aryl) and mixtures thereof.

[0043] The water-soluble polymer P advantageously contains less than 1 mol% of at least one hydrophobic monomer. It may be free of hydrophobic monomers. When the water-soluble polymer P according to the invention contains one or more hydrophobic monomers, their presence should be in an amount that keeps the polymer P soluble in water.

[0044] In one specific embodiment, polymer P is produced by the condensation of epihaloalcohol and dialkylamine (preferably epichlorohydrin and dimethylamine).

[0045] According to the invention, polymer P is advantageously linear or structured. A structured polymer is a nonlinear polymer with side chains that, when dissolved in water, form a strongly entangled state, resulting in a very high low-gradient viscosity.

[0046] The polymer P according to the present invention may further be composed of the following:

[0047] - At least one structuring agent, selected from the group consisting of: polyene unsaturated monomers (having at least two unsaturated functional groups), such as vinyl functional groups, particularly allyl functional groups, acrylic and epoxy functional groups, such as methylenebisacrylamide (MBA), triallylamine or tetraallyl ammonium chloride or 1,2-dihydroxyethylenebis-(N-acrylamide), and / or

[0048] - At least one macromolecular initiator, such as polyperoxides, polyazides, and polymerizing agents, such as transfer agents, such as polymer-capturing (co)polymers, and polyols, and / or

[0049] - At least one functionalized polysaccharide.

[0050] The structuring agent, macromolecular initiator, and functionalized polysaccharide are referred to as "branching / crosslinking agents".

[0051] The amount of branching / crosslinking agent in the monomer mixture is advantageously less than 4 wt% of the monomer content (by weight), more advantageously less than 1%, and even more advantageously less than 0.5%. Depending on the specific embodiment, it may be greater than or equal to 0.00001 wt% of the monomer content.

[0052] According to the present invention, polymer P may have linear, branched, star-shaped, comb-shaped, dendritic, or block structures. These structures can be obtained by selecting initiators, transfer agents, polymerization techniques, such as controlled radical polymerization called RAFT (reversible addition-fragmentation chain transfer), NMP ("nitro oxygen-mediated polymerization"), or the introduction and concentration of structural monomers.

[0053] In specific embodiments, the polymer P according to the invention can be a semi-synthetic and therefore a semi-natural polymer. In this case, the polymer can be synthesized by full or partial graft copolymerization of at least one monomer according to the invention and at least one natural compound, preferably selected from polysaccharides and their derivatives and their modified forms (chemical modifications). Polymerization is generally carried out by copolymerization or by grafting, but is not limited thereto. Those skilled in the art can refer to general knowledge of semi-natural polymers.

[0054] Synthesizing polymer P does not require the development of any polymerization method. In fact, it can be obtained using any polymerization technique well known to those skilled in the art. It can be obtained through solution polymerization, gel polymerization, precipitation polymerization, emulsion polymerization (aqueous or reverse), suspension polymerization, polymer reactive extrusion polymerization, water-in-water polymerization, or micellar polymerization.

[0055] Polymerization is typically free radical polymerization. Free radical polymerization includes free radical polymerization using UV, azo, redox, or thermal initiators, as well as controlled radical polymerization (CRP) or matrix polymerization techniques.

[0056] The synthetic polymer P according to the invention can be modified after being obtained by polymerization. This is called post-modification of the polymer. All known post-modifications can be applied to the polymer according to the invention. Preferred modification is post-hydrolysis.

[0057] The post-hydrolysis consists of the reaction of the hydrolyzable functional group (preferably a nonionic functional group, more preferably an amide or ester functional group) of the monomer unit with a hydrolyzing agent. This hydrolyzing agent can be an enzyme, an ion exchange resin, an alkali metal, or a suitable acidic compound. Preferably, the hydrolyzing agent is a Brønsted base. When polymer P contains the monomeric amide and / or ester monomeric ester units, the post-hydrolysis reaction produces a carboxylic acid ester group.

[0058] According to the present invention, polymer P can be in liquid, gel, or solid form. When polymer P is in solid form, its preparation method includes a drying step, such as spray drying, drum drying, radiation drying such as microwave drying, or fluidized bed drying. Preferably, polymer P is in liquid form, and more preferably, polymer P is in aqueous solution form.

[0059] The polymer P has an average molecular weight greater than 500 Daltons, preferably greater than 1000 Daltons. Preferably, the average molecular weight is 1000 Daltons to 40 million Daltons, more preferably 10,000 Daltons to 20 million Daltons, and even more preferably 100,000 Daltons to 20 million Daltons.

[0060] Molecular weight is advantageously determined by the intrinsic viscosity of the (co)polymer. Intrinsic viscosity can be measured by methods known to those skilled in the art and can be calculated from specific viscosity values ​​at different (co)polymer concentrations by plotting specific viscosity (specific viscosity value (y-axis) against concentration (x-axis) and extrapolating the curve to zero concentration). Intrinsic viscosity can be plotted on the y-axis or using the least squares method. The molecular weight can then be determined using the Mark-Houwink equation.

[0061] [η]=KM α

[0062] [η] represents the intrinsic viscosity of the (co)polymer as determined by solution viscosity measurement methods.

[0063] K represents an empirical constant.

[0064] M represents the molecular weight of the (co)polymer.

[0065] α represents the Mark-Hovink coefficient.

[0066] K and α depend on the specific (co)polymer-solvent system.

[0067] Add 0.01ppm to 10,000ppm (by weight) of polymer P to CSC, preferably 0.1ppm to 1,000ppm, more preferably 1ppm to 100ppm. Polymer P may be added to CSC in a single addition or in multiple additions at different rates.

[0068] The CSC may be stirred during the addition of polymer P. Preferably, stirring is stopped when the addition of polymer P is complete.

[0069] During the step of adding polymer P to CSC, the temperature of CSC is maintained at 20°C-80°C, preferably 20°C-60°C.

[0070] The water-soluble polymer P can be added to the CSC during the transfer of the CSC from the evaporator outlet and optionally into container V, and / or in optional container V, and / or during the transfer of the CSC from the evaporator to the solid / liquid separation step. In all cases, the temperature of the CSC is maintained at 20°C–80°C, preferably 20°C–60°C, during the step of adding polymer P.

[0071] A crystallizer can advantageously be added to the CSC before, during, or after the addition of polymer P to the CSC. During the step of adding the crystallizer, the temperature of the CSC is maintained between 20°C and 80°C, preferably between 20°C and 60°C. The crystallizer can initiate the formation of particles in the CSC, more particularly, the formation of vanadium oxide (VO) particles. Preferably, the crystallizer is a metal salt. More preferably, the metal salt is a lead salt.

[0072] When the formation of vanadium oxide (VO) particles in the CSC is clearly finished, the particles in the resulting suspension S are recovered by a liquid-solid separation method. The liquid-solid separation method can be filtration, centrifugation, or other methods well known to those skilled in the art.

[0073] Preferably, the vanadium oxide (VO) particles recovered from the suspension S are washed at least once with an aqueous solution. The washing step includes obtaining a suspension of the particles in the aqueous solution and liquid-solid separation.

[0074] Preferably, the vanadium oxide VO particles recovered from the suspension S contain at least 5 wt% vanadium oxide, more preferably at least 10 wt%.

[0075] The invention and its advantages will become more apparent through the following embodiments. Detailed Implementation

[0076] Example

[0077] The actual use involves waste liquid (SL) from an alumina plant (Bayer process). The exact composition of the process waste liquid is unknown.

[0078] The experimental procedure is as follows:

[0079] 1) Collect waste liquid (SL) appropriately at the outlet of the heat exchanger (at a temperature of about 40°C) and use it quickly after sampling to limit the cooling of the solution.

[0080] 2) Prepare an aqueous solution containing 5 g / L of solid polymer for testing. Add a certain volume of this solution (depending on the concentration of the polymer being tested) to 1 L of SL while stirring. For the blank, do not add any polymer.

[0081] 3) Then, SL with or without polymer is introduced into a 1-liter separatory funnel (used to simulate a large industrial conical tank in the laboratory) and kept at room temperature for 2 hours.

[0082] 4) Two hours later, two distinct phases were observed in the separatory funnel. The bottom phase was collected and filtered using a Büchner filtration system.

[0083] 5) Then, the percentage of vanadium contained in the bottom phase is determined.

[0084] To facilitate appropriate polymer selection, various polymers with diverse chemical properties provided by SNF SA were tested at a concentration of 3 ppm (representing 0.6 mL of a 5 g / L aqueous polymer solution) (Table 1):

[0085]

[0086] Table 1 - Polymer and Vanadium Oxide Extraction

[0087] 1 ACM = Acrylamide

[0088] 2 AA.Na = Sodium acrylate

[0089] 3 DMAEA-Quat = methylchloroquaternized dimethylaminoethyl acrylate

[0090] 4 ATBS = 2-Acrylamide-2-methylpropanesulfonic acid

[0091] 5 DADMAC = diallyl dimethylammonium chloride

[0092] Regardless, the chemical properties of the polymer used can improve the recovery rate of vanadium oxide. The effect is even better based on the chemical properties of polysaccharides (such as dextran). Therefore, further tests were conducted using polymer 1.

[0093] Dosage selection for polymer 1:

[0094] Tests were conducted at different concentrations of polymer 1 (dextran) to obtain the optimal efficiency concentration (Table 2).

[0095] Dosage (ppm) Recovery mass (g) Vanadium oxide (%) 0 4.4804 18.0 0.5 5.1292 21.7 1 5.1545 21.9 1.5 5.2197 22.3 3 5.5215 22.2 4.5 7.1429 22.7

[0096] Table 2 - Polymer Dosage and Vanadium Oxide Extraction

[0097] Vanadium oxide recovery increased with increasing dextran concentration. Furthermore, during testing, the use of dextran appeared to enhance the kinetics of VO particle precipitation. Indeed, more crystal formation with larger sizes was observed in the SL containing dextran.

Claims

1. A method for extracting vanadium oxide from waste liquid SL generated from the Bayer process, comprising the following steps: - The waste liquid SL is sent to an evaporator to separate the condensate from the caustic soda concentrate CSC. -Optionally, transfer the CSC to container V. - Cool and maintain the temperature of the CSC at 20°C-80°C. - Add water-soluble polymer P to the CSC to obtain a suspension S containing vanadium oxide VO particles. - The vanadium oxide VO particles in the suspension S are recovered by a liquid-solid separation method.

2. The method according to claim 1, wherein the water-soluble polymer P is a polysaccharide.

3. The method according to claim 2, wherein the polysaccharide is a dextran.

4. The method according to claim 1, wherein the water-soluble polymer P is a synthetic polymer.

5. The method of claim 4, wherein the water-soluble polymer P comprises at least one nonionic and / or anionic and / or cationic hydrophilic monomer selected from the following list: -Nonionic monomers: Acrylonitrile, Acrylamide, Methacrylamide, N-vinylformamide (NVF), N-vinylacetamide, N-vinylpyrrolidone (NVP), N-vinylimidazolium, N-vinylsuccinimide, Acryloylmorpholine (ACMO), Glycidyl methacrylate, Glyceryl methacrylate, Diacetone acrylamide, Hydroxyalkyl (C1-C3) esters of (meth)acrylate, Thioalkyl (C1-C3) esters of (meth)acrylate, and mixtures thereof. - Anionic monomers: acrylic acid, methacrylic acid, itaconic acid, crotonic acid, maleic acid, fumaric acid, acrylamidoundecanoic acid, 3-acrylamido-3-methylbutyric acid, maleic anhydride, 2-acrylamido-2-methylpropanesulfonic acid (ATBS), vinyl sulfonic acid, vinyl phosphonic acid, methylallylphosphonic acid, 2-methylethyl methacrylate, methyl methacrylate, methyl acrylate, allylphosphonic acid, styrene sulfonic acid, 2-acrylamido-2-methylpropanedisulfonic acid, their salts and mixtures thereof. -Catonic monomers: diallyl dialkylammonium salts, acidified or quaternized salts of dialkylaminoalkylacrylamides, acidified or quaternized salts of dialkyl-aminoalkylmethylacrylamides, acidified or quaternized salts of dialkylaminoalkyl acrylates, acidified or quaternized salts of dialkylaminoalkyl methacrylates, and mixtures thereof, wherein the alkyl group is C1-C3.

6. The method according to claim 5, wherein the cationic monomer is selected from diallyl dimethyl ammonium chloride (DADMAC), methacrylamide-propyltrimethylammonium chloride (MAPTAC), acrylamide-propyltrimethylammonium chloride (APTAC), quaternized or salted dimethylaminoethyl acrylate (ADAME), quaternized or salted dimethylaminoethyl methacrylate (MADAME), and mixtures thereof.

7. The method according to any one of claims 1-6, wherein 0.01 ppm to 10,000 ppm of water-soluble polymer P is added to the CSC by weight.

8. The method according to any one of claims 1-6, wherein the vanadium oxide VO particles recovered from the suspension S are washed at least once with an aqueous solution.

9. The method according to any one of claims 1-6, wherein the CSC is transferred to the container V, and the CSC is cooled during the transfer of the CSC from the outlet of the evaporator to the container V.

10. The method according to any one of claims 1-6, wherein the crystallizer is added to the CSC before, during or after the step of adding the water-soluble polymer P, and the CSC is maintained at 20°C-80°C during the addition of the crystallizer.

11. The method of claim 10, wherein the crystallizing agent is a metal salt.

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