Process for preparing high-purity vanadium pentoxide based on chloride process titanium dioxide waste acid in ammonium-free manner

Abstract

The invention provides an ammonium-free process for preparing high-purity vanadium pentoxide from titanium white waste acid based on a chlorination process, which comprises the following steps: pretreatment: removing suspended matters and hydrolysates of titanium and zirconium impurities; primary vanadium extraction and counter-current vanadium extraction; primary reverse extraction of vanadium: performing reverse extraction by using hydrochloric acid to obtain primary reverse vanadium liquid; primary impurity removal: extracting the primary anti-vanadium liquid to remove iron; carrying out secondary impurity removal, adding caustic soda liquid into the material liquid after iron removal to adjust the acidity, and carrying out counter-current extraction on yttrium; secondary vanadium extraction: extracting vanadium from the material liquid subjected to secondary impurity removal; carrying out secondary reverse extraction on vanadium, and carrying out countercurrent reverse extraction by using hydrochloric acid; removing oil; drying to obtain a VOCl2 solid; and roasting: roasting the VOCl2 solid, and decomposing the VOCl2 solid into V2O5. According to the ammonium-free process for preparing the high-purity vanadium pentoxide, the purity of the prepared vanadium pentoxide is high, the yield is high, the technological process is simple and efficient, introduction of ammonium salt is completely avoided in the whole process, no ammonium-containing wastewater is generated, and environmental friendliness is high.

Description

Technical Field

[0001] The present invention relates to the technical field of hydrometallurgy and resource recovery, and more specifically, to a process for preparing high-purity vanadium pentoxide without ammonium based on waste acid from titanium dioxide production by the chlorination method. Background Art

[0002] Vanadium is an important strategic metal. Due to its excellent physical and chemical properties such as high hardness, oxidation resistance, fatigue resistance, and characteristics of multivalent redox reactions, it is widely used in fields such as steel, chemical industry, aerospace, military industry, and new energy. Vanadium has multiple variable adjacent valence states from +2 to +5. Vanadium with an oxidation number of +5 has oxidizing properties, and vanadium with a low oxidation number has reducing properties. Vanadium pentoxide (V2O5) is the most common and commonly used form of vanadium. V2O5 with a purity of 98% is the current mainstream industrial-grade vanadium product.

[0003] High-purity V2O5 refers to V2O5 products with a purity above 99%. It is mainly used in all-vanadium redox flow batteries, aerospace-grade vanadium-aluminum alloys, vanadium-based catalysts, and the preparation of metallic vanadium. It is a key raw material that has gradually emerged with the development of strategic emerging industries such as new energy and aerospace. In recent years, its usage in related fields has shown a linear upward trend. With the continuous expansion of the application of vanadium in various industries, the purity requirements for V2O5 products have become increasingly strict.

[0004] Currently, methods for producing high-purity V2O5 include ammonium salt precipitation method, solvent extraction method, ion exchange method, etc. Among them, the ammonium salt precipitation process is a method used in most current vanadium extraction processes. However, the ammonium salt precipitation process needs to introduce ammonium ions, which will cause ammonia-nitrogen pollution and the subsequent treatment is complex. Although the existing solvent extraction method can separate vanadium, it has problems such as high impurity residue, cumbersome process, and low vanadium recovery rate. The waste acid from titanium dioxide production by the chlorination method is rich in vanadium elements, but contains impurities such as iron, aluminum, titanium, sodium, magnesium, silicon, and yttrium. Therefore, it is urgent to develop an efficient and environmentally friendly ammonium-free vanadium extraction process.

[0005] In view of this, the present invention is specifically proposed. Summary of the Invention

[0006] The object of the present invention is to overcome the deficiencies of the prior art and provide a process for preparing high-purity vanadium pentoxide without ammonium based on waste acid from titanium dioxide production by the chlorination method. The prepared vanadium pentoxide has high purity and high yield, the process flow is simple and efficient, the introduction of ammonium salts is completely avoided throughout the process, no ammonium-containing wastewater is generated, and it has strong environmental friendliness.

[0007] To achieve the above object of the present invention, the following technical solutions are specifically adopted:

[0008] A process for preparing high-purity vanadium pentoxide without ammonium based on waste acid from titanium dioxide production by the chlorination method, comprising the following steps:

[0009] Step S1, Pretreatment: Adjust the pH value of the waste acid from chloride process titanium dioxide using lye, and then add a flocculant to filter out suspended solids and hydrolysis products of titanium and zirconium impurities.

[0010] Step S2, First vanadium extraction: Extract vanadium from the pretreated waste acid from chloride process titanium dioxide by countercurrent extraction.

[0011] Step S3, First vanadium stripping: Use hydrochloric acid to strip the loaded organic phase after vanadium extraction to obtain the first stripped vanadium solution.

[0012] Step S4, First impurity removal: Remove iron from the first stripped vanadium solution by extraction.

[0013] Step S5, Second impurity removal: Adjust the acidity of the solution after iron removal by adding liquid caustic soda, and extract yttrium by countercurrent extraction.

[0014] Step S6, Second vanadium extraction: Extract vanadium from the solution after the second impurity removal.

[0015] Step S7, Second vanadium stripping: Use hydrochloric acid to strip the loaded organic phase after the second vanadium extraction by countercurrent stripping.

[0016] Step S8, Oil removal: Remove oil from the second stripped vanadium solution through an oil removal resin.

[0017] Step S9, Drying: Heat and evaporate the second stripped vanadium solution after oil removal to dryness to obtain VOCl2 solid.

[0018] Step S10, Roasting: Roast the VOCl2 solid to decompose it into V2O5.

[0019] Further, in Step S1, adjust the pH value of the waste acid from chloride process titanium dioxide to 0.6 - 1, adjust the temperature to 50 - 60 °C, add a flocculant and stir at a speed of 30 - 50 r / min for 5 - 10 min.

[0020] Further, the flocculant is one of polyacrylamide, polyaluminium chloride, and cationic polyacrylamide, and the dosage of the flocculant is 10 - 20 ppm.

[0021] Further, in Step S2, use 25% P204 + 5% TBP + 70% sulfonated kerosene (by volume) as the extractant, O / A = 1:3 - 5, and extract vanadium by countercurrent extraction for 6 - 10 stages.

[0022] Further, in Step S3, use 3 - 4 mol / L hydrochloric acid for the loaded organic phase after vanadium extraction, and strip it for 6 - 9 stages to obtain the first stripped vanadium solution.

[0023] Further, in step S4, first, 20% N235 + 5% isooctanol + 75% kerosene (by volume) is acidified. The acidifying water is 3.0 - 4.0N hydrochloric acid, and the acidification phase ratio O / A = 1 - 3:1. After acidification, the primary vanadium-containing liquid is subjected to iron extraction. The extraction phase ratio O / A = 1:6 - 8, and 1 - 3 stages of extraction are carried out.

[0024] Further, in step S5, after iron removal, the liquid material is added with liquid caustic to adjust the acidity to 1.0 - 1.5N. Using 25% P204 + 5% TBP + 70% sulfonated kerosene, according to the phase ratio O / A = 2 - 4:1, yttrium is extracted by 12 - 15 stages of countercurrent extraction, and continuously operated until the yttrium content in the outlet liquid material is less than 7 ppm; the loaded organic phase and hydrochloric acid with pH 1.0 - 2.0 are subjected to 3 - 5 stages of countercurrent washing according to the phase ratio O / A = 2 - 4:1.

[0025] Further, in step S6, the pH of the liquid material after secondary impurity removal is adjusted to 0.6 - 1. Using 25% P204 + 5% TBP + 70% sulfonated kerosene (by volume), according to the phase ratio O / A = 2 - 4:1, vanadium is extracted to further separate impurities such as aluminum, calcium, magnesium, silicon, sodium, and manganese; the loaded organic phase and hydrochloric acid with pH 1.0 - 2.0 are subjected to 3 - 5 stages of countercurrent washing according to the phase ratio O / A = 2 - 4:1.

[0026] Further, in step S7, the loaded organic phase is stripped with 5 - 6M hydrochloric acid, according to the phase ratio O / A = 3 - 5:1, and multi-stage countercurrent stripping is adopted until the concentration of the secondary vanadium-containing liquid at the outlet is greater than 160 g / L.

[0027] Further, this process also includes step S11, tail gas recovery: The roasting tail gas is chlorine gas, which is returned to the titanium dioxide production system by chlorination method after washing, cooling, and drying treatment.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0029] 1. The process for preparing high-purity vanadium pentoxide of the present invention uses the waste acid from titanium dioxide production by chlorination method as raw material. Through multi-stage extraction, stripping, crystallization, and high-temperature roasting processes, the obtained vanadium pentoxide has high purity and high yield, and the preparation process flow is simple and efficient; and the entire process flow completely avoids the introduction of ammonium salts, no ammonium-containing wastewater is generated, and no ammonia nitrogen pollution will be caused, and it has strong environmental friendliness.

[0030] 2. The process for preparing high-purity vanadium pentoxide of the present invention uses a multi-stage extraction and impurity removal process to extract vanadium from the waste acid of titanium dioxide production by chlorination method. The purity of the obtained V2O5 ≥ 99.92%, and the vanadium recovery rate ≥ 99.2%.

[0031] 3. The process for preparing high-purity vanadium pentoxide in the present invention comprehensively separates and removes impurity elements in the waste acid from chloride process titanium dioxide, which can effectively reduce the contents of impurity elements such as iron, aluminum, titanium, sodium, magnesium, silicon, yttrium, zirconium, calcium, and manganese in V2O5.

[0032] 4. The process for preparing high-purity vanadium pentoxide in the present invention returns the chlorine gas in the roasting tail gas to the chloride process titanium dioxide production system after washing, cooling, and drying, recycling the chlorine gas, reducing the production cost of chloride process titanium dioxide, and avoiding environmental pollution caused by chlorine gas emissions. Description of the Drawings

[0033] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0034] Figure 1 It is the process flow diagram of the process for preparing high-purity vanadium pentoxide without ammonium from the waste acid of chloride process titanium dioxide in the present invention;

[0035] Figure 2 It is the process flow diagram of the ammonium salt vanadium precipitation process in the prior art. Detailed Embodiments

[0036] The following will clearly and completely describe the technical solutions of the present invention in combination with the drawings and specific embodiments. However, those skilled in the art will understand that the following described embodiments are some embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention. For those not specified in the embodiments, the conventional conditions or the conditions recommended by the manufacturer are followed. The reagents or instruments not specified by the manufacturer can be obtained as conventional products through commercial purchase.

[0037] A process for preparing high-purity vanadium pentoxide without ammonium from waste acid of titanium dioxide by chlorination method, comprising the following steps: Step S1, pretreatment: adjusting the pH of the waste acid of titanium dioxide by chlorination method to 0.6-1 with alkali liquor, the pH value including but not limited to 0.6, 0.7, 0.8, 0.9, 1, adjusting the temperature to 50-60 °C, including but not limited to 50 °C, 51 °C, 52 °C, 53 °C, 54 °C, 55 °C, 56 °C, 57 °C, 58 °C, 59 °C, 60 °C, then adding 10-20 ppm of flocculant, the dosage of flocculant including but not limited to 10 ppm, 11 ppm, 12 ppm, 13 ppm, 14 ppm, 15 ppm, 16 ppm, 17 ppm, 18 ppm, 19 ppm, 20 ppm, stirring at a speed of 30-50 r / min, the speed including but not limited to 30 r / min, 32 r / min, 34 r / min, 36 r / min, 38 r / min, 40 r / min, 42 r / min, 44 r / min, 46 r / min, 48 r / min, 50 r / min, stirring for 5-10 min, including but not limited to 5 min, 6 min, 7 min, 8 min, 9 min, 10 min, and filtering to remove suspended solids and hydrolysis products of titanium and zirconium impurities;

[0038] Preferably, the flocculant is a cationic flocculant;

[0039] Preferably, the flocculant is one of polyacrylamide (abbreviation: PAM), polyaluminum chloride (abbreviation: PAC), and cationic polyacrylamide (abbreviation: CPAM);

[0040] Step S2, primary extraction of vanadium: using 25% P204 + 5% TBP + 70% sulfonated kerosene (volume ratio) as the extractant, O / A = 1:3-5, including but not limited to 1:3, 1:4, 1:5, and performing countercurrent extraction of the pretreated waste acid of titanium dioxide by chlorination method for 6-10 stages, including but not limited to 6 stages, 7 stages, 8 stages, 9 stages, 10 stages, with the extraction rate of vanadium reaching over 98%;

[0041] Step S3, primary stripping of vanadium: using 3-4 mol / L hydrochloric acid for the loaded organic phase after extracting vanadium, the hydrochloric acid concentration including but not limited to 3 mol / L, 3.2 mol / L, 3.4 mol / L, 3.5 mol / L, 3.6 mol / L, 3.8 mol / L, 4 mol / L, and performing stripping for 6-9 stages to obtain the primary stripped vanadium solution, including but not limited to 6 stages, 7 stages, 8 stages, 9 stages, with the stripping rate of vanadium being greater than 97%;

[0042] Step S4, primary impurity removal: First, acidify 20% N235 + 5% isooctanol + 75% kerosene (by volume). The acidifying water is 3.0 - 4.0N hydrochloric acid, and the hydrochloric acid acidity includes but is not limited to 3.0N, 3.1N, 3.2N, 3.3N, 3.4N, 3.5N, 3.6N, 3.7N, 3.8N, 3.9N, 4.0N. The acidification phase ratio O / A = 1 - 3:1, including but not limited to 1:1, 2:1, 3:1. After acidification, extract and remove iron from the primary vanadium-containing solution. The extraction phase ratio O / A = 1:6 - 8, including but not limited to 1:6, 1:7, 1:8. Perform 1 - 3 stages of extraction, including but not limited to 1 stage, 2 stages, 3 stages. After extraction, the iron content drops to 0.12 mg / L, and the iron removal rate is greater than 99.9%;

[0043] Step S5, secondary impurity removal: After removing iron, add liquid alkali to the feed solution to adjust the acidity to 1.0 - 1.5N, including but not limited to 1.0N, 1.1N, 1.2N, 1.3N, 1.4N, 1.5N. Use 25% P204 + 5% TBP + 70% sulfonated kerosene (by volume), according to the phase ratio O / A = 2 - 4:1, including but not limited to 2:1, 3:1, 4:1. Perform 12 - 15 stages of countercurrent extraction, including but not limited to 12 stages, 13 stages, 14 stages, 15 stages. Continuously operate until the yttrium content in the outlet feed solution is less than 7 ppm, and the yttrium removal rate is greater than 99.9%. Carry out 3 - 5 stages of countercurrent washing on the loaded organic phase and hydrochloric acid with a pH of 1.0 - 2.0 according to the phase ratio O / A = 2 - 4:1. The hydrochloric acid pH value includes but is not limited to 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, and the phase ratio O / A includes but is not limited to 2:1, 3:1, 4:1. The number of countercurrent washing stages includes but is not limited to 3 stages, 4 stages, 5 stages;

[0044] Step S6, secondary extraction of vanadium: Adjust the pH of the feed solution after secondary impurity removal to 0.6 - 1. Use 25% P204 + 5% TBP + 70% sulfonated kerosene (by volume) to extract vanadium according to the phase ratio O / A = 2 - 4:1. The pH value includes but is not limited to 0.6, 0.7, 0.8, 0.9, 1, and the phase ratio O / A includes but is not limited to 2:1, 3:1, 4:1, to further separate impurities such as aluminum, calcium, magnesium, silicon, sodium, and manganese. Carry out 3 - 5 stages of countercurrent washing on the loaded organic phase and hydrochloric acid with a pH of 1.0 - 2.0 according to the phase ratio O / A = 2 - 4:1. The hydrochloric acid pH value includes but is not limited to 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, and the phase ratio O / A includes but is not limited to 2:1, 3:1, 4:1. The number of countercurrent washing stages includes but is not limited to 3 stages, 4 stages, 5 stages;

[0045] Step S7, secondary vanadium stripping: The secondary vanadium-loaded organic phase is stripped with 5-6M hydrochloric acid, including but not limited to 5M, 5.5M, 6M, and multi-stage countercurrent stripping is adopted. According to the phase ratio O / A = 3-5:1, including but not limited to 3:1, 4:1, 5:1, until the concentration of the secondary vanadium stripping solution at the outlet is greater than 160 g / L;

[0046] Step S8, oil removal: The secondary vanadium stripping solution is passed through an oil removal resin for oil removal. After oil removal, almost no vanadium is lost, the oil content at the outlet is less than 0.15 mg / L, and the oil removal rate is greater than 99.5%;

[0047] Preferably, the oil removal resin is a macroporous adsorption resin, and the macroporous adsorption resin is a macroporous amine resin or a macroporous straight-chain alkyl resin; Step S9, drying: The degreased secondary vanadium stripping solution is evaporated and dried at 200-300 °C. The evaporation temperature includes but not limited to 200 °C, 210 °C, 220 °C, 230 °C, 240 °C, 250 °C, 260 °C, 270 °C, 280 °C, 290 °C, 300 °C, and stirred and evaporated at a rotation speed of 20-30 r / min, including but not limited to 20 r / min, 21 r / min, 22 r / min, 23 r / min, 24 r / min, 25 r / min, 26 r / min, 27 r / min, 28 r / min, 29 r / min, 30 r / min, to obtain VOCl2 solid;

[0048] Step S10, roasting: The VOCl2 solid is roasted at 520-600 °C for 2-3 h. The roasting temperature includes but not limited to 520 °C, 530 °C, 540 °C, 550 °C, 560 °C, 570 °C, 580 °C, 590 °C, 600 °C, and the roasting time includes but not limited to 2 h, 2.5 h, 3 h, and decomposed into V2O5 with a purity ≥ 99.9% and a vanadium recovery rate ≥ 99%;

[0049] Step S11, tail gas recovery: The roasting tail gas is chlorine gas, which is returned to the titanium dioxide by chloride process production system after washing, cooling and drying.

[0050] Example 1

[0051] A process for preparing high-purity vanadium pentoxide without ammonium from waste acid of titanium dioxide by chloride process includes the following steps: Step S1, pretreatment: Adjust the pH of the waste acid of titanium dioxide by chloride process to 0.6 with an alkali solution, adjust the temperature to 50 °C, then add 10 ppm of flocculant PAM, stir at a rotation speed of 30 r / min for 5 min, and filter to remove suspended solids and hydrolysis products of titanium and zirconium impurities;

[0052] Step S2, primary vanadium extraction: Using 25% P204 + 5% TBP + 70% sulfonated kerosene (by volume) as the extractant, with O / A = 1:3, countercurrent extraction for 6 stages of the pre-treated titanium dioxide waste acid by the chlorination process, the extraction rate of vanadium reaches over 98%;

[0053] Step S3, primary vanadium stripping: Using 3 mol / L hydrochloric acid for the loaded organic phase after vanadium extraction, and obtaining the primary stripped vanadium solution through 6-stage stripping, the vanadium stripping rate is greater than 97%;

[0054] Step S4, primary impurity removal: First, acidify 20% N235 + 5% isooctanol + 75% kerosene (by volume), with the acidifying water being 3.0N hydrochloric acid and the acidifying phase ratio O / A = 1:1. After acidification, extract and remove iron from the primary stripped vanadium solution, with the extraction phase ratio O / A = 1:6, performing 1-stage extraction. After extraction, the iron content drops to 0.12 mg / L, and the iron removal rate is greater than 99.9%;

[0055] Step S5, secondary impurity removal: After iron removal, add liquid caustic to the feed solution to adjust the acidity to 1.0N. Use 25% P204 + 5% TBP + 70% sulfonated kerosene (by volume), with a phase ratio of O / A = 2:1, and perform 12-stage countercurrent extraction. Continuously operate until the yttrium content in the outlet feed solution is less than 7 ppm, and the yttrium removal rate is greater than 99.9%; Perform 3-stage countercurrent washing on the loaded organic phase and hydrochloric acid with pH 1.0 at a phase ratio of O / A = 2:1;

[0056] Step S6, secondary vanadium extraction: Adjust the pH of the feed solution after secondary impurity removal to 0.6. Use 25% P204 + 5% TBP + 70% sulfonated kerosene (by volume), and extract vanadium at a phase ratio of O / A = 2:1 to further separate impurities such as aluminum, calcium, magnesium, silicon, sodium, and manganese; Perform 3-stage countercurrent washing on the loaded organic phase and hydrochloric acid with pH 1.0 at a phase ratio of O / A = 2:1;

[0057] Step S7, secondary vanadium stripping: Use 5M hydrochloric acid to strip the loaded organic phase after secondary vanadium extraction, adopt multi-stage countercurrent stripping, with a phase ratio of O / A = 3:1, until the concentration of the secondary stripped vanadium solution at the outlet is greater than 160 g / L;

[0058] Step S8, oil removal: Pass the secondary stripped vanadium solution through macroporous amine resin for oil removal. After oil removal, there is almost no loss of vanadium, the petroleum substances at the outlet are less than 0.15 mg / L, and the oil removal rate is greater than 99.5%;

[0059] Step S9, drying: Evaporate and dry the secondary stripped vanadium solution after oil removal at 200 °C, stir and evaporate at a rotation speed of 20 r / min to obtain VOCl2 solid;

[0060] Step S10, roasting: Roast the VOCl2 solid at 520 °C for 2 h to decompose it into V2O5, with a purity of 99.92% and a vanadium recovery rate of 99.20%;

[0061] Step S11, Tail gas recovery: The roasting tail gas is chlorine gas, which is returned to the chlorination process titanium dioxide production system after washing, cooling, and drying.

[0062] Example 2

[0063] A process for preparing high-purity vanadium pentoxide without ammonium from waste acid of chlorination process titanium dioxide includes the following steps: Step S1, Pretreatment: Adjust the pH of the waste acid of chlorination process titanium dioxide to 0.8 with alkali solution, adjust the temperature to 55 °C, then add 15 ppm of flocculant PAC, stir at a speed of 40 r / min for 8 min, and filter to remove suspended solids and hydrolysis products of titanium and zirconium impurities.

[0064] Step S2, First extraction of vanadium: Use 25% P204 + 5% TBP + 70% sulfonated kerosene (volume ratio) as the extractant, O / A = 1:4, and perform countercurrent extraction on the pretreated waste acid of chlorination process titanium dioxide for 8 stages. The extraction rate of vanadium reaches over 98%.

[0065] Step S3, First stripping of vanadium: Use 3.5 mol / L hydrochloric acid for the loaded organic phase after extracting vanadium, and perform 8-stage stripping to obtain the first stripping vanadium solution. The stripping rate of vanadium is greater than 97%.

[0066] Step S4, First impurity removal: First acidify 20% N235 + 5% isooctanol + 75% kerosene (volume ratio) with 3.5 N hydrochloric acid as the acidifying water, with an acidifying phase ratio of O / A = 2:1. After acidification, extract and remove iron from the first stripping vanadium solution, with an extraction phase ratio of O / A = 1:7, and perform 2-stage extraction. After extraction, the iron content drops to 0.12 mg / L, and the iron removal rate is greater than 99.9%.

[0067] Step S5, Second impurity removal: After removing iron, add liquid alkali to the feed liquid to adjust the acidity to 1.2 N. Use 25% P204 + 5% TBP + 70% sulfonated kerosene (volume ratio), with a phase ratio of O / A = 3:1, and perform 14-stage countercurrent extraction. Continuously operate until the yttrium content in the outlet feed liquid is less than 7 ppm, and the yttrium removal rate is greater than 99.9%. Wash the loaded organic phase and hydrochloric acid with pH 1.5 in a countercurrent manner with a phase ratio of O / A = 3:1 for 4 stages.

[0068] Step S6, Second extraction of vanadium: Adjust the pH of the feed liquid after the second impurity removal to 0.8, use 25% P204 + 5% TBP + 70% sulfonated kerosene (volume ratio), and extract vanadium with a phase ratio of O / A = 3:1 to further separate impurities such as aluminum, calcium, magnesium, silicon, sodium, and manganese. Wash the loaded organic phase and hydrochloric acid with pH 1.5 in a countercurrent manner with a phase ratio of O / A = 3:1 for 4 stages.

[0069] Step S7, secondary vanadium stripping: The secondary vanadium-loaded organic phase is stripped with 5.5 M hydrochloric acid, and multi-stage countercurrent stripping is adopted. According to the phase ratio O / A = 4:1, until the concentration of the secondary vanadium stripping solution at the outlet is greater than 160 g / L;

[0070] Step S8, oil removal: The secondary vanadium stripping solution is passed through a macroporous amine resin for oil removal. After oil removal, almost no vanadium is lost, the oil content at the outlet is less than 0.15 mg / L, and the oil removal rate is greater than 99.5%;

[0071] Step S9, drying: The degreased secondary vanadium stripping solution is evaporated and dried at 250 °C, stirred and evaporated at a rotation speed of 25 r / min to obtain VOCl2 solid;

[0072] Step S10, roasting: The VOCl2 solid is roasted at 560 °C for 2.5 h to decompose into V2O5, with a purity of 99.93% and a vanadium yield of 99.30%;

[0073] Step S11, tail gas recovery: The roasting tail gas is chlorine gas, which is returned to the titanium dioxide production system by chlorination method after washing, cooling and drying.

[0074] Example 3

[0075] A process for preparing high-purity vanadium pentoxide without ammonium from the waste acid of titanium dioxide by chlorination method, comprising the following steps: Step S1, pretreatment: Adjust the pH of the waste acid of titanium dioxide by chlorination method to 1 with an alkali solution, adjust the temperature to 60 °C, then add 20 ppm of flocculant CPAM, stir at a rotation speed of 50 r / min for 10 min, and filter to remove the suspended matter and the hydrolysis products of titanium and zirconium impurities;

[0076] Step S2, primary vanadium extraction: Using 25% P204 + 5% TBP + 70% sulfonated kerosene (volume ratio) as the extractant, O / A = 1:5, countercurrent extraction of the pretreated waste acid of titanium dioxide by chlorination method for 10 stages, and the vanadium extraction rate reaches more than 98%;

[0077] Step S3, primary vanadium stripping: The vanadium-loaded organic phase after vanadium extraction is stripped with 4 mol / L hydrochloric acid, and the primary vanadium stripping solution is obtained after 9-stage stripping, and the vanadium stripping rate is greater than 97%;

[0078] Step S4, primary impurity removal: First, acidify 20% N235 + 5% isooctanol + 75% kerosene (volume ratio), the acidifying water is 4.0 N hydrochloric acid, the acidifying phase ratio O / A = 3:1, after acidification, extract and remove iron from the primary vanadium stripping solution, the extraction phase ratio O / A = 1:8, carry out 3-stage extraction, and the iron content drops to 0.12 mg / L after extraction, and the iron removal rate is greater than 99.9%;

[0079] Step S5, Secondary impurity removal: After iron removal, the acidity of the feed liquid is adjusted to 1.5N with liquid caustic soda. Using 25% P204 + 5% TBP + 70% sulfonated kerosene (by volume), at a phase ratio of O / A = 4:1, after 15 - stage counter - current extraction, continuously operate until the yttrium content in the outlet feed liquid is less than 7 ppm and the removal rate of yttrium is greater than 99.9%. Wash the loaded organic phase and hydrochloric acid with pH 2.0 at a phase ratio of O / A = 4:1 for 5 - stage counter - current washing;

[0080] Step S6, Secondary vanadium extraction: Adjust the pH of the feed liquid after secondary impurity removal to 1. Use 25% P204 + 5% TBP + 70% sulfonated kerosene (by volume), extract vanadium at a phase ratio of O / A = 4:1 to further separate impurities such as aluminum, calcium, magnesium, silicon, sodium, and manganese. Wash the loaded organic phase and hydrochloric acid with pH 2.0 at a phase ratio of O / A = 4:1 for 5 - stage counter - current washing;

[0081] Step S7, Secondary stripping of vanadium: Strip the loaded organic phase of secondary vanadium extraction with 6M hydrochloric acid, using multi - stage counter - current stripping, at a phase ratio of O / A = 5:1 until the concentration of the secondary stripped vanadium liquid at the outlet is greater than 160 g / L;

[0082] Step S8, Oil removal: Pass the secondary stripped vanadium liquid through a macroporous straight - chain alkyl resin for oil removal. After oil removal, the loss of vanadium is almost negligible, the oil content at the outlet is less than 0.15 mg / L, and the removal rate of oil is greater than 99.5%;

[0083] Step S9, Drying: Evaporate and dry the secondary stripped vanadium liquid after oil removal at 300 °C, stir and evaporate at a rotation speed of 30 r / min to obtain VOCl2 solid;

[0084] Step S10, Roasting: Roast the VOCl2 solid at 600 °C for 3 h to decompose it into V2O5, with a purity of 99.95% and a vanadium recovery rate of 99.30%;

[0085] Step S11, Tail gas recovery: The roasting tail gas is chlorine, which is returned to the titanium dioxide production system by chlorination method after washing, cooling, and drying treatment.

[0086] Comparative Example 1

[0087] The difference between this comparative example and Example 1 is that: in Step S2, the extractant for primary vanadium extraction is: 25% P507 + 5% TBP + 70% sulfonated kerosene (by volume), and the extraction rate of vanadium is 96%;

[0088] In Step S6, the extractant for secondary vanadium extraction is: 25% P507 + 5% TBP + 70% sulfonated kerosene (by volume);

[0089] In Step S10, after roasting, V2O5 is obtained, and the vanadium recovery rate is 95%.

[0090] Comparative Example 2

[0091] The difference between this comparative example and Example 1 lies in: in step S4, the extractant for primary impurity removal is: 20% P204 + 5% TBP + 70% sulfonated kerosene (volume ratio), and the iron removal rate is 95%; in step S5, the extractant for secondary impurity removal is: 25% P507 + 5% TBP + 70% sulfonated kerosene (volume ratio), and the yttrium removal rate is 83.35%;

[0092] The purity of V2O5 obtained by roasting in step S10 is 99.05%.

[0093] Comparative Example 3

[0094] A process for preparing high-purity vanadium pentoxide without ammonium from titanium white waste acid by the chlorination method includes the following steps: Step S1, pretreatment: adjusting the pH of the titanium white waste acid by the chlorination method to 0.6 with an alkali solution, adjusting the temperature to 50°C, then adding 10 ppm of flocculant PAM, stirring at a speed of 30 r / min for 5 min, and filtering to remove suspended solids and hydrolysis products of titanium and zirconium impurities;

[0095] Step S2, primary extraction of vanadium: using 25% P204 + 5% TBP + 70% sulfonated kerosene (volume ratio) as the extractant, O / A = 1:3, and performing countercurrent 6-stage extraction on the pretreated titanium white waste acid by the chlorination method;

[0096] Step S3, primary stripping of vanadium: using 3 mol / L hydrochloric acid for the loaded organic phase after extracting vanadium, and obtaining the primary stripped vanadium solution through 6-stage stripping;

[0097] Step S4, primary impurity removal: first acidifying 20% N235 + 5% isooctanol + 75% kerosene (volume ratio), the acidifying water is 3.0 N hydrochloric acid, the acidifying phase ratio O / A = 1:1, and after acidification, extracting and removing iron from the primary stripped vanadium solution, the extraction phase ratio O / A = 1:6, and performing 1-stage extraction;

[0098] Step S5, oil removal: passing the primary stripped vanadium solution after primary impurity removal through a macroporous amine resin for oil removal;

[0099] Step S6, drying: evaporating and drying the primary stripped vanadium solution at 200°C, stirring and evaporating at a speed of 20 r / min to obtain VOCl2 solid;

[0100] Step S7, roasting: roasting the VOCl2 solid at 520°C for 2 h to decompose it into V2O5, with a purity of 98.32% and a vanadium recovery rate of 99.10%.

[0101] Test example:

[0102] I. The statistical table of the purity and vanadium recovery rate of V2O5 prepared in Examples 1-3 and Comparative Examples 1-3 is shown in Table 1

[0103] Table 1 Statistical Table of the Purity of V2O5 and the Vanadium Recovery Rate Obtained in Examples 1-3 and Comparative Examples 1-3

[0104] Project Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 <![CDATA[Purity of V2O5 (%)]]> 99.92 99.93 99.95 \ 99.05 98.32 Vanadium recovery rate (%) 99.20 99.30 99.30 95 \ 99.10

[0105] As can be seen from the data in Table 1, the extractants for the first-stage vanadium extraction and the second-stage vanadium extraction in Comparative Example 1 are different from those in Example 1. The extraction rate of vanadium in the first-stage vanadium extraction of the present invention reaches more than 98%, and the vanadium recovery rate of V2O5 in the present invention is ≥99.2%. The extraction rate of vanadium in the first-stage vanadium extraction in Comparative Example 1 is 96%, and the vanadium recovery rate of V2O5 is 95%. It can be seen that the extractants for the first-stage vanadium extraction and the second-stage vanadium extraction of the present invention can significantly improve the extraction rate of vanadium by the extractant, and thus greatly improve the vanadium recovery rate in V2O5.

[0106] The extractants for the first-stage impurity removal and the second-stage impurity removal in Comparative Example 2 are different from those in Example 1. The iron removal rate in the first-stage impurity removal of the present invention is greater than 99.9%, and the yttrium removal rate in the second-stage impurity removal is greater than 99.9%. The purity of V2O5 in the present invention is ≥99.92%. The iron removal rate in the first-stage impurity removal in Comparative Example 2 is 95%, and the yttrium removal rate in the second-stage impurity removal is 83.35%. The purity of V2O5 in Comparative Example 2 is 99.05%. It can be seen that the extractants for the first-stage impurity removal and the second-stage impurity removal of the present invention can effectively improve the removal rates of iron and yttrium impurity elements, and thus significantly improve the purity of V2O5.

[0107] In Comparative Example 3, the second-stage impurity removal, the second-stage vanadium extraction, and the second-stage vanadium stripping are omitted. The purity of VO in Comparative Example 3 is 98.32%, and the vanadium recovery rate is 99.10%. It can be seen that both the purity and the vanadium recovery rate of VO in Comparative Example 3 have decreased significantly. The present invention adopts a multi-stage extraction and impurity removal process, and the prepared VO has a purity ≥99.92% and a vanadium recovery rate ≥99.2%, which can significantly improve the purity of vanadium pentoxide and the vanadium recovery rate.

[0108] II. The impurity metal contents in the V2O5 prepared in Examples 1-3 and Comparative Examples 2-3 are shown in Table 2

[0109] Table 2 Detection Table of the Impurity Element Contents in the V2O5 Prepared in Examples 1-3 and Comparative Examples 2-3

[0110]

[0111]

[0112] As can be seen from Table 2, by comparing the impurity element contents in the V2O5 prepared in Examples 1-3 with those in Comparative Example 2 and Comparative Example 3, it can be known that: the extractants for the first-stage impurity removal and the second-stage impurity removal and the multi-stage extraction and impurity removal process of the present invention can effectively improve the removal rate of impurity elements in titanium white waste acid by chlorination method, and significantly reduce the contents of impurity elements such as iron, aluminum, titanium, sodium, magnesium, silicon, yttrium, zirconium, and calcium in VO.

Claims

1. A process for preparing high-purity vanadium pentoxide based on ammonium-free titanium dioxide waste acid from the chloride process, characterized in that: The following steps are involved: Step S1, pretreatment: using alkali solution to adjust the pH value of the waste acid of titanium dioxide produced by the chloride process, and then adding a flocculant to filter and remove suspended matter and hydrolysis products of titanium and zirconium impurities; Step S2, primary extraction of vanadium: countercurrent extraction of vanadium in pre-treated chlorination titanium dioxide waste acid; Step S3, primary stripping of vanadium: stripping the loaded organic phase after vanadium extraction with hydrochloric acid to obtain a primary stripping solution; Step S4, primary impurity removal: extracting and removing iron from the primary devanadium solution; Step S5, secondary impurity removal: after iron removal, liquid alkali is added to the feed solution to adjust the acidity, and yttrium is extracted in countercurrent; Step S6, secondary extraction of vanadium: extracting vanadium from the secondary impurity-removed liquid; Step S7, secondary stripping of vanadium: countercurrent stripping of the organic phase loaded with secondary vanadium using hydrochloric acid; Step S8, degreasing: degreasing the secondary vanadium removal liquid through degreasing resin; Step S9, drying: heating and evaporating the de-oiled secondary vanadium solution to dryness to obtain VOCl2 solid; Step S10, calcination: calcine the VOCl2 solid to decompose into V2O5.

2. The process for preparing high-purity vanadium pentoxide from waste acid of titanium dioxide by chloride process without ammonium according to claim 1, characterized in that: In step S1, the pH value of the waste acid of titanium dioxide produced by the chloride process is adjusted to 0.6-1, the temperature is adjusted to 50-60° C., and after adding the flocculant, the mixture is stirred at a speed of 30-50 r / min for 5-10 minutes.

3. The process for preparing high-purity vanadium pentoxide based on ammonium-free waste acid of titanium dioxide by chloride process according to claim 1 or 2, characterized in that: The flocculant is one of polyacrylamide, polyaluminium chloride and cationic polyacrylamide, and the dosage of the flocculant is 10-20 ppm.

4. The process for preparing high-purity vanadium pentoxide based on ammonium-free waste acid of titanium dioxide by chloride process according to claim 1, characterized in that: In step S2, 25% P204+5% TBP+70% sulfonated kerosene is used as the extractant, O / A=1:3-5, and vanadium is extracted in 6-10 stages of countercurrent.

5. The process for preparing high-purity vanadium pentoxide based on ammonium-free waste acid of titanium dioxide by chloride process according to claim 1, characterized in that: In step S3, 3-4 mol / L hydrochloric acid is used to extract the loaded organic phase after vanadium extraction, and the phase is stripped in 6-9 stages to obtain a primary de-vanadium solution.

6. The process for preparing high-purity vanadium pentoxide based on ammonium-free waste acid of titanium dioxide by chloride process according to claim 1, characterized in that: In step S4, 20% N235+5% isooctyl alcohol+75% kerosene is firstly acidified, the acidified water is 3.0-4.0N hydrochloric acid, the acidified phase ratio O / A=1-3:1, and after acidification, the primary devanadium solution is extracted to remove iron, the extraction phase ratio O / A=1:6-8, and 1-3 levels of extraction are performed.

7. The process for preparing high-purity vanadium pentoxide based on ammonium-free waste acid of titanium dioxide by chloride process according to claim 1, characterized in that: In step S5, after iron removal, liquid alkali is added to the feed liquid to adjust the acidity to 1.0-1.5N, 25% P204+5% TBP+70% sulfonated kerosene is used, and yttrium is extracted through 12-15 stages of countercurrent extraction according to the relative ratio O / A=2-4:1, and the yttrium content of the outlet feed liquid is continuously operated until the yttrium content of the feed liquid is less than 7ppm; the loaded organic phase and hydrochloric acid with a pH of 1.0-2.0 are subjected to 3-5 stages of countercurrent washing according to the relative ratio O / A=2-4:

1.

8. The process for preparing high-purity vanadium pentoxide based on ammonium-free waste acid of titanium dioxide by chloride process according to claim 1, characterized in that: In step S6, the pH value of the feed liquid after the secondary impurity removal is adjusted to 0.6-1, and 25% P204+5% TBP+70% sulfonated kerosene is used to extract vanadium at a ratio of O / A=2-4:1, and the impurities of aluminum, calcium, magnesium, silicon, sodium and manganese are separated; the loaded organic phase and hydrochloric acid with a pH of 1.0-2.0 are subjected to 3-5 levels of countercurrent washing at a ratio of O / A=2-4:

1.

9. The process for preparing high-purity vanadium pentoxide based on ammonium-free waste acid of titanium dioxide by chloride process according to claim 1, characterized in that: In step S7, the loaded organic phase is stripped using 5-6M hydrochloric acid, with a phase ratio of O / A=3-5:1, and multi-stage countercurrent stripping is performed until the concentration of the secondary de-vanadium solution at the outlet is greater than 160 g / L.

10. The process for preparing high-purity vanadium pentoxide based on ammonium-free waste acid of titanium dioxide by chloride process according to claim 1, characterized in that: The process also includes step S11, tail gas recovery: the roasting tail gas is chlorine, which is returned to the chloride process titanium dioxide production system after washing, cooling and drying.

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