Method for enriching and separating titanium, vanadium and chromium from titanium white waste acid

Abstract

The invention provides a method for enriching and separating titanium, vanadium and chromium from titanium white waste acid, which comprises the following steps: mixing an alkaline substance containing calcium and / or magnesium with the titanium white waste acid to carry out acid-base neutralization reaction, reducing the acidity of the titanium white waste acid to precipitate titanium, vanadium and chromium, and carrying out reverse dissolution and precipitation by using sulfuric acid to obtain filtrate containing titanium, vanadium and chromium; freezing and filtering the filtrate containing titanium, vanadium and chromium to respectively obtain an aluminum ammonium sulfate crystal and the filtrate containing titanium, vanadium and chromium; then, the filtrate containing titanium, vanadium and chromium is diluted and hydrolyzed, the pH is adjusted, titanyl sulfate is hydrolyzed, sulfate of vanadium and chromium is not hydrolyzed, and metatitanic acid slurry and a diluted solution containing vanadium and chromium are obtained through separation; then neutralizing and filtering the vanadium-chromium-containing diluted solution to obtain a vanadium-chromium-containing filter cake; and then, the vanadium-chromium-containing filter cake is extracted and separated, and a chromium-containing product and a vanadium-containing product are obtained correspondingly. According to the method, high-value substances such as titanium, vanadium and chromium can be gradually separated and recovered, the problem that the high-value substances are difficult to separate and recover is solved, the enrichment and separation efficiency is improved, and the recovery and separation cost is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of wastewater treatment, and particularly relates to a method for enriching and separating titanium, vanadium, and chromium from titanium white waste acid. Background Art

[0002] Titanium dioxide is an important inorganic chemical pigment, mainly composed of titanium dioxide. As an important white pigment, it is widely used in industries such as coatings, inks, paints, plastics, and papermaking, and has a large industrial application volume. Therefore, the industrial production of titanium dioxide is very important.

[0003] At present, the production processes of titanium dioxide are divided into the sulfuric acid method and the chloride method. Among them, the sulfuric acid method process is used more frequently, and the sulfuric acid method titanium dioxide production process has become an important part of the chemical industry. The sulfuric acid method titanium dioxide production process mainly includes: grinding and beneficiation of titanium ore → mixing titanium concentrate with concentrated sulfuric acid and heating for acidolysis → filtering the leaching solution → heating hydrolysis, filtering and washing to obtain metatitanic acid → subjecting the salt-treated metatitanic acid to high-temperature roasting to obtain titanium dioxide. Among them, a large amount of acidic waste liquid (i.e., titanium white waste acid) will be generated in the acid leaching and hydrolysis process. People have tried to treat and recycle the titanium white waste acid to reduce its harm.

[0004] In the current sulfuric acid method titanium white process, the titanium white waste acid generated after hydrolysis still contains 5 - 10 g / L of TiO₂. Basically, the concentrated titanium white waste acid is recycled as a titanium liquid leaching agent to recover the TiO₂ therein. However, this method will cause the free sulfuric acid concentration in the titanium liquid to become higher and higher, ultimately resulting in an excessive F value and affecting the hydrolysis of the titanium liquid in the main production. For the recovery of vanadium in titanium white waste acid, the extraction process is mainly used. In the current extraction process for extracting vanadium from titanium white waste acid, the hydrolysis of titanium during extraction leads to serious emulsification, and even after several months, the oil and water phases cannot be effectively separated, resulting in large losses of the extractant and unsmooth production, poor economic benefits, and inability to continue production; usually, the separation time of the oil and water phases for extracting valuable elements by the extraction process is within a few seconds to a few minutes, and it rarely exceeds ten minutes. If the separation time requires several hours or even several days, it is basically impossible to achieve industrial production. If only the titanium in the titanium white waste acid is hydrolyzed by heating, titanium hardly hydrolyzes or redissolves after hydrolysis at high acidity; at low acidity, titanium hydrolyzes into a colloid and cannot be separated from vanadium and chromium, and it is very difficult to filter. When steel slag is used to neutralize titanium white waste acid, the traditional method is to filter and separate titanium, vanadium, and chromium ions from the neutralization slag. Due to the complex composition of the slurry, a large amount of colloid is generated and it is very difficult to filter. Many manufacturers have given up due to difficulties in filtration during pilot production. In addition, there is a literature using the extraction method to separate trivalent chromium and tetravalent vanadium. This research is mainly aimed at vanadium-chromium solutions without titanium. If titanium is not deeply removed from the titanium-vanadium-chromium solution, it will cause a large loss of the extractant, and even the oil and water phases cannot be separated, and it is impossible to economically and feasibly separate vanadium and chromium in the titanium-vanadium-chromium solution. Summary of the Invention

[0005] In view of this, the present invention provides a method for enriching and separating titanium, vanadium, and chromium from titanium white waste acid. The method of the present invention can effectively separate and recover high-value substances such as titanium, chromium, and vanadium in titanium white waste acid, solve the problem of difficult separation and recovery, improve the enrichment and separation efficiency, and reduce the difficulty and cost of recovery and separation.

[0006] The present invention provides a method for enriching and separating titanium, vanadium, and chromium from titanium white waste acid, comprising the following steps:

[0007] (A) Mix an alkaline substance with titanium white waste acid for an acid-base reaction to enrich titanium, vanadium, and chromium;

[0008] The enrichment comprises the following steps:

[0009] (A1) Mix an alkaline substance with titanium white waste acid for a preliminary acid-base neutralization reaction, then filter and wash to obtain filter cake 1 and filtrate 1 respectively;

[0010] (A2) Mix an alkaline substance with the filtrate 1 for a secondary acid-base neutralization reaction, then filter and wash to obtain titanium, vanadium, and chromium-containing filter cake 2 and filtrate 2;

[0011] (A3) Judgment: Judge the enrichment content of titanium, vanadium, and chromium in the filter cake 2. If it is qualified, proceed to step (A4); if it is unqualified, return the filter cake 2 to step (A1) to react with titanium white waste acid, recycle and enrich titanium, vanadium, and chromium until the enrichment content of titanium, vanadium, and chromium in the filter cake 2 is qualified, and then proceed to step (A4);

[0012] Among them, the qualified standard is: the TiO2 content in the dry basis ≥ 0.5%, or the V2O5 content in the dry basis ≥ 0.1%, or the Cr2O3 content in the dry basis ≥ 0.1%;

[0013] (A4) Mix the titanium, vanadium, and chromium-containing filter cake 2 with an acid solution for pulping, then filter and wash to obtain filter cake 3 and titanium, vanadium, and chromium-containing filtrate 3;

[0014] (B) Add ammonia or ammonium, freeze, filter, and wash the filtrate 3 to obtain ammonium alum crystal 4 and filtrate 4 respectively;

[0015] (C) Dilute and hydrolyze the filtrate 4, and separate to obtain the upper-layer vanadium and chromium-containing solution 5 and the lower-layer titanium-containing slurry 5 respectively;

[0016] (D) Neutralize the upper-layer vanadium and chromium-containing solution 5 with an alkaline substance, then filter and wash to obtain vanadium and chromium-containing filter cake 6 and filtrate 6 respectively;

[0017] (E) Extract and separate the vanadium and chromium-containing filter cake 6 to obtain chromium-containing product and vanadium-containing product respectively;

[0018] The extraction and separation method is method E-X or method E-Y:

[0019] The method E-X includes the following steps:

[0020] E-X1: Drying the vanadium- and chromium-containing filter cake 6 to obtain vanadium- and chromium-containing slag;

[0021] E-X2: Roasting the vanadium- and chromium-containing slag to obtain clinker; or, mixing the vanadium- and chromium-containing slag with a promoter oxidant and roasting to obtain clinker;

[0022] E-X3: Leaching the clinker, performing solid-liquid separation to respectively obtain chromium-containing slag and vanadium-containing solution;

[0023] The method E-Y includes the following steps:

[0024] E-Y1: Dissolving the vanadium- and chromium-containing filter cake 6 with sulfuric acid to obtain a vanadium- and chromium-enriched solution 7;

[0025] E-Y2: Separating and extracting the vanadium- and chromium-enriched solution 7 to respectively obtain a vanadium-containing product and a chromium-containing solution.

[0026] In step (A1), the basic substance is a calcium- and / or magnesium-containing basic substance.

[0027] In step (A1), the dosage of the basic substance is such that the pH value of the system after the preliminary acid-base neutralization reaction reaches: 0.5 < pH < 3.0.

[0028] Preferably, in step (A1), the dosage of the basic substance is such that the pH value of the system after the preliminary acid-base neutralization reaction reaches: 0.8 < pH < 1.5.

[0029] In step (A2), the basic substance is a calcium- and / or magnesium-containing basic substance.

[0030] In step (A2), the dosage of the basic substance is such that the pH value of the system after the secondary acid-base neutralization reaction reaches: 3.0 < pH < 8.0.

[0031] Preferably, in step (A2), the dosage of the basic substance is such that the pH value of the system after the secondary acid-base neutralization reaction reaches: 4 < pH < 6.0.

[0032] In step (A4), the dosage of the acid solution is such that the pH value of the system reaches: 0 < pH < 3.5.

[0033] Preferably, in step (A4), the dosage of the acid solution is such that the pH value of the system reaches: 0.5 < pH < 1.5.

[0034] In step (D), the dosage of the basic substance is such that the pH value of the system reaches: 3.5 < pH < 8.

[0035] Preferably, in step (D), the amount of the basic substance is such that the pH value of the system reaches: 4 < pH < 8.

[0036] Preferably, in step (A1), the basic substance is at least one of calcium carbonate, calcium oxide, calcium hydroxide, magnesium oxide, magnesium carbonate, magnesium hydroxide, steel slag, and blast furnace slag.

[0037] Preferably, in step (A2), the basic substance is at least one of calcium carbonate, calcium oxide, calcium hydroxide, magnesium oxide, magnesium carbonate, magnesium hydroxide, steel slag, and blast furnace slag.

[0038] In step (D), the basic substance is at least one of sodium hydroxide, sodium carbonate, ammonia water, calcium carbonate, calcium oxide, calcium hydroxide, magnesium oxide, magnesium carbonate, magnesium hydroxide, steel slag, and blast furnace slag.

[0039] In step (B), the freezing temperature is 0 to 10°C.

[0040] Preferably, step (C) specifically includes:

[0041] (C1) Add a basic substance to the filtrate 4 to adjust the pH value, then add water for dilution and hydrolysis, and then separate to obtain an upper vanadium-chromium-containing solution and a lower titanium-containing slurry respectively;

[0042] (C2) Further dilution treatment:

[0043] Use the lower titanium-containing slurry as the initial treatment object and perform N times of further dilution processes;

[0044] Each further dilution process includes: adding water to dilute the titanium-containing slurry, adding acid to adjust the pH value, standing and then separating to obtain an upper vanadium-chromium-containing solution after further dilution and a lower titanium-containing slurry after further dilution respectively;

[0045] Among them, each further dilution process uses the lower titanium-containing slurry obtained in the previous further dilution process as the treatment object; N is an integer greater than or equal to 0;

[0046] (C3) Combine all the upper vanadium-chromium-containing solutions obtained in steps (C1) to (C2) to obtain a vanadium-chromium-containing solution 5.

[0047] In step (C1), adjusting the pH value means adjusting the pH to 1 to 4.

[0048] Preferably, in step (C1), adjusting the pH value means adjusting the pH to 2.5 to 3.5.

[0049] In step (C1), the temperature of the dilution and hydrolysis is 0 to 110°C.

[0050] In step (C2), N is 0 (when N is 0, that is, step (C2) is not carried out), 1, 2, 3, 4 or 5.

[0051] In step (C2), adjusting the pH value means adjusting the pH to 1 - 4.

[0052] Preferably, in step (C2), adjusting the pH value means adjusting the pH to 2.5 - 3.5.

[0053] In step E-X2, the promoter is preferably a calcium-based promoter, a magnesium-based promoter or a sodium-based promoter; among them, the calcium-based promoter is calcium oxide; the magnesium-based promoter is magnesium oxide and / or magnesium hydroxide; the sodium-based promoter is sodium carbonate.

[0054] In step E-X2, the mass ratio of the promoter to the vanadium-chromium-containing slag is (0 - 50):50 and not 0.

[0055] In step E-X2, the roasting temperature is 750 - 1100 °C.

[0056] In step E-X2, the roasting time is 20 - 300 min.

[0057] In step E-X2 and step E-Y2, the separation and extraction method is extraction and back-extraction, adsorption and desorption, ammonium salt precipitation of vanadium or hydrolysis precipitation of vanadium.

[0058] In step E-X2, the promoter is a calcium-based promoter, the mass ratio of the calcium-based promoter to the vanadium-chromium-containing slag is (0 - 50):50 and not 0, the roasting temperature is 850 - 1100 °C, and the roasting time is 20 - 300 min;

[0059] Or, the promoter is a magnesium-based promoter, the mass ratio of the magnesium-based promoter to the vanadium-chromium-containing slag is (0 - 50):50 and not 0, the roasting temperature is 850 - 1100 °C, and the roasting time is 20 - 300 min;

[0060] Or, the promoter is a sodium-based promoter, the mass ratio of the sodium-based promoter to the vanadium-chromium-containing slag is (0 - 50):50 and not 0, the roasting temperature is 750 - 900 °C, and the roasting time is 20 - 300 min.

[0061] Preferably, the extraction and back-extraction includes: contacting the vanadium-chromium enriched liquid 7 with an extractant for extraction, and then performing back-extraction to obtain a vanadium-containing liquid and a chromium-containing liquid respectively;

[0062] Among them, the extractant is at least one of phosphoric acid extractants and amine extractants; among them, the phosphoric acid extractants are at least one of P204 extractant and P507 extractant; the amine extractants are at least one of N235 extractant and N1923 extractant;

[0063] When the extractant is an amine extractant, the vanadium-chromium enriched liquid 7 is pre-oxidized to oxidize the tetravalent vanadium therein into pentavalent vanadium, and then extraction is carried out;

[0064] The adsorption and desorption include: contacting the vanadium-chromium enriched liquid 7 with a cationic resin for resin adsorption, and then carrying out desorption to obtain a vanadium-containing liquid and a chromium-containing liquid respectively; or including: pre-oxidizing the tetravalent vanadium in the vanadium-chromium enriched liquid 7 into pentavalent vanadium, then contacting with an anionic resin for resin adsorption, and then carrying out desorption to obtain a vanadium-containing liquid and a chromium-containing liquid respectively;

[0065] Among them, the anionic resin is at least one of Rohm and Haas IRA96rf anion resin and D301 anion resin; the cationic resin is at least one of Duolite CH-91 cation resin and Duolite CH-93 cation resin;

[0066] The ammonium salt vanadium precipitation includes: oxidizing the vanadium-chromium enriched liquid 7 with an oxidant, then adding ammonium sulfate, heating and reacting, filtering, and washing to obtain a chromium-containing filtrate and a vanadium-containing filter cake respectively;

[0067] The hydrolysis vanadium precipitation includes: oxidizing the vanadium-chromium enriched liquid with an oxidant, heating and reacting, filtering, and washing to obtain a chromium-containing filtrate and a vanadium-containing filter cake respectively.

[0068] Preferably, in the extraction and stripping:

[0069] An extractant mixture is used; the extractant mixture is a mixture of an extractant, TBP and solvent oil;

[0070] In the adsorption and desorption:

[0071] When the adsorption resin is a cationic resin, the desorption includes sequentially desorbing with a sulfuric acid solution and washing with water;

[0072] When the adsorption resin is an anionic resin, the desorption includes sequentially desorbing with a sodium hydroxide solution or an ammonia water solution and washing with water;

[0073] In the ammonium salt vanadium precipitation:

[0074] The weight ratio of ammonium sulfate to vanadium pentoxide in the vanadium-chromium enriched liquid 7 is (0-10):1 and not zero;

[0075] The ammonium salt vanadium precipitation time is 0.1h to 100h;

[0076] In the hydrolysis and vanadium precipitation process:

[0077] The hydrolysis and vanadium precipitation is carried out by heating hydrolysis, and the hydrolysis temperature is 50°C to 110°C;

[0078] The hydrolysis and vanadium precipitation time is 0.1 h to 100 h.

[0079] Preferably, in step (A), after the preliminary neutralization in step (A1) is completed, filtration is not carried out, and step (A2) secondary neutralization is directly carried out;

[0080] Or, in step (A), after step (A1) is completed, steps (A2) to (A3) are not carried out, and step (B) is directly carried out; or steps (A2) to (B) are not carried out, and step (C) is directly carried out;

[0081] Or, in step (A), after step (A2) is completed, the obtained titanium-vanadium-chromium-containing filter cake 2 does not carry out steps (A3) to (D), and step (E-X) for separating vanadium and chromium is directly carried out.

[0082] The present invention provides a method for enriching and separating titanium, vanadium, and chromium from titanium white waste acid. First, an alkaline substance containing calcium and / or magnesium is mixed with the titanium white waste acid for an acid-base neutralization reaction to reduce the acidity of the titanium white waste acid and precipitate titanium, vanadium, and chromium. Then, it is redissolved with sulfuric acid to obtain a filtrate containing titanium, vanadium, and chromium; then, the filtrate containing titanium, vanadium, and chromium is frozen, filtered, and washed to obtain ammonium aluminum sulfate crystals and a filtrate containing titanium, vanadium, and chromium respectively; then, the filtrate containing titanium, vanadium, and chromium is diluted and hydrolyzed, and the pH value is adjusted to hydrolyze titanyl sulfate while the vanadium and chromium sulfates do not hydrolyze, and metatitanic acid slurry and a diluted vanadium-chromium-containing solution are separated; after that, the diluted vanadium-chromium-containing solution is neutralized and filtered to obtain a vanadium-chromium-containing filter cake; then, extraction and separation are carried out on the vanadium-chromium-containing filter cake. One of the extraction and separation methods is the roasting and leaching method, and the second method is the acid dissolution and enrichment separation method. Through extraction and separation, chromium-containing products and vanadium-containing products are obtained respectively. The method of the present invention can gradually separate and recover these high-value substances of titanium, chromium, and vanadium, solves the problem of their difficult separation and recovery, improves the enrichment and separation efficiency, and reduces the difficulty and cost of recovery and separation. Brief Description of the Drawings

[0083] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained according to the provided drawings without creative efforts.

[0084] Figure 1 It is the process flow chart of the method of the present invention. Detailed Embodiments

[0085] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field to which this application belongs. The terms used in the specification of this application are for the purpose of describing specific embodiments only and are not intended to limit this application.

[0086] In this text, among the technical features described in an open-ended manner, a closed technical solution composed of the listed features is included, as well as an open technical solution containing the listed features.

[0087] The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0088] In this text, regarding a numerical range, unless otherwise specified, the above numerical range is considered continuous and includes the minimum and maximum values of this range, as well as each value between such minimum and maximum values. Further, when the range refers to integers, it includes each integer between the minimum and maximum values of this range. In addition, when multiple ranges are provided to describe features or characteristics, these ranges can be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all sub-ranges subsumed therein.

[0089] In this text, regarding the unit of a data range, if the unit is only attached after the right endpoint, it means that the units of the left endpoint and the right endpoint are the same. For example, 0 to 10 °C means that the units of the left endpoint "0" and the right endpoint "10" are both °C.

[0090] The present invention provides a method for enriching and separating titanium, vanadium, and chromium from waste titanium white acid, comprising the following steps:

[0091] (A) Mix an alkaline substance with waste titanium white acid to conduct an acid-base reaction to enrich titanium, vanadium, and chromium;

[0092] The enrichment includes the following steps:

[0093] (A1) Mix an alkaline substance with waste titanium white acid to conduct a preliminary acid-base neutralization reaction, and then filter and wash to obtain filter cake 1 and filtrate 1 respectively;

[0094] (A2) Mix an alkaline substance with the filtrate 1 to conduct a secondary acid-base neutralization reaction, and then filter and wash to obtain a filter cake 2 containing titanium, vanadium, and chromium and filtrate 2;

[0095] (A3) Judgment: Judge the enrichment content of titanium, vanadium, and chromium in the filter cake 2. If it is qualified, proceed to step (A4); if it is unqualified, return the filter cake 2 to step (A1) to react with waste titanium white acid, recycle and enrich titanium, vanadium, and chromium until the enrichment content of titanium, vanadium, and chromium in the filter cake 2 is qualified, and then proceed to step (A4);

[0096] Among them, the qualified criteria are as follows: the TiO2 content in the dry basis is ≥ 0.5%, or the V2O5 content in the dry basis is ≥ 0.1%, or the Cr2O3 content in the dry basis is ≥ 0.1%.

[0097] (A4) Mix and beat the titanium-vanadium-chromium-containing filter cake 2 with an acid solution, and then filter and wash to obtain a filter cake 3 and a titanium-vanadium-chromium-containing filtrate 3.

[0098] (B) Add ammonia or ammonium to the filtrate 3, freeze, filter, and wash to obtain ammonium alum crystals 4 and a filtrate 4 respectively.

[0099] (C) Dilute and hydrolyze the filtrate 4, and separate to obtain an upper-layer vanadium-chromium-containing solution 5 and a lower-layer titanium-containing slurry 5 respectively.

[0100] (D) Neutralize the upper-layer vanadium-chromium-containing solution 5 with an alkaline substance, and then filter and wash to obtain a vanadium-chromium-containing filter cake 6 and a filtrate 6 respectively.

[0101] (E) Extract and separate the vanadium-chromium-containing filter cake 6 to obtain a chromium-containing product and a vanadium-containing product respectively.

[0102] The extraction and separation method is Method E-X or Method E-Y:

[0103] The Method E-X includes the following steps:

[0104] E-X1: Dry the vanadium-chromium-containing filter cake 6 to obtain a vanadium-chromium-containing residue.

[0105] E-X2: Mix the vanadium-chromium-containing residue with a co-oxidant, roast to obtain a clinker.

[0106] E-X3: Leach the clinker, separate the solid and liquid to obtain a chromium-containing residue and a vanadium-containing solution respectively.

[0107] The Method E-Y includes the following steps:

[0108] E-Y1: Dissolve the vanadium-chromium-containing filter cake 6 with sulfuric acid to obtain a vanadium-chromium enriched solution 7.

[0109] E-Y2: Separate and extract the vanadium-chromium enriched solution 7 to obtain a vanadium-containing product and a chromium-containing solution respectively.

[0110] See Figure 1 , Figure 1 , which is the process flow chart of the method of the present invention.

[0111] In this text, the numbers after the filtrate and filter cake (such as the numbers 1, 2, 3, etc. after filtrate 1, filtrate 2, filtrate 3, filter cake 1, filter cake 2, filter cake 3) do not impose any special restrictions on the filtrate and filter cake themselves. Since filter cakes and filtrates appear in multiple steps, the addition of numbers is only for correspondence with each step, facilitating an intuitive representation of which step's filter cake or filtrate it is.

[0112] Regarding step (A) :

[0113] (A) Mix an alkaline substance with titanium white waste acid to carry out an acid-base reaction for enriching titanium, vanadium, and chromium.

[0114] In the present invention, the enrichment includes the following steps:

[0115] (A1) Mix an alkaline substance with titanium white waste acid to carry out a preliminary acid-base neutralization reaction, and then filter and wash to obtain filter cake 1 and filtrate 1 respectively;

[0116] (A2) Mix an alkaline substance with the filtrate 1 to carry out a secondary acid-base neutralization reaction, and then filter and wash to obtain titanium-vanadium-chromium-containing filter cake 2 and filtrate 2;

[0117] (A3) Judgment: Judge the enrichment content of titanium, vanadium, and chromium in the filter cake 2. If it is qualified, proceed to step (A4); if it is unqualified, return the filter cake 2 to step (A1) to react with titanium white waste acid, and recycle to enrich titanium, vanadium, and chromium until the enrichment content of titanium, vanadium, and chromium in the filter cake 2 is qualified, and then proceed to step (A4);

[0118] Among them, the qualified standard is: the TiO2 content in the dry basis ≥ 0.5%, or the V2O5 content in the dry basis ≥ 0.1%, or the Cr2O3 content in the dry basis ≥ 0.1%;

[0119] (A4) Mix the titanium-vanadium-chromium-containing filter cake 2 with an acid solution for pulping, and then filter and wash to obtain filter cake 3 and titanium-vanadium-chromium-containing filtrate 3.

[0120] Regarding step (A1):

[0121] In the present invention, the alkaline substance is preferably an alkaline substance containing calcium and / or magnesium, more preferably at least one of calcium carbonate, calcium oxide, calcium hydroxide, magnesium oxide, magnesium carbonate, magnesium hydroxide, steel slag, and blast furnace slag. The present invention introduces the above alkaline substance to carry out an acid-base neutralization reaction with titanium white waste acid, reduce the acidity of titanium white waste acid, and co-precipitate titanium, vanadium, and chromium in titanium white waste acid.

[0122] In the present invention, the dosage of the alkaline substance is preferably such that the pH value of the system after the preliminary acid-base neutralization reaction reaches: 0.5 < pH < 3.0, specifically it can be 1, 1.1, 1.5, 2.0, 2.5, and more preferably 0.8 < pH < 1.5.

[0123] In the present invention, the mixing method is preferably stirring and mixing. The temperature of the stirring and mixing is preferably 0 to 80 °C, more preferably 0 to 60 °C. The time of the stirring and mixing is preferably 0.1 to 50 h, specifically it can be 2 h, 3 h, 4 h, 5 h, 10 h, 15 h, 20 h, 30 h, 40 h.

[0124] In the present invention, after the acid-base preliminary neutralization reaction is carried out by mixing, filtration and washing are carried out. Among them, the washing is carried out with water. After filtration and washing, filter cake 1 (wet filter cake) and filtrate 1 are obtained respectively.

[0125] Among them, the volume ratio of the water used for washing to the volume of filter cake 1 is preferably (10 to 0):1 and not 0, specifically it can be 10:1, 9:1, 8:1, 7:1, 6:1, 5:1, 4:1, 3:1, 2:1, 1:1.

[0126] Regarding step (A2):

[0127] In the present invention, the basic substance is preferably a basic substance containing calcium and / or magnesium, more preferably at least one of calcium carbonate, calcium oxide, calcium hydroxide, magnesium oxide, magnesium carbonate, magnesium hydroxide, steel slag, blast furnace slag.

[0128] In the present invention, the dosage of the basic substance is preferably such that the pH value of the system after the acid-base secondary neutralization reaction reaches: 3.0 < pH < 8.0, specifically it can be 3.5, 4.0, 4.4, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, 7.5, more preferably 4 < pH < 6.0.

[0129] In the present invention, after the acid-base secondary neutralization reaction is carried out by mixing, filtration and washing are carried out. Among them, the washing is carried out with water. After filtration and washing, filter cake 2 (wet filter cake) and filtrate 2 are obtained respectively.

[0130] Regarding step (A3):

[0131] Determination: Determine the enriched content of titanium, vanadium and chromium in the filter cake 2. If it is qualified, step (A4) is carried out; if it is unqualified, the filter cake 2 is returned to step (A1) to react with titanium white waste acid, and titanium, vanadium and chromium are cyclically enriched until the enriched content of titanium, vanadium and chromium in the filter cake 2 is qualified, and then step (A4) is carried out; among them, the qualified standard is: the TiO2 content in the dry basis ≥ 0.5%, or the V2O5 content in the dry basis ≥ 0.1%, or the Cr2O3 content in the dry basis ≥ 0.1%.

[0132] In the present invention, after the end of step (A2), if the enriched content of titanium, vanadium, and chromium in the filter cake 2 is not high (i.e., lower than the standard shown above), the obtained filter cake 2 is returned to step (A1) to react with titanium white waste acid, and titanium, vanadium, and chromium are cyclically enriched until the enriched content of titanium, vanadium, and chromium in the filter cake 2 is qualified, and then the subsequent step (A4) is carried out. After the end of step (A2), if the enriched content of titanium, vanadium, and chromium in the filter cake 2 is high (i.e., meets the standard shown above), the subsequent step (A4) is directly carried out.

[0133] Regarding step (A4):

[0134] In the present invention, after the titanium-vanadium-chromium coprecipitation is obtained in the previous steps and treated, an acid solution is used to dissolve it reversely to obtain a solution containing titanium, vanadium, and chromium. Specifically: the filter cake 2 containing titanium, vanadium, and chromium is mixed and slurried with an acid solution, and then filtered and washed to obtain a filter cake 3 and a filtrate 3 containing titanium, vanadium, and chromium.

[0135] In the present invention, the acid solution is preferably a sulfuric acid solution and / or titanium white waste acid. Among them, the sulfuric acid solution is preferably concentrated sulfuric acid.

[0136] In the present invention, the dosage of the acid solution is preferably such that the pH value of the system reaches 0 < pH < 3.5, more preferably 0.5 < pH < 1.5, specifically 0.7, 0.9, 1.0, 1.1, 1.2, and still more preferably 0.8 < pH < 1.5.

[0137] In the present invention, the mixing and slurrying time is preferably 0.1 - 50 h, more preferably 1 - 10 h, specifically 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, 10 h, 20 h, 30 h, 40 h.

[0138] In the present invention, after slurrying, filtration and washing are carried out. Among them, the washing is carried out with water. After the above treatment, a filter cake 3 and a filtrate 3 containing titanium, vanadium, and chromium are obtained respectively.

[0139] Among them, the dosage ratio of the water used for washing to the filter cake 2 is preferably (0 - 100) L∶14637 g and not 0, specifically 1 L∶14637 g, 5 L∶14637 g, 10 L∶14637 g, 18 L∶14637 g, 20 L∶14637 g, 30 L∶14637 g, 40 L∶14637 g, 50 L∶14637 g, 60 L∶14637 g, 70 L∶14637 g, 80 L∶14637 g, 90 L∶14637 g, 100 L∶14637 g.

[0140] Regarding step (B) :

[0141] (B) Ammonia or ammonium is added to the filtrate 3, followed by freezing, filtration, and washing to obtain ammonium alum crystals 4 and filtrate 4 respectively.

[0142] In the present invention, the ammonia is preferably at least one of aqueous ammonia and liquid ammonia. The ammonium is preferably at least one of ammonium sulfate, ammonium bisulfate, ammonium carbonate, ammonium bicarbonate, ammonium sulfite, and ammonium bisulfite. The dosage of the ammonia or ammonium is preferably 0 to 10 times the equivalent amount of ammonium alum generated, more preferably 0.9 to 1.1, and specifically can be 0.95, 1.0, or 1.05.

[0143] In the present invention, after obtaining the titanium-vanadium-chromium-containing filtrate 3 in step (A), it is frozen. The freezing temperature is preferably 0 to 10 °C, and specifically can be 0 °C, 1 °C, 2 °C, 3 °C, 4 °C, 5 °C, 6 °C, 7 °C, 8 °C, 9 °C, or 10 °C.

[0144] In the present invention, after the above freezing, filtration and washing are carried out. Among them, the washing is preferably water washing. The volume ratio of the water to the filtrate 3 is preferably (0 to 10):1 and not 0, more preferably 0.2:1 or 0.5:1. After the above filtration and washing, ammonium alum crystals (specifically ammonium alum dodecahydrate crystals) and filtrate 4 are obtained respectively.

[0145] Regarding step (C) :

[0146] (C) Dilute and hydrolyze the filtrate 4, and separate to obtain an upper-layer vanadium-chromium-containing solution 5 and a lower-layer titanium-containing slurry 5 respectively.

[0147] In the present invention, step (C) preferably specifically includes:

[0148] (C1) Add an alkaline substance to the filtrate 4 to adjust the pH value, then add water for dilution and hydrolysis, and then separate to obtain an upper-layer vanadium-chromium-containing solution and a lower-layer titanium-containing slurry respectively;

[0149] (C2) Further dilution treatment:

[0150] Use the lower-layer titanium-containing slurry as the initial treatment object and carry out N times of further dilution procedures;

[0151] Each further dilution procedure includes: adding water to dilute the titanium-containing slurry, adding an acid to adjust the pH value, standing and then separating to obtain an upper-layer vanadium-chromium-containing solution after further dilution and a lower-layer titanium-containing slurry after further dilution respectively;

[0152] Among them, each further dilution procedure uses the lower-layer titanium-containing slurry obtained in the previous further dilution procedure as the treatment object; N ≥ 1;

[0153] (C3) Combine all the upper-layer vanadium-chromium-containing solutions obtained in steps (C1) to (C2) to obtain a vanadium-chromium-containing solution 5.

[0154] In step (C1):

[0155] The basic substance is preferably at least one of magnesium hydroxide, calcium hydroxide, sodium hydroxide, sodium carbonate, and ammonia water. The dosage of the basic substance is preferably such that the pH value reaches 1 to 4, specifically 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, and more preferably 2.5 to 3.5. After adjusting the pH value as described above, it is diluted with water for hydrolysis, and the diluted liquid is 0 to 10,000 times the volume of the filtrate before dilution, more preferably 3 to 100 times, specifically 4.8 times. The temperature of the dilution hydrolysis is preferably 0 to 110 °C, specifically 0 °C, 10 °C, 20 °C, 30 °C, 40 °C, 50 °C, 60 °C, 70 °C, 80 °C, 90 °C, 100 °C, 110 °C. The time of the dilution hydrolysis is preferably 0.01 to 100 h, more preferably 1 to 50 h, further preferably 1 to 10 h, specifically 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, 10 h.

[0156] After the above dilution hydrolysis, the system is layered into an upper vanadium-chromium-containing dilution solution and a lower titanium-containing slurry (metatitanic acid slurry), and then separated to obtain an upper vanadium-chromium-containing solution and a lower titanium-containing slurry respectively.

[0157] In step (C2):

[0158] After separating the lower titanium-containing slurry obtained in step (C1), a re-dilution treatment is carried out. Specifically: taking the titanium-containing slurry obtained in step (C1) as the initial treatment object, N re-dilution processes are carried out. Each re-dilution process includes: diluting the titanium-containing slurry with water and adjusting the pH value with acid, and separating after standing to obtain an upper vanadium-chromium-containing solution after re-dilution and a lower titanium-containing slurry after re-dilution respectively. Among them, each re-dilution process takes the lower titanium-containing slurry after re-dilution obtained in the previous re-dilution process as the treatment object; N is an integer ≥ 0; preferably 0, 1, 2, 3, 4, or 5.

[0159] In each re-dilution process, the degree of dilution is preferably: the volume of the slurry after dilution is 1 to 100 times the volume of the slurry before dilution, more preferably 1 to 50 times, further preferably 5 to 20 times, and most preferably 10 times. After dilution with water, the pH value is adjusted with acid, preferably adjusted to 1 to 4, specifically 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, and in some embodiments is 3.16. The acid used is preferably sulfuric acid; the sulfuric acid can be a fresh sulfuric acid solution or a waste sulfuric acid solution. Then, it is allowed to stand; the standing time is preferably 0 to 100 h, more preferably 1 to 50 h, further preferably 1 to 10 h, and in some embodiments is 5 h. After standing, the system is layered again into an upper vanadium-chromium-containing dilution solution and a lower titanium-containing slurry (metatitanic acid slurry), and then separated to obtain an upper vanadium-chromium-containing solution after re-dilution and a lower titanium-containing slurry after re-dilution respectively.

[0160] In step (C3):

[0161] After steps (C1) to (C2), all the upper-layer vanadium- and chromium-containing solutions obtained in these two steps are combined to obtain vanadium- and chromium-containing solution 5.

[0162] In the present invention, after the final lower-layer titanium-containing slurry is obtained after steps (C1) to (C2), it can be reversely dissolved with sulfuric acid to obtain titanium solution and returned to the main process of titanium white production, or it can be filtered to obtain metatitanic acid filter cake, which becomes a titanium-rich raw material. Among them, the recovery rate of TiO2 in the lower-layer titanium-containing slurry can reach more than 95%, that is, most of the titanium is separated and recovered into the lower-layer titanium slurry.

[0163] Through step (C), the present invention enriches titanium into the titanium slurry and separates it to obtain metatitanic acid slurry, and enriches vanadium and chromium into the vanadium- and chromium-containing solution, thereby realizing the separation of titanium and vanadium and chromium.

[0164] Regarding step (D) :

[0165] (D) Neutralize the vanadium- and chromium-containing solution 5 with an alkaline substance, and then filter and wash to obtain vanadium- and chromium-containing filter cake 6 and filtrate 6 respectively.

[0166] In the present invention, the alkaline substance is preferably at least one of sodium hydroxide, sodium carbonate, ammonia water, calcium carbonate, calcium oxide, calcium hydroxide, magnesium oxide, magnesium carbonate, magnesium hydroxide, steel slag, blast furnace slag. The present invention introduces the above alkaline substance to neutralize the vanadium- and chromium-containing solution, reduce the acidity of the vanadium- and chromium-containing solution, and precipitate vanadium and chromium therein.

[0167] In the present invention, the dosage of the alkaline substance is preferably such that the pH value of the system reaches: 3.5 < pH < 8, preferably 4 < pH < 8, and specifically can be 4.5, 5.0, 5.4, 5.5, 6.0, 6.5, 7.0, 7.5.

[0168] In the present invention, after the above neutralization, filtration and washing are carried out. Among them, the washing is preferably water washing. The volume ratio of the water to the vanadium- and chromium-containing solution is preferably (0 to 1):1, and specifically can be 0.01:1, 0.02:1, 0.03:1, 0.04:1, 0.05:1, 0.1:1, 0.5:1, 1:1. After the above filtration and washing, vanadium- and chromium-containing filter cake 6 and filtrate 6 are obtained respectively.

[0169] Regarding step (E) :

[0170] (E) Extract and separate the vanadium- and chromium-containing filter cake 6 to obtain chromium-containing product and vanadium-containing product respectively.

[0171] In the present invention, after obtaining the vanadium- and chromium-containing filter cake 6 in step (D), extraction and separation are performed on it to separate chromium from vanadium. In the present invention, the extraction and separation methods are mainly divided into two categories: method E-X and method E-Y; the following is a specific introduction.

[0172] (1) Method E-X:

[0173] Method E-X is a roasting and leaching method, which includes the following steps:

[0174] E-X1: Dry the vanadium- and chromium-containing filter cake 6 to obtain vanadium- and chromium-containing slag;

[0175] E-X2: Roast the vanadium- and chromium-containing slag to obtain clinker; or, mix the vanadium- and chromium-containing slag with a co-oxidant and roast to obtain clinker;

[0176] E-X3: Leach the clinker, perform solid-liquid separation to obtain chromium-containing slag and vanadium-containing liquid respectively.

[0177] In step E-X1:

[0178] The drying temperature is preferably 20 - 500 °C, more preferably 50 - 200 °C, further preferably 50 - 150 °C, and most preferably 100 °C. After drying, vanadium- and chromium-containing slag is obtained.

[0179] In step E-X2:

[0180] The co-oxidant is preferably a calcium-based co-oxidant, a magnesium-based co-oxidant or a sodium-based co-oxidant. Among them, the calcium-based co-oxidant is preferably calcium oxide; the magnesium-based co-oxidant is preferably magnesium oxide and / or magnesium hydroxide. The sodium-based co-oxidant is preferably sodium carbonate.

[0181] Mix the vanadium- and chromium-containing slag with the co-oxidant and then roast. The mixing is preferably grinding and mixing to be fully mixed. The mass ratio of the co-oxidant to the vanadium- and chromium-containing slag is preferably (0 - 50):50 and not 0, specifically can be 1:50, 5:50, 8:50, 15:50, 17:50, 20:50, 25:50, 30:50. For the two cases of not using a co-oxidant and using a co-oxidant, the roasting temperature is preferably 750 - 1100 °C, specifically can be 850 - 1100 °C, 750 - 900 °C. The roasting time is preferably 20 - 300 min, specifically can be 20 min, 50 min, 1 h, 2 h, 3 h, 4 h, 5 h.

[0182] Depending on the different promoters, the control of the roasting process is different. That is, step E-X2 can be: mixing the vanadium-chromium-containing slag with a calcium-based promoter and performing calcination roasting to obtain a clinker; or, mixing the vanadium-chromium-containing slag with a magnesium-based promoter and performing magnesia roasting to obtain a clinker; or, mixing the vanadium-chromium-containing slag with a sodium-based promoter and performing sodium roasting to obtain a clinker.

[0183] Regarding calcination roasting: The mass ratio of the calcium-based promoter to the vanadium-chromium-containing slag is preferably (0-50):50 and not 0, and specifically can be 1:50, 5:50, 8:50, 15:50, 17:50, 20:50, 25:50, 30:50, and more preferably 8:50. The temperature of the calcination roasting is preferably 850-1100 °C, and specifically can be 850 °C, 860 °C, 870 °C, 880 °C, 890 °C, 900 °C, 910 °C, 920 °C, 930 °C, 940 °C, 950 °C, 960 °C, 970 °C, 980 °C, 990 °C, 1000 °C, 1010 °C, 1020 °C, 1030 °C, 1040 °C, 1050 °C, 1060 °C, 1070 °C, 1080 °C, 1090 °C, 1100 °C. The time of the calcination roasting is preferably 20-300 min, and specifically can be 20 min, 50 min, 1 h, 2 h, 3 h, 4 h, 5 h.

[0184] Regarding magnesia roasting: The mass ratio of the magnesium-based promoter to the vanadium-chromium-containing slag is preferably (0-50):50 and not 0, and specifically can be 1:50, 5:50, 8:50, 15:50, 17:50, 20:50, and more preferably 8:50. The temperature of the magnesia roasting is preferably 850-1100 °C, and specifically can be 850 °C, 860 °C, 870 °C, 880 °C, 890 °C, 900 °C, 910 °C, 920 °C, 930 °C, 940 °C, 950 °C, 960 °C, 970 °C, 980 °C, 990 °C, 1000 °C, 1010 °C, 1020 °C, 1030 °C, 1040 °C, 1050 °C, 1060 °C, 1070 °C, 1080 °C, 1090 °C, 1100 °C. The time of the magnesia roasting is preferably 20-300 min, and specifically can be 20 min, 50 min, 1 h, 2 h, 3 h, 4 h, 5 h.

[0185] Regarding sodium roasting: The mass ratio of the sodium-based promoter to the vanadium-chromium-containing slag is preferably (0-50):50 and not 0, specifically it can be 1:50, 5:50, 8:50, 15:50, 17:50, 20:50, 25:50, 30:50, and more preferably 17:50. The temperature of the sodium roasting is preferably 750-900 °C, specifically it can be 750 °C, 760 °C, 770 °C, 780 °C, 790 °C, 800 °C, 810 °C, 820 °C, 830 °C, 840 °C, 850 °C, 860 °C, 870 °C, 880 °C, 890 °C, 900 °C. The time of the sodium roasting is preferably 20-300 min, specifically it can be 20 min, 50 min, 1 h, 2 h, 3 h, 4 h, 5 h.

[0186] After roasting, clinker is obtained. Preferably, the clinker is ground. The particle size of the grinding is preferably -50 to -500 mesh, and more preferably -200 mesh.

[0187] In step E-X3:

[0188] The leaching is preferably acid leaching or water leaching. For the clinker obtained by calcification roasting and magnesia roasting, acid leaching is carried out; for the clinker obtained by sodium roasting, water leaching is carried out.

[0189] The acid leaching includes: mixing and leaching the clinker with water and sulfuric acid. Among them, the dosage ratio of the water to the vanadium-chromium-containing slag is preferably (30-500) mL:50 g, specifically it can be 30 mL:50 g, 100 mL:50 g, 150 mL:50 g, 200 mL:50 g, 250 mL:50 g, 300 mL:50 g, 350 mL:50 g, 400 mL:50 g. The mass percentage concentration of the sulfuric acid is preferably 1% - 50%. The dosage of the sulfuric acid is preferably such that the pH value of the system is maintained at 0.5-6, specifically it can be 1, 2, 3, 4, 5, and more preferably 1-3. The time of the leaching is preferably 0.1-100 h, more preferably 1-50 h, further preferably 1-10 h, specifically it can be 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, 10 h.

[0190] The water leaching includes: mixing the clinker with water for leaching. Among them, the dosage ratio of water to the vanadium- and chromium-containing slag is preferably (30 - 500) mL∶50 g, specifically it can be 30 mL:50 g, 100 mL:50 g, 150 mL:50 g, 200 mL:50 g, 250 mL:50 g, 300 mL:50 g, 350 mL:50 g, 400 mL:50 g. The leaching time is preferably 0.1 - 10 h, specifically it can be 0.1 h, 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, 10 h, and more preferably 2 h. During the leaching process, the pH value of the system is maintained at 8 - 14, specifically it can be 8, 8.5, 9, 9.2, 9.5, 10, 10.5, 11, 11.5, 12, 12.5, 13, 13.5, 14.

[0191] After leaching, solid-liquid separation is carried out. The way of solid-liquid separation is preferably filtration. Through solid-liquid separation, chromium-containing slag and vanadium-containing liquid are obtained respectively.

[0192] (II) Method E-Y:

[0193] Method E-Y is an acid dissolution enrichment separation method, which includes the following steps:

[0194] E-Y1: Dissolve the vanadium- and chromium-containing filter cake 6 with sulfuric acid to obtain a vanadium- and chromium-enriched liquid 7;

[0195] E-Y2: Separate and extract the vanadium- and chromium-enriched liquid 7 to obtain a vanadium-containing product and a vanadium-containing liquid respectively.

[0196] In step E-Y1:

[0197] The dosage of the sulfuric acid is preferably to keep the pH value of the system at 1 - 3.8, specifically it can be 1, 1.5, 1.74, 2, 3, 3.5.

[0198] In step E-Y2:

[0199] The way of separation and extraction can be extraction and back-extraction, adsorption and desorption, ammonium salt vanadium precipitation or hydrolysis vanadium precipitation.

[0200] Regarding extraction and back-extraction:

[0201] The extraction and stripping include: contacting the vanadium-chromium enriched solution 7 with an extractant for extraction, and then performing stripping to obtain a vanadium-containing solution and a chromium-containing solution respectively. Among them, the extractant is preferably at least one of phosphoric acid-based extractants and amine-based extractants. Among them, the phosphoric acid-based extractant is preferably at least one of P204 extractant and P507 extractant. The amine-based extractant is preferably at least one of N235 extractant and N1923 extractant. When using an extractant, it is preferably to use the following extractant mixture: a mixture of an extractant, TBP (i.e., tributyl phosphate) and solvent oil. Among them, the solvent oil is preferably 260# solvent oil. In the present invention, the mass percentages of the extractant, TBP and solvent oil in the extractant mixture are preferably 10% - 30%, 0.1% - 10%, and 60% - 90% respectively. In some embodiments of the present invention, they are 20%, 5%, and 75%. The extraction is preferably multi-stage extraction, more preferably 2 - 10 stages, specifically 2 stages, 3 stages, 4 stages, 5 stages, 6 stages, 7 stages, 8 stages, 9 stages, 10 stages, and in some embodiments of the present invention, it is 5 stages. In each stage of extraction, the volume ratio of the oil phase / water phase (i.e., O / A) is preferably (10 - 0.1):1, specifically 10:1, 9:1, 8:1, 7:1, 6:1, 5:1, 4:1, 3:1, 2:1, 1:1, 0.1:1, and more preferably 2:1. The extraction pH value is preferably 1 - 3, specifically 1.2, 1.5, 2.0, 2.5. After extraction, most of the vanadium is extracted into the extraction phase, and chromium enters the raffinate (to obtain a chromium-containing solution), thereby realizing the separation of vanadium and chromium. After the extraction is completed, stripping is carried out, specifically countercurrent stripping. Through stripping, vanadium returns to the aqueous phase again to obtain a vanadium-containing solution.

[0202] When using a phosphoric acid-based extractant, tetravalent vanadium in the vanadium-chromium enriched solution 7 is extracted to separate vanadium and chromium, and direct extraction of the vanadium-chromium enriched solution can be carried out. The conditions of the extraction (such as the number of extraction stages, reagent ratio, etc.) are the same as those described above and will not be elaborated here. After the extraction is completed, stripping is carried out, specifically countercurrent stripping. The stripping agent used for stripping is preferably sulfuric acid. The concentration of the sulfuric acid is preferably 5% - 30%, and in some embodiments of the present invention, it is 20%.

[0203] When an amine extractant is used, it is to extract pentavalent vanadium in the vanadium-chromium enriched solution 7 to separate vanadium and chromium. It is not possible to directly extract the vanadium-chromium enriched solution 7, but rather to pre-oxidize the vanadium-chromium enriched solution 7 to oxidize tetravalent vanadium therein to pentavalent vanadium, and then perform extraction. Specifically, the vanadium-chromium enriched solution 7 is oxidized using an oxidant, and then extracted using an amine extractant. Among them, the oxidant is preferably at least one of hydrogen peroxide, chlorate, hypochlorite, and persulfate; among them, the concentration of the hydrogen peroxide is preferably 2% to 30%, more preferably 30%. The dosage of the oxidant is preferably 1 to 3 times the reaction equivalent of oxidizing tetravalent vanadium to pentavalent vanadium. After oxidation, extraction is carried out. The conditions of the extraction (such as the number of extraction stages, reagent ratio, etc.) are the same as those described above and will not be elaborated here. After the extraction is completed, back-extraction is carried out, specifically countercurrent back-extraction. The back-extraction agent used for the back-extraction is preferably a sodium hydroxide solution (i.e., an aqueous solution of sodium hydroxide) or ammonia water. The concentration of the back-extraction agent is preferably 3% to 25%, and specifically can be 3%, 5%, 10%, 15%, 20%, 25%.

[0204] Regarding adsorption and desorption:

[0205] The adsorption and desorption include: contacting the vanadium-chromium enriched solution 7 with a cationic resin for resin adsorption, and then performing desorption to obtain a vanadium-containing solution and a chromium-containing solution respectively; or include: pre-oxidizing tetravalent vanadium in the vanadium-chromium enriched solution 7 to pentavalent vanadium, then contacting it with an anionic resin for resin adsorption, and then performing desorption to obtain a vanadium-containing solution and a chromium-containing solution respectively. In the present invention, the binding ability of vanadium in the vanadium-chromium enriched solution 7 (the oxidized vanadium-chromium enriched solution) to the resin is stronger than that of chromium, and the adsorption ratio by the resin is greater than that of chromium. After adsorption and desorption, the vanadium-chromium ratio in the adsorption residual solution becomes smaller, and the vanadium-chromium ratio in the desorption solution increases, realizing separation.

[0206] Among them, the cationic resin is preferably at least one of Duolite CH-91 cationic resin and Duolite CH-93 cationic resin. The anionic resin is preferably at least one of Rohm and Haas IRA96rf anion resin and D301 anion resin. The saturated equivalent of the resin for adsorbing metallic vanadium is between 3.5 and 5 g / 100 mL. The oxidant used for the oxidation is preferably at least one of hydrogen peroxide, chlorate, hypochlorite, and persulfate; among them, the concentration of the hydrogen peroxide is preferably 2% to 30%, more preferably 30%. The dosage of the oxidant is preferably 1 to 3 times the reaction equivalent of oxidizing tetravalent vanadium to pentavalent vanadium. The adsorption is dynamic adsorption or static adsorption. The adsorption time is preferably 0.1 to 100 h, more preferably 1 to 50 h, and further preferably 1 to 24 h. Through the above adsorption process, most of the vanadium in the vanadium-chromium enriched solution is adsorbed by the resin, while most of the chromium enters the adsorption residual solution (obtaining a chromium-containing solution), thereby realizing the separation of vanadium and chromium.

[0207] After the above resin adsorption, desorption is carried out. For the case of using cation resin for exchange adsorption, its desorption preferably includes successively desorbing with sulfuric acid solution and then washing with water. Among them, the concentration of the sulfuric acid solution is preferably 3% - 30%, more preferably 20%. For the case of using anion resin for exchange adsorption, its desorption preferably includes successively desorbing with sodium hydroxide solution / ammonia water solution and then washing with water. Among them, the concentration of the sodium hydroxide solution or ammonia water is preferably 3% - 25%, more preferably 10%. Through the above desorption, the vanadium adsorbed on the resin enters the desorption solution, and a vanadium-containing solution is obtained.

[0208] Regarding vanadium precipitation with ammonium salts:

[0209] The vanadium precipitation with ammonium salts includes: oxidizing the vanadium-chromium enriched liquid 7 with an oxidant, then adding ammonium sulfate, heating for reaction, filtering, and washing to respectively obtain a chromium-containing filtrate and a vanadium-containing filter cake.

[0210] When carrying out vanadium precipitation with ammonium salts in the present invention, it is to precipitate pentavalent vanadium, so it is not possible to directly add ammonium salts to precipitate the vanadium-chromium enriched liquid. Instead, the vanadium-chromium enriched liquid is pre-oxidized to oxidize the tetravalent vanadium in it into pentavalent vanadium. Among them, the oxidant is preferably at least one of hydrogen peroxide, chlorate, hypochlorite, persulfate; among them, the concentration of the hydrogen peroxide is preferably 2% - 30%, more preferably 30%. The dosage of the oxidant is preferably 1 - 3 times the reaction equivalent of oxidizing tetravalent vanadium into pentavalent vanadium, specifically 1.5 times.

[0211] After the above oxidation, ammonium sulfate is added. The weight ratio of the dosage of the ammonium sulfate to the vanadium in the vanadium-chromium enriched liquid 7 is preferably (0.1 - 10)∶1, specifically 0.1∶1, 1∶1, 2∶1, 3∶1, 4∶1, 5∶1, 6∶1, 7∶1, 8∶1, 9∶1, 10∶1.

[0212] The degree of heating is preferably heating to boiling. After heating to boiling, continue to maintain heating for 0.1 - 10 h, specifically 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, 10 h. Stirring is preferably accompanied during the process of maintaining heating. During the above heating process, ammonium sulfate reacts with pentavalent vanadium in the vanadium-chromium enriched liquid to form ammonium polyvanadate precipitate.

[0213] After the above heating reaction, filtration and washing are carried out. Among them, the washing is preferably washing with water. The volume ratio of the water to the vanadium-chromium enriched liquid is preferably (0 - 10)∶1 and not 0, specifically 0.5∶1, 1∶1, 2∶1, 3∶1, 4∶1, 5∶1, 6∶1, 7∶1, 8∶1, 9∶1, 10∶1. After the above filtration and washing, a vanadium-containing filter cake and a chromium-containing filtrate are respectively obtained.

[0214] In the present invention, after obtaining the vanadium-containing filter cake, it is preferably further subjected to calcination treatment to obtain a vanadium-containing product. Among them, the temperature of the calcination is preferably 450-1000 °C, specifically it can be 450 °C, 500 °C, 600 °C, 700 °C, 800 °C, 900 °C, 1000 °C. The time of the calcination is preferably 0.1-10 h, specifically it can be 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, 10 h. After the above calcination, a vanadium-containing product is obtained, the main component of which is V2O5, and the content of V2O5 reaches more than 95%.

[0215] Regarding hydrolysis precipitation of vanadium:

[0216] The hydrolysis precipitation of vanadium includes: oxidizing the vanadium-chromium enriched solution with an oxidant, heating for reaction, filtering, and washing to obtain a chromium-containing filtrate and a vanadium-containing filter cake respectively.

[0217] When the present invention performs hydrolysis precipitation of vanadium, it is to precipitate pentavalent vanadium. Therefore, the vanadium-chromium enriched solution cannot be directly subjected to hydrolysis precipitation, but the vanadium-chromium enriched solution is pre-oxidized to oxidize the tetravalent vanadium therein into pentavalent vanadium. Among them, the oxidant is preferably at least one of hydrogen peroxide, chlorate, hypochlorite, and persulfate; among them, the concentration of the hydrogen peroxide is preferably 2%-30%, more preferably 30%. The dosage of the oxidant is preferably 1-3 times the reaction equivalent of oxidizing tetravalent vanadium into pentavalent vanadium, specifically it can be 1.5 times.

[0218] The temperature of the heating is 50 °C-110 °C, preferably 70 °C-110 °C, specifically it can be 70 °C, 80 °C, 90 °C, 100 °C, 110 °C, and more preferably heated to boiling. After heating to boiling, continue to maintain heating for 0.1-10 h, specifically it can be 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, 10 h. Stirring is preferably accompanied during the process of maintaining heating. During the above heating process, pentavalent vanadium in the vanadium-chromium enriched solution reacts to form a polyvanadic acid precipitate.

[0219] After the above heating reaction, filtration and washing are carried out. Among them, the washing is preferably water washing. The volume ratio of the water to the vanadium-chromium enriched solution is preferably (0-10):1 and not 0, specifically it can be 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1. After the above filtration and washing, a vanadium-containing filter cake and a chromium-containing filtrate are obtained respectively.

[0220] In the present invention, after obtaining the vanadium-containing filter cake, it is preferably further subjected to calcination treatment to obtain a vanadium-containing product. Among them, the temperature of the calcination is preferably 450-1000 °C, specifically 450 °C, 500 °C, 600 °C, 700 °C, 800 °C, 900 °C, 1000 °C. The time of the calcination is preferably 0.1-10 h, specifically 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, 10 h. After the above calcination, a vanadium-containing product is obtained, the main component of which is V2O5, and the content of V2O5 reaches more than 95%.

[0221] In the method provided by the present invention, in step (A), after the preliminary neutralization in step (A1) is completed, filtration is not carried out, and step (A2) secondary neutralization is directly carried out. This is for the case where the content of liquid vanadium or chromium in the system after neutralization is high (V2O5 content ≥ 0.5 g / L, or Cr2O3 content ≥ 0.5 g / L), in which it can be directly back-dissolved to obtain a high-concentration vanadium-chromium solution without multiple enrichments; or for the case where the free sulfuric acid in the titanium white waste acid is not high (free sulfuric acid < 100 g / L).

[0222] In the method provided by the present invention, after step (A1) is completed, steps (A2)-(A4) are not carried out, and step (B) is directly carried out; or steps (A2)-(B) are not carried out, and step (C) is directly carried out. That is, after the preliminary neutralization in step (A), secondary neutralization and back-dissolution for enriching titanium, vanadium and chromium are not carried out, and step (B) or (C) is directly carried out to separate titanium, vanadium and chromium. This is for the case where the content of titanium, vanadium or chromium in filtrate 1 is high (TiO2 content ≥ 1 g / L, V2O5 content ≥ 0.5 g / L, or Cr2O3 content ≥ 0.5 g / L).

[0223] In the method provided by the present invention, after the enrichment of titanium, vanadium and chromium in step (A2) is completed, steps (A4)-(D) are not carried out, and step (E-X) is directly carried out to separate vanadium and chromium. This is for the case where the content of vanadium or chromium in filter cake 2 is high (V2O5 content ≥ 1%, or Cr2O3 content ≥ 1%), and titanium is not hydrolyzed and recovered.

[0224] The present invention provides a method for enriching and separating titanium, vanadium, and chromium from titanium white waste acid. First, an alkaline substance containing calcium and / or magnesium is mixed with the titanium white waste acid for an acid-base neutralization reaction to reduce the acidity of the titanium white waste acid, obtaining a filtrate containing titanium, vanadium, and chromium. Then, the filtrate containing titanium, vanadium, and chromium is frozen, filtered, and washed to obtain ammonium aluminum sulfate crystals and a filtrate containing titanium, vanadium, and chromium respectively. Next, the filtrate containing titanium, vanadium, and chromium is diluted and hydrolyzed, and the pH value is adjusted to hydrolyze titanyl sulfate while the vanadium and chromium sulfates do not hydrolyze, separating to obtain metatitanic acid slurry and a diluted vanadium and chromium solution. After that, the diluted vanadium and chromium solution is neutralized and filtered to obtain a vanadium and chromium filter cake. Then, the vanadium and chromium filter cake is subjected to extraction and separation. One of the extraction and separation methods is the roasting and leaching method, and the second method is the acid dissolution and enrichment separation method. Through extraction and separation, chromium-containing products and vanadium-containing products are obtained respectively. The method of the present invention can gradually separate and recover these high-value substances such as titanium, chromium, and vanadium, solves the problem of their difficult separation and recovery, and improves the enrichment and separation efficiency, reducing the difficulty and cost of recovery and separation.

[0225] Compared with the prior art, the present invention has the following beneficial effects:

[0226] (1) The present invention adopts the method of neutralization precipitation and then acid reverse dissolution for the titanium, vanadium, and chromium-containing solution, enriching the relatively high-value titanium, vanadium, and chromium elements, which is beneficial to reducing the difficulty and cost of separating and extracting titanium, vanadium, and chromium elements later.

[0227] (2) The present invention hydrolyzes titanium by diluting and hydrolyzing (combining heating hydrolysis and dilution hydrolysis, or non-heating hydrolysis and dilution hydrolysis) the titanium, vanadium, and chromium-containing solution after reducing the acidity, obtaining a titanium-containing slurry with a relatively high titanium content and a vanadium and chromium solution with a very low titanium content. When separating vanadium and chromium from the vanadium and chromium solution, especially when using the extraction method to separate vanadium and chromium, there is basically no emulsification phenomenon, greatly reducing the consumption of the extractant and significantly shortening the extraction and stripping cycle. The role of the dilution water is, on the one hand, to promote the hydrolysis of titanyl sulfate into metatitanic acid, and on the other hand, to multiply dilute the content of vanadium and chromium in the settled metatitanic acid slurry and improve the recovery rate of vanadium and chromium. The addition amount of the dilution water can be adjusted according to the contents of vanadium, chromium, etc. in the titanium-containing slurry, and can be 0 to 10,000 times. If there are basically no impurities in the titanium-containing slurry that have a great impact on the quality of titanium white, or vanadium and chromium are not recovered, the amount of dilution water can be zero.

[0228] (3) The present invention adopts the method of neutralization precipitation and then acid reverse dissolution for the titanium, vanadium, and chromium-containing solution, which has two major advantages: ① A large amount of heat is generated during the neutralization reaction between steel slag powder and titanium white waste acid, resulting in the hydrolysis of titanyl sulfate and the like into colloids that are difficult to filter. If the acidity is reduced to allow these colloids to form precipitates, and then these precipitates are dissolved with sulfuric acid to form acid-soluble substances, the production problem of difficult filtration is solved; ② When the vanadium and chromium-containing filter cake after secondary neutralization is returned to the preliminary neutralization to dissolve titanium, vanadium, and chromium, and the titanium, vanadium, and chromium solution is returned as a titanium solution leaching agent, both can greatly increase the concentrations of titanium, vanadium, chromium, and aluminum, and create favorable conditions for aluminum removal, thereby improving the grade of chromium in the chromium slag.

[0229] (4) The present invention solves the problem of vanadium-chromium separation by means of oxidative roasting leaching, extractant extraction and back-extraction, resin adsorption and desorption, ammonium salt vanadium precipitation, and hydrolysis vanadium precipitation.

[0230] (5) The method of the present invention can simultaneously enrich and separate one or more of the three elements of titanium, vanadium, and chromium in titanium white waste acid, and can also recover one or more of the three elements according to their actual value.

[0231] (6) The present invention greatly improves the enrichment and separation efficiency, reduces the extraction difficulty and extraction cost, and significantly improves the production feasibility.

[0232] The test results show that the method of the present invention can successfully separate and recover titanium, chromium, and vanadium in titanium white waste acid, and obtain titanium-containing products, vanadium-containing products, and chromium-containing products respectively, solving the problem of difficult separation of titanium, vanadium, and chromium, especially the difficult separation of vanadium and chromium; moreover, the recovery rate of TiO2 in the titanium-containing product reaches more than 75% (excluding TiO2 in steel slag), the recovery rate of Cr2O3 in the chromium-containing product reaches more than 70%, and the recovery rate of V2O5 in the vanadium-containing product reaches more than 70%, realizing the efficient enrichment and separation of titanium, chromium, and vanadium, improving the enrichment and separation efficiency, and reducing the extraction difficulty and extraction cost.

[0233] To further understand the present invention, the preferred implementation schemes of the present invention will be described below in conjunction with embodiments. However, it should be understood that these descriptions are only for further explaining the features and advantages of the present invention, rather than limiting the claims of the present invention.

[0234] Example 1

[0235] The main components of the steel slag and titanium white waste acid used in this example are shown in Table 1.

[0236] Table 1 Main components of steel slag and titanium white waste acid

[0237] Component <![CDATA[V2O5]]> <![CDATA[Cr2O3]]> <![CDATA[Fe2O3]]> CaO MgO <![CDATA[SO3]]> <![CDATA[TiO2]]> <![CDATA[SiO2]]> MnO <![CDATA[P2O5]]> <![CDATA[Al2O3]]> Steel slag, % 2.33 0.45 27.04 35.02 3.67 6.2 3.59 9.6 3.5 1.56 2.2 Component <![CDATA[V2O5]]> <![CDATA[Cr2O3]]> Fe CaO Mg Free acid <![CDATA[TiO2]]> <![CDATA[SiO2]]> Mn P Al Waste acid, g / L 7.28 3.41 36.8 0.86 18.03 286.7 6.84 0.10 2.4 0.06 8.45

[0238] (A) Enriching titanium, vanadium, and chromium:

[0239] (A1) Take 6000 g of steel slag powder, add it to 27.5 L of titanium white waste acid, stir for 2 h, the pH value is 1.1, then filter, and wash with 9 L of water to obtain 15568.79 g of wet filter cake 1 and 30.40 L of filtrate 1 respectively.

[0240] (A2) Stir and mix all 30.40 L of the filtrate with 4000 g of steel slag powder for 4 h, the pH value is 4.4, then filter, and wash with 15 L of water to obtain 14637.23 g of wet filter cake 2 and 35.10 L of filtrate 2. In filtrate 2: TiO2 < 0.01 g / L, V2O5 < 0.01 g / L, Cr2O3 < 0.01 g / L.

[0241] (A3) Judgment: The enriched content of titanium, vanadium, and chromium in the filter cake 2 meets the standard, and directly proceed to step (A4).

[0242] (A4) Pulp all 14637.23 g of wet filter cake 2 with 1500 g of concentrated sulfuric acid. After pulping for 2 h, the pH value is 0.8. Then, filter and wash with 18 L of water to obtain 10379.20 g of wet filter cake 3 and 23.020 L of titanium, vanadium, and chromium-containing filtrate 3 respectively.

[0243] The filter cake 1 and filter cake 3 are dried and mixed evenly to obtain a total of 13729.59 g of dried filter cake. In the dried filter cake: TiO2 is 2.80%, V2O5 is 0.24%, and Cr2O3 is 0.08%.

[0244] In the titanium, vanadium, and chromium-containing filtrate 3: TiO2 is 7.07 g / L, V2O5 is 17.38 g / L, and Cr2O3 is 5.55 g / L; the liquid-based yields are 29.73%, 92.39%, and 92.09% respectively.

[0245] (B) Add 820 g of ammonium sulfate to the filtrate 3 and freeze it to 1 °C, then filter and wash with 2.5 L of water to obtain 5490.58 g of ammonium aluminum sulfate dodecahydrate crystals and 20.61 L of filtrate 4 respectively.

[0246] In the filtrate 4: TiO2 is 7.75 g / L, V2O5 is 19.07 g / L, and Cr2O3 is 6.09 g / L; the liquid-based yields are 98.14%, 98.19%, and 98.21% respectively.

[0247] (C) Dilution and hydrolysis:

[0248] (C1) Add 250 g of magnesium hydroxide to the filtrate 4 to adjust the pH to 2.0, then heat to 90 °C in 30 min, dilute with water to 200 L, carry out dilution and hydrolysis for 1 h, let it stand for 5 h, and separate to obtain 190 L of upper-layer vanadium and chromium-containing solution and 10 L of lower-layer titanium-containing slurry respectively;

[0249] (C2) Further dilution process: Continuously dilute the 10 L of lower-layer titanium-containing slurry obtained in step (C1) with water to 100 L, add 20 g of sulfuric acid to adjust the pH to 3.16, let it stand for 5 h, and separate to obtain 90 L of further-diluted upper-layer vanadium and chromium-containing solution and 10 L of further-diluted lower-layer titanium-containing slurry respectively;

[0250] (C3) Combine the two upper-layer vanadium and chromium-containing solutions to finally obtain 280 L of vanadium and chromium-containing solution and 10 L of lower-layer titanium-containing slurry;

[0251] In the vanadium and chromium-containing solution: TiO2 is 0.01 g / L, V2O5 is 1.39 g / L, and Cr2O3 is 0.44 g / L; the yields are 1.70%, 99.00%, and 99.00% respectively;

[0252] In the lower titanium-containing slurry: TiO2 is 16.48 g / L, V2O5 is 0.39 g / L, Cr2O3 is 0.13 g / L, and the yields are 98.30%, 1.00%, and 1.00% respectively.

[0253] (D) Add 618 g of magnesium hydroxide to the 280 L of vanadium- and chromium-containing solution obtained in step (C) to adjust the pH to 5.40, filter, and wash with 5 L of water to obtain 5488 g of vanadium- and chromium-containing filter cake 3 and 280 L of filtrate 4 respectively. In filtrate 4: V2O5 < 0.01 g / L, Cr2O3 < 0.01 g / L.

[0254] (E-X) Calcination roasting leaching:

[0255] E-X1: Take 1488 g of vanadium- and chromium-containing filter cake 3, dry it at 100 °C to obtain 187.48 g of vanadium- and chromium-containing slag. In the vanadium- and chromium-containing slag: V2O5 is 48.44%, Cr2O3 is 15.47%.

[0256] E-X2: Take 50 g of vanadium- and chromium-containing slag, add 8 g of calcium oxide, grind and mix evenly, then roast at 980 °C for 30 min to obtain 48.97 g of clinker, and grind it to -200 mesh.

[0257] E-X3: Add the clinker to 400 mL of water, then add 16 g of sulfuric acid for leaching, keep the pH value between 1 and 3 for 3 h, filter and wash to obtain 39.61 g of chromium-containing slag and 1.0 L of vanadium-containing solution respectively.

[0258] In the chromium-containing slag: V2O5 is 5.45%, Cr2O3 is 18.93%, and the yields based on the slag are 8.92% and 96.96% respectively;

[0259] In the vanadium-containing solution: V2O5 is 22.06 g / L, Cr2O3 is 0.235 g / L, and the yields based on the solution are 91.08% and 3.04% respectively.

[0260] Example 2

[0261] (E-X) Magnesium roasting leaching:

[0262] E-X2: Take 50 g of vanadium- and chromium-containing slag from the vanadium- and chromium-containing slag obtained in step E-X1 of Example 1, add 8 g of magnesium hydroxide, grind and mix evenly, then roast at 900 °C for 4 h to obtain 46.53 g of clinker, and grind it to -200 mesh.

[0263] E-X3: Add the clinker to 400 mL of water, then add 16 g of sulfuric acid for leaching, keep the pH value between 1 and 3 for 6 h, filter and wash to obtain 19.21 g of chromium-containing slag and 1.0 L of vanadium-containing solution respectively.

[0264] In the chromium-containing slag: V2O5 is 14.89%, Cr2O3 is 38.26%, and the recovery rates based on the slag are 11.81% and 95.02% respectively;

[0265] In the vanadium-containing solution: V2O5 is 21.36 g / L, Cr2O3 is 0.385 g / L, and the recovery rates based on the solution are 88.19% and 4.98% respectively.

[0266] Example 3

[0267] (E-X) Sodium roasting and leaching:

[0268] E-X2: Take 50 g of vanadium- and chromium-containing slag obtained from step E-X1 of Example 1, add 17 g of sodium carbonate, grind and mix evenly, then roast at 800 °C for 2 h to obtain 47.45 g of clinker, and grind it to -200 mesh.

[0269] E-X3: Add the clinker to 400 mL of water and leach for 2 h, with a pH value of 9.2. Filter and wash to obtain 18.56 g of chromium-containing slag and 1.0 L of vanadium-containing solution respectively.

[0270] In the chromium-containing slag: V2O5 is 9.48%, Cr2O3 is 38.25%, and the recovery rates based on the slag are 7.27% and 91.79% respectively;

[0271] In the vanadium-containing solution: V2O5 is 22.46 g / L, Cr2O3 is 0.635 g / L, and the recovery rates based on the solution are 92.73% and 8.21% respectively.

[0272] Example 4

[0273] (E-Y) Acid dissolution, enrichment and separation:

[0274] E-Y1: Dissolve 4000 g of the vanadium- and chromium-containing filter cake 3 obtained from step (D) of Example 1 with 724 g of concentrated sulfuric acid to obtain 4.29 L of vanadium- and chromium-enriched solution 7 with a pH of 1.74. In the vanadium- and chromium-enriched solution 7: V2O5 is 66.03 g / L, Cr2O3 is 21.09 g / L.

[0275] E-Y2: Extract tetravalent vanadium with a phosphoric acid-based extractant:

[0276] Take 100 mL of the vanadium- and chromium-enriched solution 7, mix it with a P204 extractant mixture (20% P204 + 5% TBP + 75% solvent oil 260#), carry out 5-stage extraction, with 200 mL of the extractant mixture used for each stage, an O / A ratio of 2:1, and an extraction pH value of 1.2 to obtain an extraction phase and a raffinate respectively; then carry out countercurrent stripping of the extraction phase with 200 mL of a 20% sulfuric acid solution to obtain a stripping solution.

[0277] In the raffinate: V2O5 is 0.48 g / L, Cr2O3 is 20.58 g / L, and the extraction rates are 99.28% and 2.41% respectively;

[0278] In the stripping solution: V2O5 is 31.87 g / L, Cr2O3 is 0.16 g / L, and the stripping rates are 97.23% and 62.38% respectively.

[0279] Example 5

[0280] E-Y2: Extraction of pentavalent vanadium with amine extractant:

[0281] Take 100 mL from the vanadium-chromium enriched solution 7 obtained in step E-Y1 of Example 4, oxidize tetravalent vanadium to pentavalent vanadium with 15 mL of 30% hydrogen peroxide, mix with N235 extractant mixture (20% N235 + 5% TBP + 75% solvent oil 260#), perform 5-stage extraction, use 218 mL of extractant mixture for each stage of extraction, O / A ratio is 2:1, extraction pH value is 2.0, and obtain the extraction phase and raffinate respectively; then perform countercurrent stripping with 200 mL of 10% sodium hydroxide solution to obtain the stripping solution.

[0282] In the raffinate: V2O5 is 0.41 g / L, Cr2O3 is 19.34 g / L, and the extraction rates are 99.32% and 0.05% respectively;

[0283] In the stripping solution: V2O5 is 32.23 g / L, Cr2O3 < 0.01 g / L, and the stripping rates are 97.23% and 0% respectively.

[0284] Example 6

[0285] E-Y2: Cation resin exchange adsorption of vanadium:

[0286] Take 40 mL from the vanadium-chromium enriched solution 7 obtained in step E-Y1 of Example 4 and dilute it to 100 mL, add 50 g of Duolite CH-93 cationic resin and soak, stir for 24 h, adsorption pH value is 2.0, and obtain the resin after adsorption and the adsorption residue solution respectively. Under the control of the flow rate of the peristaltic pump, desorb with 50 mL of 20% sulfuric acid solution and wash with 50 mL of water for 4 h to obtain 100 mL of desorbing solution.

[0287] In the adsorption residue solution: V2O5 is 2.43 g / L, Cr2O3 is 7.49 g / L, and the resin adsorption rates are 90.80% and 11.21% respectively;

[0288] In the desorbing solution: V2O5 is 23.98 g / L, Cr2O3 is 19.57 g / L, and the desorption rates are 96.42% and 95.22% respectively.

[0289] Example 7

[0290] E-Y2: Anion resin exchange adsorption of pentavalent vanadium:

[0291] Take 100 mL from the vanadium-chromium enriched solution 7 obtained in step E-Y1 of Example 4. Use 15 mL of 30% hydrogen peroxide to oxidize tetravalent vanadium to pentavalent vanadium. Add 100 g of Rohm and Haas IRA96rf anion resin and soak, stir for 24 h, with an adsorption pH value of 2.0, to obtain the adsorbed resin and the adsorption residue solution respectively. Use 150 mL of 10% sodium hydroxide solution and 50 mL of water to desorb for 4 h to obtain 200 mL of desorbing solution.

[0292] In the adsorption residue solution: V2O5 is 0.20 g / L, Cr2O3 is 18.88 g / L, and the resin adsorption rates are 99.67% and 2.43% respectively;

[0293] In the desorbing solution: V2O5 is 32.30 g / L, Cr2O3 is 0.06 g / L, and the desorption rates are 98.15% and 25.29% respectively.

[0294] Example 8

[0295] E-Y2: Ammonium salt precipitation of vanadium

[0296] Take 500 mL from the vanadium-chromium enriched solution obtained in step E-Y1 of Example 4. Use 80 mL of 30% hydrogen peroxide to oxidize tetravalent vanadium to pentavalent vanadium. Add 60 g of ammonium sulfate, heat to boiling, continue stirring and heating for 2 h, filter, and wash with about 1500 mL of water to obtain 1550 mL of chromium-containing filtrate and 298.12 g of vanadium-containing filter cake (wet filter cake) respectively. Calcinate the vanadium-containing filter cake at 500 °C for 1 h to obtain 33.53 g of vanadium product.

[0297] In the chromium-containing filtrate: V2O5 is 0.28 g / L, Cr2O3 is 6.52 g / L, and the yields are 1.31% and 92.88% respectively;

[0298] In the vanadium product: V2O5 is 97.18%, Cr2O3 is 2.24%, and the yields are 98.69% and 7.12% respectively.

[0299] Example 9

[0300] E-Y2: Hydrolysis precipitation of vanadium

[0301] Take 500 mL from the vanadium-chromium enriched solution obtained in step E-Y1 of Example 4. Use 80 mL of 30% hydrogen peroxide to oxidize tetravalent vanadium to pentavalent vanadium. Heat to boiling, continue stirring and heating for 2 h, filter, and wash with about 1500 mL of water to obtain 1600 mL of chromium-containing filtrate and 206.89 g of vanadium-containing filter cake (wet filter cake) respectively. Calcinate the vanadium-containing filter cake at 500 °C for 1 h to obtain 32.55 g of vanadium product.

[0302] In the chromium-containing filtrate: V2O5 is 0.64 g / L, Cr2O3 is 6.31 g / L, and the yields are 3.10% and 95.73% respectively;

[0303] In the vanadium product: V2O5 is 98.27%, Cr2O3 is 1.38%, and the yields are 96.90% and 4.27% respectively.

[0304] Example 10 (high vanadium concentration, directly separated after preliminary neutralization)

[0305] 165 g of lime powder was added to 1000 ml of No. 2 titanium white waste acid with stirring for 1 h, and after continuous stirring for 0.5 h, the pH was 1.94. Filtration was started and washed with 400 mL of water to obtain 484.66 g of dried filter cake at 100 °C. In the filter cake, TiO2 is 0.09%, V2O5 is 0.15%, and Cr2O3 is 0.01%; 1050 mL of filtrate A was obtained, with TiO2 being 6.67 g / L, V2O5 being 15.81 g / L, and Cr2O3 being 0.609 g / L. The liquid-based yields are 94.15%, 95.81%, and 92.98% respectively. 525 ml of filtrate A was diluted with water to 5000 mL, and hydrolyzed by dilution at room temperature. After 15 h of separation, 4800 mL of supernatant and 200 mL of lower slurry were obtained. In the supernatant, TiO2 is 0.044 g / L, V2O5 is 1.64 g / L, and Cr2O3 is 0.062 g / L, and the yields are 6.01%, 96.58%, and 95.22% respectively; in the lower slurry, TiO2 is 16.48 g / L, V2O5 is 1.90 g / L, and Cr2O3 is 0.077 g / L, and the yields are 93.99%, 3.42%, and 4.78% respectively. (Vanadium-titanium separation was achieved. Since the chromium concentration is much lower than that of vanadium, vanadium-chromium separation is not required.)

[0306] Example 11 (high vanadium concentration in filtrate 1, after the secondary neutralization step, directly extract vanadium by the E-X method without recovering titanium)

[0307] Take 500 ml of filtrate A from Example 10 and neutralize it to pH 4.48 with 100 g of steel slag powder, filter and wash to obtain 800 mL of filtrate and 365.23 g of wet filter cake. In the filtrate, TiO2 is <0.01 g / L, V2O5 is <0.01 g / L, and Cr2O3 is <0.01 g / L; the wet filter cake was calcined at 1000 °C for 1 h and then weighed 126.75 g. It was ground to -200 mesh and leached with 20% sulfuric acid to maintain pH 2.5 - 3.0. After drying the leaching residue, it weighed 117.91 g. In the residue, V2O5 is 1.08% and Cr2O3 is 0.59%, and the leaching conversion rates are 87.56% and 7.8% respectively. (Without recovering titanium, the vanadium extraction steps are simplified)

[0308] As can be seen from the above embodiments, the method of the present invention can successfully separate and recover titanium, chromium, and vanadium in titanium white waste acid to obtain titanium-containing products, vanadium-containing products, and chromium-containing products respectively, solving the problem of difficult separation of titanium, vanadium, and chromium, especially the difficult separation of vanadium and chromium. Moreover, the recovery rate of TiO2 in the titanium-containing product reaches more than 75%, the recovery rate of Cr2O3 in the chromium-containing product reaches more than 70%, and the recovery rate of V2O5 in the vanadium-containing product reaches more than 70%, realizing the efficient enrichment and separation of titanium, chromium, and vanadium, improving the enrichment and separation efficiency, and reducing the extraction difficulty and extraction cost.

[0309] In this article, specific examples are used to elaborate on the principle and implementation mode of the present invention. The description of the above embodiments is only used to help understand the method and its core idea of the present invention, including the best mode, and also enables any person skilled in the art to practice the present invention, including manufacturing and using any device or system, and implementing any combined method. It should be noted that for those of ordinary skill in the art in this technical field, without departing from the principle of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention. The protection scope of the present invention patent is defined by the claims and may include other embodiments that can be conceived by those skilled in the art. If these other embodiments have structural elements similar to the literal description of the claims, or if they include equivalent structural elements that have no substantial difference from the literal description of the claims, then these other embodiments should also be included within the scope of the claims.

Claims

1. A method for enriching and separating titanium, vanadium and chromium from titanium dioxide waste acid, characterized in that: The following steps are involved: (A) mixing an alkaline substance with titanium dioxide waste acid to carry out an acid-base reaction to enrich titanium, vanadium and chromium; The enrichment comprises the following steps: (A1) mixing an alkaline substance with titanium dioxide waste acid to perform a preliminary acid-base neutralization reaction, and then filtering and washing to obtain a filter cake 1 and a filtrate 1, respectively; (A2) mixing an alkaline substance with the filtrate 1 to perform an acid-base secondary neutralization reaction, and then filtering and washing to obtain a titanium, vanadium and chromium-containing filter cake 2 and a filtrate 2; (A3) Determination: Determine the titanium, vanadium and chromium enrichment content in the filter cake 2. If it is qualified, proceed to step (A4); if it is unqualified, return the filter cake 2 to step (A1) to react with the titanium dioxide waste acid to cyclically enrich the titanium, vanadium and chromium until the titanium, vanadium and chromium enrichment content in the filter cake 2 is qualified, and then proceed to step (A4); The qualified standards are: TiO2 content in dry basis ≥ 0.5%, or V2O5 content in dry basis ≥ 0.1%, or Cr2O3 content in dry basis ≥ 0.1%; (A4) mixing the titanium, vanadium and chromium-containing filter cake 2 with an acid solution, slurrying the mixture, filtering the mixture and washing the mixture to obtain a filter cake 3 and a titanium, vanadium and chromium-containing filtrate 3; (B) adding ammonia or ammonium to the filtrate 3, freezing, filtering, and washing to obtain aluminum ammonium sulfate crystals 4 and filtrate 4, respectively; (C) diluting and hydrolyzing the filtrate 4, and separating to obtain an upper layer of a vanadium-chromium-containing solution 5 and a lower layer of a titanium-containing slurry 5; (D) adding an alkaline substance to neutralize the upper vanadium-chromium solution 5, and then filtering and washing to obtain a vanadium-chromium filter cake 6 and a filtrate 6, respectively; (E) extracting and separating the vanadium-chromium filter cake 6 to obtain a chromium-containing product and a vanadium-containing product respectively; The extraction and separation method is method EX or method EY: The method EX comprises the following steps: E-X1: drying the vanadium-chromium-containing filter cake 6 to obtain vanadium-chromium-containing slag; E-X2: roasting the vanadium-chromium slag to obtain clinker; or, mixing the vanadium-chromium slag with an oxidant, roasting, to obtain clinker; E-X3: leaching the clinker, separating the solid and the liquid, and obtaining chromium-containing slag and vanadium-containing liquid respectively; The method EY comprises the following steps: E-Y1: dissolving the vanadium-chromium-containing filter cake 6 with sulfuric acid to obtain a vanadium-chromium-enriched solution 7; E-Y2: Separate and extract the vanadium-chromium enriched liquid 7 to obtain a vanadium-containing product and a chromium-containing liquid, respectively.

2. The method according to claim 1, characterized in that In step (A1): The alkaline substance is an alkaline substance containing calcium and / or magnesium; The amount of the alkaline substance is such that the pH value of the system after the initial acid-base neutralization reaction reaches: 0.5 < pH < 3.0; preferably 0.8 < pH < 1.5; In step (A2): The alkaline substance is an alkaline substance containing calcium and / or magnesium; The amount of the alkaline substance is such that the pH value of the system after the secondary neutralization reaction of acid and base reaches: 3.0<pH<8.0; preferably 4<pH<6.0; In step (A4): The acid solution is sulfuric acid solution and / or titanium dioxide waste acid; The amount of the acid solution is such that the pH value of the system reaches: 0<pH<3.5; preferably 0.5<pH<1.5; more preferably 0.8<pH<1.5; In step (D): The amount of the alkaline substance used is such that the pH value of the system reaches: 3.5<pH<8; preferably 4<pH<8.

3. The method according to claim 1 or 2, characterized in that: In step (A1), the alkaline substance is at least one of calcium carbonate, calcium oxide, calcium hydroxide, magnesium oxide, magnesium carbonate, magnesium hydroxide, steel slag, and blast furnace slag; In step (A2), the alkaline substance is at least one of calcium carbonate, calcium oxide, calcium hydroxide, magnesium oxide, magnesium carbonate, magnesium hydroxide, steel slag, and blast furnace slag; In step (D), the alkaline substance is at least one of sodium hydroxide, sodium carbonate, ammonia water, calcium carbonate, calcium oxide, calcium hydroxide, magnesium oxide, magnesium carbonate, magnesium hydroxide, steel slag, and blast furnace slag; In step (B), the freezing temperature is 0-10°C.

4. The method according to claim 1, characterized in that: Step (C) specifically comprises: (C1) adding alkaline substances to the filtrate 4 to adjust the pH value, then adding water to dilute and hydrolyze, and then separating to obtain an upper layer of vanadium-chromium-containing solution and a lower layer of titanium-containing slurry; (C2) Re-dilution treatment: The lower titanium-containing slurry is used as the initial treatment object, and a re-dilution process is performed N times; Each re-dilution process includes: diluting the titanium-containing slurry with water, adding acid to adjust the pH value, standing and separating, and obtaining a re-diluted upper layer of vanadium-chromium-containing solution and a re-diluted lower layer of titanium-containing slurry; In each redilution process, the rediluted lower titanium-containing slurry obtained in the previous redilution process is the processing object; N is an integer ≥ 0; (C3) All upper vanadium-chromium-containing solutions obtained in steps (C1) to (C2) are combined to obtain a vanadium-chromium-containing solution 5.

5. The method according to claim 4, characterized in that In step (C1): The pH value is adjusted to 1 to 4, preferably 2.5 to 3.5; The dilution and hydrolysis temperature is 0 to 110°C; In step (C2): N is 0, 1, 2, 3, 4 or 5; The pH value is adjusted to 1-4, preferably 2.5-3.

5.

6. The method according to claim 1, characterized in that In step E-X2: The co-oxidant is preferably a calcium co-oxidant, a magnesium co-oxidant or a sodium co-oxidant; wherein the calcium co-oxidant is calcium oxide; the magnesium co-oxidant is magnesium oxide and / or magnesium hydroxide; the sodium co-oxidant is sodium carbonate; The mass ratio of the pro-oxidant to the vanadium-chromium slag is (0-50):50 and is not 0; The calcination temperature is 750-1100°C; The calcination time is 20 to 300 minutes; In step E-Y2, the separation and extraction method is extraction stripping, adsorption desorption, ammonium salt precipitation of vanadium or hydrolysis precipitation of vanadium.

7. The method according to claim 1 or 6, characterized in that: In step E-X2: The pro-oxidant is a calcium pro-oxidant, the mass ratio of the calcium pro-oxidant to the vanadium-chromium slag is (0-50):50 and is not 0, the roasting temperature is 850-1100° C., and the roasting time is 20-300 min; Or, the pro-oxidant is a magnesium pro-oxidant, the mass ratio of the magnesium pro-oxidant to the vanadium-chromium-containing slag is (0-50):50 and is not 0, the calcination temperature is 850-1100° C., and the calcination time is 20-300 min; Or, the pro-oxidant is a sodium pro-oxidant, the mass ratio of the sodium pro-oxidant to the vanadium-chromium-containing slag is (0-50):50 and is not 0, the roasting temperature is 750-900°C, and the roasting time is 20-300min.

8. The method according to claim 6, characterized in that The extraction and stripping comprises: contacting the vanadium-chromium-rich solution 7 with an extractant for extraction, and then stripping to obtain a vanadium-containing solution and a chromium-containing solution respectively; Wherein, the extractant is at least one of a phosphoric acid extractant and an amine extractant; wherein, the phosphoric acid extractant is at least one of a P204 extractant and a P507 extractant; wherein, the amine extractant is at least one of a N235 extractant and a N1923 extractant; When the extractant is an amine extractant, the vanadium-chromium enriched solution 7 is oxidized in advance to oxidize the tetravalent vanadium therein into pentavalent vanadium, and then the extraction is performed; The adsorption and desorption process comprises: contacting the vanadium-chromium-enriched liquid 7 with a cationic resin for resin adsorption, and then desorbing the solution to obtain a vanadium-containing liquid and a chromium-containing liquid respectively; or comprises: pre-oxidizing the tetravalent vanadium in the vanadium-chromium-enriched liquid 7 into pentavalent vanadium, contacting the solution with an anionic resin for resin adsorption, and then desorbing the solution to obtain a vanadium-containing liquid and a chromium-containing liquid respectively; Wherein, the anionic resin is at least one of Rohm and Haas IRA96rf anionic resin and D301 anionic resin; the cationic resin is at least one of Dusheng CH-91 cationic resin and Dusheng CH-93 cationic resin; The ammonium salt precipitation of vanadium comprises: oxidizing the vanadium-chromium enriched solution 7 with an oxidant, then adding ammonium sulfate, heating for reaction, filtering, and washing to obtain a chromium-containing filtrate and a vanadium-containing filter cake respectively; The hydrolysis and precipitation of vanadium comprises: oxidizing the vanadium-chromium enriched solution with an oxidant, heating for reaction, filtering, and washing to obtain a chromium-containing filtrate and a vanadium-containing filter cake, respectively.

9. The method according to claim 8, characterized in that In the extraction and stripping: Using an extractant mixed solution; the extractant mixed solution is a mixture of an extractant, TBP and solvent oil; In the adsorption and desorption: When the adsorption resin is a cationic resin, the desorption comprises sequentially desorbing with a sulfuric acid solution and eluting with water; When the adsorption resin is an anionic resin, the desorption comprises sequentially desorbing with a sodium hydroxide solution or an ammonia solution and eluting with water; In the ammonium salt vanadium precipitation: The weight ratio of the ammonium sulfate to the vanadium pentoxide in the vanadium-chromium enriched solution 7 is (0-10):1 and is not zero; The ammonium salt precipitation time is 0.1h to 100h; In the hydrolysis vanadium precipitation: The hydrolysis of vanadium precipitation is carried out by heating hydrolysis, and the hydrolysis temperature is 50°C to 110°C; The hydrolysis vanadium precipitation time is 0.1h to 100h.

10. The method according to claim 1, characterized in that In step (A), after the primary neutralization in step (A1), the secondary neutralization in step (A2) is directly performed without filtering; Alternatively, in step (A), after step (A1), steps (A2) to (A3) are not performed, but step (B) is performed directly; or steps (A2) to (B) are not performed, but step (C) is performed directly; Alternatively, in step (A), after step (A2) is completed, the obtained titanium, vanadium and chromium-containing filter cake 2 is not subjected to steps (A3) to (D), but directly subjected to step (EX) for separating vanadium and chromium.

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