Vanadium oxide extraction from Bayer process

Abstract

The invention relates to a method for improving the extraction rate of vanadium oxide in waste liquid generated by recovering aluminum oxide from bauxite through a Bayer process by using a water-soluble polymer.

Description

Technical Field

[0001] The present invention relates to a method for increasing the extraction rate of vanadium oxide from the waste liquid generated in the recovery of alumina from bauxite by the Bayer process. Background Art

[0002] The Bayer process is almost universally used for the production of alumina from bauxite. The method includes crushing bauxite ore, making it into a slurry in a caustic soda solution, and digesting it at high temperature and pressure. The caustic soda solution dissolves aluminum oxide to form an aqueous solution of sodium aluminate. Then, the components insoluble in caustic soda in the bauxite (referred to as "red mud") are separated from the aqueous phase containing the dissolved sodium aluminate. This separation is typically carried out by sedimentation (usually assisted by a flocculant) and filtration. After separation, trihydrate alumina precipitates from the sodium hydroxide aqueous solution and is collected as a product.

[0003] During this precipitation process, the clarified sodium aluminate solution is cooled and seeded with trihydrate alumina crystals to induce precipitation of alumina in the form of trihydrate alumina Al(OH)3. Then, the trihydrate alumina particles or crystals are classified by particle size and separated from the concentrated caustic soda solution. A flocculant is used to assist this classification and separation process. The very fine trihydrate alumina particles are recovered as seeds, while the coarser particles are collected as products. The remaining liquid phase, referred to as "waste liquid", can be evaporated through a series of heat exchangers and then cooled in a series of flash tanks. The condensate formed in the heater is reused in the process, for example, as boiler feed water 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, so it is worth extracting.

[0004] An example of a separation technique is to cool the waste liquid in a decanter. The low temperature is beneficial to the crystallization of vanadium oxide and its decantation, so the underflow is rich in vanadium oxide crystals. Then, the underflow can be centrifuged to separate the vanadium oxide-poor waste liquid from the solid composed of crystalline vanadium oxide.

[0005] Vanadium oxide is an unwanted compound in the Bayer process, so it is not desired to accumulate in the system. However, on the other hand, the vanadium extracted in this way can be recovered as a metal and sold to various industries (alloy manufacturing, chemical reaction catalysts).

[0006] Therefore, it is necessary to increase the yield of vanadium extraction from the waste liquid generated in the recovery of alumina from bauxite by the Bayer process. Summary of the Invention

[0007] Surprisingly, the applicant has found that the use of a water-soluble polymer during the decantation of the waste liquid can increase the extraction rate of vanadium generated in the recovery of alumina from bauxite by the Bayer process.

[0008] Without being bound by any theory, the addition of a water-soluble polymer aids in the crystallization of vanadium oxide and its precipitation in the waste liquor.

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

[0010] - Sending the waste liquor SL to an evaporator to separate condensed water from caustic soda concentrate CSC,

[0011] - Optionally, transferring the CSC to a container V,

[0012] - Cooling and maintaining the temperature of the CSC at 20°C - 80°C,

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

[0014] - Recovering the vanadium oxide VO particles in the suspension S 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] The present invention also includes all possible combinations of the various disclosed embodiments, whether preferred or given by way of example. In addition, ranges of numerical values are indicated, and the endpoints form part of these ranges. The present disclosure also includes all combinations between the limits of these numerical ranges. For example, the numerical range "1 - 20, preferably 5 - 15" means that the ranges "1 - 5", "1 - 15", "5 - 20" and "15 - 20" as well as the values 1, 5, 15 and 20 are disclosed.

[0017] "Hydrophilic monomer" means a monomer having an octanol / water partition coefficient Kow less than or equal to 1, where the Kow partition coefficient is measured in a 1 / 1 volume ratio octanol / water mixture at 25°C and at a pH of 6 - 8.

[0018] "Hydrophobic monomer" means a monomer having an octanol / water partition coefficient Kow greater than 1, where the Kow partition coefficient is measured in a 1 / 1 volume ratio octanol / water mixture at 25°C and at a pH of 6 - 8.

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

[0020]

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

[0022] The evaporation step of SL, i.e., separating the condensed water from the caustic soda concentrate CSC, can be carried out by 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 wt% of the water is condensed during this evaporation step. In other words, compared with the water content of SL, the water content of CSC is reduced by 20 wt% - 80 wt%.

[0024] Optionally, the CSC at the outlet of the evaporator is transferred to a container V. The transfer can be carried out through a pipeline connected to the outlet of the evaporator, or the last heat exchanger of a heat exchanger or a series of heat exchangers, and the device for filling the container.

[0025] Optionally, the CSC can be stirred in the 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. The cooling of the CSC can be carried out during the evaporation step, and / or during the transfer of the CSC from the evaporator outlet and the optional container V, and / or in the optional container V. In the absence of container V, the cooling of the CSC can also be carried out during the transfer of the CSC from the evaporator to the solid / liquid separation step and before adding the water-soluble polymer P.

[0027] The temperature control of the CSC is advantageously carried out by a temperature probe placed inside the CSC.

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

[0029] When the CSC is cooled during the transfer of the CSC to the 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 is maintained at 20°C - 80°C in the container V. The CSC can also be cooled at a temperature higher than 80°C during the transfer, and the CSC in the container V is 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 (divanadium trioxide or vanadium trioxide) V2O3; vanadium(IV) oxide (vanadium dioxide) VO2; vanadium(V) oxide (pentavanadium pentoxide) V2O5; vanadium oxide of the general formula V n O 2n+1 of (V3O7, V4O9 and V6O 13 ); vanadium oxide of the general formula V n O 2n-1 of (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 wt% of at least one vanadium oxide. The vanadium oxide VO particles obtained by the method of the present invention preferably contain at least 10 wt% 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 expression "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] A water-soluble polymer refers to a polymer that, when stirred at 25 °C and dissolved in deionized water at a concentration of 10 g.L-1, gives an aqueous solution free of insoluble particles.

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

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

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

[0038] - Non-ionic monomers: acrylonitrile, acrylamide, methacrylamide, N-vinylformamide (NVF), N-vinylacetamide, N-vinylpyrrolidone (NVP), N-vinylimidazole, N-vinylsuccinimide, acryloylmorpholine (ACMO), glycidyl methacrylate, glycerol methacrylate, diacetone acrylamide, N-hydroxymethylacrylamide (NMA), (meth)acrylic acid hydroxyalkyl (C1-C3) esters, (meth)acrylic acid 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), vinylsulfonic acid, vinylphosphonic acid, methallylphosphonic acid, 2-methacryloyloxyethyl sulfonate, methacryloylpropyl sulfonate, acryloylpropyl sulfonate, allylphosphonic acid, styrenesulfonic acid, 2-acrylamido-2-methylpropanedisulfonic acid, their salts and mixtures thereof,

[0040] - Cationic monomers: diallyldialkylammonium salts such as diallyldimethylammonium chloride (DADMAC); acidified or quaternized salts of dialkylaminoalkylacrylamides; acidified or quaternary ammonium salts of dialkylaminoalkylmethacrylamides, for example methylacrylamidopropyltrimethylammonium chloride (MAPTAC), acrylamidopropyltrimethylammonium chloride (APTAC), acidified or quaternized salts of dialkylaminoalkyl acrylates, such as quaternized or salt-formed dimethylaminoethyl acrylate (ADAME), acidified or quaternary ammonium salts of dialkylaminoalkyl methacrylates, such as quaternized or salt-formed dimethylaminoethyl methacrylate (MADAME), and mixtures thereof, where the alkyl is C1-C3.

[0041] Optionally, the polymer P comprises at least one zwitterionic hydrophilic monomer selected from the following list: derivatives of dimethylaminoethyl acrylate 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, derivatives of dimethylaminoethyl methacrylate 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-(methacryloyloxy)ethyl](dimethylamino)acetate, derivatives of dimethylaminopropylacrylamide such as 2-((3-acrylamidopropyl)dimethylamino)ethane-1-sulfonate, 3-((3-acrylamidopropyl)dimethylamino)propane-1-sulfonate, 4-((3-acrylamidopropyl)dimethylamino)butane-1-sulfonate, [3-(acryloyloxy)propyl](dimethylamino)acetate, derivatives of dimethylaminopropylmethacrylamide such as 2-((3-methacrylamidopropyl)dimethylamino)ethane-1-sulfonate, 3-((3-methacrylamidopropyl)dimethylamino)propane-1-sulfonate, 4-((3-methacrylamidopropyl)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 list: the group consisting of (meth)acrylates having a C4-C30 alkyl, arylalkyl (C4-C30 alkyl, C4-C30 aryl), propoxylated, ethoxylated or ethoxylated and propoxylated chain; (meth)acrylamide derivatives having a propoxylated, ethoxylated, ethoxylated and propoxylated C1-C3 alkyl, arylalkyl (C4-C30 alkyl, C4-C30 aryl) or dialkyl (C4-C30 alkyl) chain; alkylarylsulfonates (C4-C30 alkyl, C4-C30 aryl), or mono- or disubstituted (meth)acrylamides having a C4-C30 alkyl, arylalkyl (C4-C30 alkyl, C4-C30 aryl), propoxylated, ethoxylated, or ethoxylated and propoxylated chain; (meth)acrylamide derivatives having a C4-C30 alkyl, propoxylated arylalkyl (C4-C30 alkyl, C4-C30 aryl), ethoxylated, ethoxylated and propoxylated, or C4-C30 dialkyl chain; alkylarylsulfonates (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, they are present in an amount such that the polymer P remains soluble in water.

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

[0045] According to the invention, the polymer P is advantageously linear or structured. A structured polymer means a non-linear polymer having side chains which, when the polymer is dissolved in water, form a strongly entangled state, resulting in a very high low-shear viscosity.

[0046] The polymer P according to the invention may further consist of:

[0047] - at least one structuring agent, which may be selected from the group consisting of polyethylenically unsaturated monomers (having at least two unsaturated functional groups), such as vinyl functional groups, in particular allyl functional groups, acrylic and epoxy functional groups, such as methylene bisacrylamide (MBA), triallylamine or tetraallylammonium chloride or 1,2-dihydroxyethylidene bis-(N-acrylamide), and / or

[0048] - at least one macroinitiator, such as polyperoxides, polyazides and polymerization agents, such as transfer agents, such as polymer-trapping (co)polymers and polyols, and / or

[0049] - at least one functionalized polysaccharide.

[0050] The structuring agent, the macroinitiator, and the 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%. According to a specific embodiment, it can be higher than or equal to 0.00001 wt% of the monomer content.

[0052] According to the present invention, the polymer P can have a linear, branched, star, comb, dendritic, or block structure. 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 ("nitroxide-mediated polymerization"), or the introduction of structural monomers, concentration.

[0053] In a specific embodiment, the polymer P according to the present invention can be a semi-synthetic and thus semi-natural polymer. In this case, the polymer can be synthesized by the complete or partial graft copolymerization of at least one monomer according to the present invention and at least one natural compound, which is preferably selected from polysaccharides and their derivatives and their modified forms (chemically modified). The polymerization is usually carried out by copolymerization or by grafting, but is not limited thereto. Those skilled in the art can refer to the general knowledge of semi-natural polymers.

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

[0055] The polymerization is usually radical polymerization. By radical polymerization, we include radical polymerization using UV, azo, redox, or thermal initiators, as well as controlled radical polymerization (CRP) techniques or matrix polymerization techniques.

[0056] The synthetic polymer P according to the present 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 present invention. The preferred modification is post-hydrolysis.

[0057] Post-hydrolysis consists of the reaction of a hydrolysable functional group (advantageously a non-ionic functional group, more preferably an amide or ester functional group) of the monomer unit with a hydrolyzing agent. The hydrolyzing reagent can be an enzyme, an ion exchange resin, an alkali metal, or a suitable acidic compound. Preferably, the hydrolyzing agent is a Bronsted base. When the polymer P contains monomer amide and / or ester units, the post-hydrolysis reaction produces carboxylate groups.

[0058] According to the present invention, the polymer P can be in liquid, gel or solid form. When the 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, the polymer P is in liquid form, and more preferably, the polymer P is in the form of an aqueous solution.

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

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

[0061] [η]=K Mα α

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

[0063] K represents an empirical constant.

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

[0065] α represents the Mark-Houwink coefficient.

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

[0067] 0.01 ppm - 10,000 ppm (by weight) of the polymer P is added to the CSC, preferably 0.1 ppm - 1,000 ppm, more preferably 1 ppm - 100 ppm. The polymer P is added to the CSC all at once or in multiple fractions.

[0068] During the addition of the polymer P, the CSC can be stirred. Preferably, the stirring is stopped at the end of the addition of the polymer P.

[0069] During the step of adding the polymer P to the CSC, the temperature of the CSC is maintained at 20°C - 80°C, preferably at 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 optional container V, and / or in the optional container V, and / or during the transfer of the CSC from the evaporator to the solid / liquid separation step. In all cases, during the step of adding the polymer P, the temperature of the CSC is maintained at 20°C - 80°C, preferably at 20°C - 60°C.

[0071] Before, during or after adding the polymer P to the CSC, a crystallization promoter can be advantageously added to the CSC. During the step of adding the crystallization promoter, the temperature of the CSC is maintained at 20°C - 80°C, preferably at 20°C - 60°C. The crystallization promoter can initiate the formation of particles in the CSC, and more particularly, the formation of vanadium oxide VO particles. Preferably, the crystallization promoter 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 significantly completed, the particles of 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] Through the following examples, the present invention and its advantages will become more obvious. Detailed Description

[0076] Examples

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

[0078] The experimental procedure is as follows:

[0079] 1) Appropriately collect the waste liquid (SL) (temperature is about 40°C) at the outlet of the heat exchanger, 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 from the polymer to be tested. Stir and add a certain volume of this solution (depending on the concentration of the polymer to be tested) to 1 L of SL. For the blank, no polymer is added.

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

[0082] 4) After 2 hours, two distinct phases are observed in the separatory funnel. Collect the bottom phase and filter it using a Büchner filtration system.

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

[0084] For proper polymer selection, various polymers of various chemical properties provided by SNF SA have been 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 - Polymers and vanadium oxide extraction

[0087] 1 ACM = acrylamide

[0088] 2 AA.Na = sodium acrylate

[0089] 3 DMAEA - Quat = dimethylaminoethyl acrylate methyl chloride quaternary ammonium

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

[0091] 5 DADMAC = diallyldimethylammonium chloride

[0092] In any case, the chemical properties of the polymers used can improve the recovery rate of vanadium oxide. Polymers based on polysaccharides (such as dextran) have better effects. Therefore, further tests were conducted using Polymer 1.

[0093] Dose selection of Polymer 1:

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

[0095] Dose (ppm) Recycled 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] The recovery rate of vanadium oxide increases with the increase in dextran concentration. In addition, during the test, it seems that the use of dextran can improve the kinetics of VO particle precipitation. In fact, more crystal formation was observed in the SL containing dextran and with larger sizes compared to the blank.

Claims

1. A method for extracting vanadium oxide from the waste liquid SL produced by the Bayer process, which comprises the following steps: - sending the waste liquid SL to an evaporator to separate condensed water from caustic soda concentrate CSC; - optionally, transferring the CSC to a container V; - cooling and maintaining the temperature of the CSC at 20°C - 80°C; - adding a water-soluble polymer P to the CSC to obtain a suspension S containing vanadium oxide VO particles; - recovering the vanadium oxide VO particles in the suspension S 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 dextran.

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

5. The method according to claim 4, wherein the water-soluble polymer P comprises at least one non-ionic and / or anionic and / or cationic hydrophilic monomer selected from the following list: - Non-ionic monomers: acrylonitrile, acrylamide, methacrylamide, N-vinylformamide (NVF), N-vinylacetamide, N-vinylpyrrolidone (NVP), N-vinylimidazole, N-vinylsuccinimide, acryloylmorpholine (ACMO), glycidyl methacrylate, glycerol methacrylate, diacetone acrylamide, (meth)acrylic acid hydroxyalkyl (C1-C3) esters, (meth)acrylic acid thioalkyl (C1-C3) esters, 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), vinylsulfonic acid, vinylphosphonic acid, methallylphosphonic acid, 2-methacryloyloxyethyl sulfonate, methacryloylpropyl sulfonate, acryloylpropyl sulfonate, allylphosphonic acid, styrenesulfonic acid, 2-acrylamido-2-methylpropanedisulfonic acid, their salts, and mixtures thereof; - Cationic monomers: diallyldialkylammonium salts such as diallyldimethylammonium chloride (DADMAC); acidified or quaternized salts of dialkylaminoalkylacrylamides; acidified or quaternary salts of dialkylaminoalkylmethacrylamides, such as methylacrylamide-propyltrimethylammonium chloride (MAPTAC), acrylamide-propyltrimethylammonium chloride (APTAC), acidified or quaternized salts of dialkylaminoalkyl acrylates, such as quaternized or salt-formed dimethylaminoethyl acrylate (ADAME), acidified or quaternized salts of dialkylaminoalkyl methacrylates, such as quaternized or salt-formed dimethylaminoethyl methacrylate (MADAME), and mixtures thereof, where the alkyl is C1-C3.

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

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

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

9. The method according to any one of the preceding claims, wherein the crystallization promoter 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 crystallization promoter.

10. The method according to claim 9, wherein the crystallization promoter is a metal salt.

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