Method for separating vanadium and titanium from acidic vanadium and titanium mixed solution and producing titanium dioxide and vanadium dioxide

Abstract

The invention provides a method for separating vanadium and titanium from an acidic vanadium-titanium mixed solution and producing titanium dioxide and vanadium dioxide, which comprises the following steps of: separating titanium in the solution in the form of titanium phosphate precipitate by taking phosphoric acid and / or phosphate as a titanium precipitation agent under an acidic reduction system, and transforming the titanium phosphate precipitate by using sodium hydroxide to obtain a titanium dioxide product and a sodium phosphate solution, recycling the sodium phosphate solution; the method comprises the following steps: extracting vanadium from a titanium precipitation mother solution by using an acidic phosphorus type extractant, carrying out reverse extraction on a vanadium-loaded organic phase by using hydrochloric acid to obtain a reverse extraction solution, hydrolyzing vanadium oxide cations (VO2 < + >) in the reverse extraction solution by adjusting the pH of the reverse extraction solution to generate precipitates, and calcining the precipitates to obtain the product vanadium dioxide. The method provided by the invention is suitable for treatment of a complex acidic vanadium-titanium mixed solution, the phosphoric acid titanium precipitation method has high selectivity on titanium, and efficient separation of vanadium and titanium is realized with relatively low vanadium loss; and secondly, the transformation of titanium phosphate enables the titanium precipitation agent to be recycled, so that the production cost is reduced, and meanwhile, a high-value titanium dioxide product is prepared.

Description

Technical Field

[0001] The present invention relates to the technical field of non-ferrous metal metallurgy, and particularly relates to a method for separating vanadium and titanium from an acidic vanadium-titanium mixed solution and producing titanium dioxide and vanadium dioxide. Background Art

[0002] At present, for acidic feed liquids containing both vanadium and titanium in industry, a process route is often adopted in which an extractant is used to preferentially extract titanium under high acid, and the vanadium is extracted from the mother liquor after titanium extraction through neutralization and filtration. For vanadium-containing feed liquids with a low titanium content, whether an acidic extractant or a basic extractant is used to extract titanium, problems such as long phase separation time and difficult phase separation due to emulsification of the organic phase are likely to occur; for vanadium-containing feed liquids with a high titanium content, the organic phase after titanium extraction will carry a high concentration of titanium, and it is difficult to find an anti-extraction agent with good anti-extraction effect. Therefore, the traditional process for anti-extracting titanium requires the use of high-concentration sulfuric acid and hydrogen peroxide for countercurrent anti-extraction through more than ten stages, and the process operation flow is long and the workload is large. At the same time, based on the difference in the pH values of hydrolysis precipitation of vanadium and titanium, by adjusting the pH of the solution to preferentially hydrolyze and precipitate titanium to separate vanadium and titanium, a large amount of vanadium ions and other impurity metal ions will be entrained while 2+ colloidal titanium oxyhydroxide precipitate is formed, which not only cannot prepare titanium products but also causes a large loss of high-value vanadium. In addition, the traditional process for extracting vanadium will produce ammonia-nitrogen wastewater during the process of ammonium salt precipitation of vanadium from the anti-extraction solution, and the treatment of ammonia-nitrogen wastewater increases the input of the entire process cost. Summary of the Invention

[0003] The purpose of the present invention is to provide a method for separating vanadium and titanium from an acidic vanadium-titanium mixed solution and producing titanium dioxide and vanadium dioxide, aiming to solve the problems of difficult anti-extraction of titanium, long process flow, large operation workload, and large generation of ammonia-nitrogen wastewater in the existing process for separating titanium and vanadium.

[0004] To achieve the above purpose, the present invention provides a method for separating vanadium and titanium from an acidic vanadium-titanium mixed solution and producing titanium dioxide and vanadium dioxide, including the following steps:

[0005] (1) Phosphoric acid and / or phosphate are added to the acidic vanadium-titanium mixed solution to precipitate titanium, and titanium phosphate precipitate and a mother liquor containing vanadium after titanium precipitation are obtained through filtration and washing. The acidic vanadium-titanium mixed solution is a reducing solution, and the H + concentration of the solution is 1-2.5 mol / L, the vanadium in the solution shows a +4 valence (VO 2+ ), and the impurity iron shows a +2 valence.

[0006] (2) The titanium phosphate precipitate is transformed with a sodium hydroxide solution to obtain a sodium phosphate solution and a titanium hydroxide precipitate. The sodium phosphate solution can be returned to step (1) for recycling as a titanium precipitation agent, and the titanium hydroxide precipitate is washed and calcined to obtain the product titanium dioxide.

[0007] (3) Extract vanadium from the titanium precipitation mother liquor in step (1) with an acidic phosphorus extractant to obtain an organic phase loaded with vanadium.

[0008] (4) Back-extract the organic phase loaded with vanadium with hydrochloric acid to obtain a vanadium-containing back-extract solution.

[0009] (5) Add an alkaline vanadium-precipitating agent to the vanadium-containing back-extract solution to promote the hydrolysis and precipitation of vanadyl cations (VO 2+ ), and obtain vanadyl hydroxide precipitate after washing and filtration.

[0010] (6) Calcinate the vanadyl hydroxide precipitate under closed conditions to obtain the product vanadium pentoxide.

[0011] Preferably, the phosphate in step (1) includes one or more of sodium phosphate, disodium hydrogen phosphate, and sodium dihydrogen phosphate, the precipitation pH is less than 1, the reaction temperature is 70-90 °C, and the reaction time is 0.5-3 h.

[0012] Preferably, the concentration of the sodium hydroxide solution in step (2) is 1.5-6 mol / L, the reaction temperature is 25-95 °C, the reaction time is 2-4 h, and the solid-liquid ratio S / L = 1:1-1:20.

[0013] Preferably, the calcination temperature in step (2) is 400-500 °C, and the calcination time is 4-6 h.

[0014] Preferably, the acidic phosphorus extractant in step (3) includes one or more of P204, P507, and Cyanex272, and the total concentration is 10-30%; the modifier added during extraction is one of TBP, isooctanol, or sec-octanol, and the total concentration is 5-20%; the extraction conditions are: countercurrent extraction, extraction phase ratio O / A = 1:1-1:5, extraction stage number 2-8, and temperature 20-50 °C.

[0015] Preferably, the acidity of the hydrochloric acid in step (4) is 1-6 mol / L. The back-extraction conditions are: countercurrent back-extraction, back-extraction phase ratio O / A = 3:1-6:1, back-extraction stage number 2-6, and temperature 20-50 °C.

[0016] Preferably, the alkaline vanadium-precipitating agent in step (5) includes one or more of sodium hydroxide, sodium carbonate, sodium bicarbonate, calcium oxide, calcium carbonate, and calcium hydroxide. The pH value of hydrolysis precipitation is 3.7-4.8, the reaction temperature is 5-85 °C, and the hydrolysis reaction time is 0.5-5 h.

[0017] Preferably, the calcination temperature in step (6) is 500-600 °C, and the calcination time is 4-8 h.

[0018] Compared with the prior art, the technical solution adopted by the present invention has the following advantages:

[0019] (1) In the present invention, phosphoric acid and / or phosphate are used as titanium precipitation agents to precipitate titanium in the acidic feed liquid as titanium phosphate, achieving efficient separation of titanium and vanadium in one step, shortening the process flow, and at the same time solving the problems of long phase separation time and difficult stripping in the traditional extraction separation process. In addition, after the titanium phosphate precipitate is transformed by sodium hydroxide, a sodium phosphate solution and a titanium hydroxide precipitate are obtained. The sodium phosphate solution can be recycled as a titanium precipitation agent, reducing reagent consumption and wastewater discharge, with the characteristics of being clean and efficient, and having guiding significance for industrial practice.

[0020] (2) In the present invention, alkaline precipitation agents such as sodium hydroxide, sodium carbonate, sodium bicarbonate, and calcium oxide are selected to adjust the pH for hydrolysis precipitation of vanadium, avoiding the generation of ammonia-nitrogen wastewater from the source, which is green and clean.

[0021] (3) The present invention is not affected by the titanium content in the acidic vanadium-titanium mixed solution, and can achieve good separation effect of vanadium and titanium for solutions with low or high titanium content. Specific Embodiments

[0022] The following specific examples are used to further illustrate the technical solutions of the present invention. Those skilled in the art should know that the examples are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0023] In the examples, unless otherwise specified, the technical means used are conventional technical means in the art.

[0024] Example 1

[0025] (1) Preparation of the raw material liquid: Take one of the titanium white waste acid, acid leaching solution of vanadium-titanium magnetite, and acid leaching solution of vanadium-containing waste catalyst. The H + concentration is 1 - 2.5 mol / L. Add reducing agents such as reduced iron powder and sodium sulfite to make V show +4 valence and Fe show +2 valence, and filter for later use.

[0026] (2) Slowly add 0.7 mol / L sodium phosphate solution to the above raw material liquid while stirring. The addition amount of sodium phosphate is n(Na 3 PO 4 ) / n(Ti) = 1.4. Stir and precipitate at 80 °C for 1 h. The precipitation rate of titanium reaches 96.86%, and the entrainment loss rate of vanadium is 4.26%.

[0027] (3) Add 2 mol / L sodium hydroxide solution to the titanium phosphate precipitate obtained after washing and filtering. Under the conditions of reaction temperature of 90 °C, reaction time of 2 h, and solid-liquid ratio of 1:15, the leaching rate of phosphorus reaches 99.65%. The obtained sodium phosphate leaching solution can be returned to (2) as a titanium precipitation agent.

[0028] The leaching residue is washed with deionized water, filtered, and then dried in an oven at 105°C. The dried residue is calcined in a muffle furnace at 500°C for 4 hours to obtain a titanium dioxide product with a purity of 98.7%.

[0029] (4) Take the titanium precipitation mother liquor obtained in step (2), use 20% P204 + 5% sec-octanol + 75% sulfonated kerosene as the extractant, and perform 5-stage countercurrent extraction under the condition of O / A = 1 / 1 to obtain the organic phase loaded with vanadium and the raffinate. The vanadium concentration in the raffinate is lower than 6 mg / L, and the vanadium extraction rate reaches over 99%.

[0030] (5) Select 2 mol / L hydrochloric acid as the stripping agent for the organic phase loaded with vanadium, and perform 4-stage countercurrent stripping under the condition of O / A = 5 / 1. The vanadium stripping rate reaches over 99%, and the vanadium concentration in the stripping solution is 35.4 g / L.

[0031] (6) Slowly add 10 mol / L sodium hydroxide solution to the stripping solution to adjust the pH to 3.8, and stir and hydrolyze for precipitation at 60°C for 2 hours. The precipitation rate of vanadium reaches 99.53%.

[0032] (7) The precipitate obtained by filtration is washed with deionized water and then calcined in a muffle furnace under vacuum for 4 hours at 600°C to obtain a vanadium dioxide product with a purity of 99.2%.

[0033] Example 2

[0034] The difference between this example and Example 1 is that in this example, 0.68 mol / L phosphoric acid solution is slowly added to the raw material liquid while stirring, and the addition amount of phosphoric acid is n(H 3 PO 4 ) / n(Ti) = 1.3. Stir and precipitate at 85°C for 1 hour. The precipitation rate of titanium reaches 96.26%, and the entrainment loss rate of vanadium is 2.93%.

[0035] Example 3

[0036] The difference between this example and Example 1 is that in this example, 0.75 mol / L sodium hydrogen phosphate solution is slowly added to the raw material liquid while stirring, and the addition amount of sodium hydrogen phosphate is n(Na 2 HPO 4 ) / n(Ti) = 1.4. Stir and precipitate at 80°C for 1 hour. The precipitation rate of titanium reaches 97.33%, and the entrainment loss rate of vanadium is 3.48%.

[0037] Example 4

[0038] The difference between this example and Example 1 is that in this example, 0.8 mol / L sodium dihydrogen phosphate solution is slowly added to the raw material liquid while stirring, and the addition amount of sodium dihydrogen phosphate is n(NaH2 PO 4 ) / n(Ti) = 1.4. Stir and precipitate for 1 h at 80 °C, and the precipitation rate of titanium reaches 97.27%, and the entrainment loss rate of vanadium is 3.96%.

[0039] Example 5

[0040] The difference between this example and Example 1 is that in this example, the raw material solution and 0.7 mol / L sodium phosphate solution are slowly added to the base solution while stirring. The base solution is a dilute sulfuric acid solution with pH = 0.5, and the addition amount of sodium phosphate is n(Na 3 PO 4 ) / n(Ti) = 1.4. Stir and precipitate for 1 h at 80 °C, and the precipitation rate of titanium reaches 97.86%, and the entrainment loss rate of vanadium is 2.42%.

[0041] Example 6

[0042] The difference between this example and Example 1 is that in this example, lime slurry with a mass ratio of 1:5 (CaO:H 2 O) is slowly added to the stripping solution to adjust the pH to 4.1, and hydrolysis precipitation is carried out by stirring for 2 h at 80 °C, and the precipitation rate of vanadium reaches 99.33%. The precipitate obtained by filtration is washed with deionized water and then placed in a muffle furnace for vacuum calcination for 4 h, and the calcination temperature is 600 °C to obtain a vanadium dioxide product with a purity of 99.01%.

[0043] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can still be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for separating vanadium and titanium from an acidic vanadium-titanium mixed solution to produce titanium dioxide and vanadium dioxide, characterized in that: The following steps are involved: (1) adding phosphoric acid and / or phosphate to an acidic vanadium-titanium mixed solution to precipitate titanium, filtering and washing to obtain a titanium phosphate precipitate and a vanadium-containing titanium precipitation mother solution, wherein the acidic vanadium-titanium mixed solution is a reducing solution, and the solution H + The concentration is 1-2.5 mol / L, the vanadium in the solution is +4 valence, and the impurity iron is +2 valence; (2) The titanium phosphate precipitate is transformed with a sodium hydroxide solution to obtain a sodium phosphate solution and a titanium hydroxide precipitate, wherein the sodium phosphate solution is returned to step (1) and recycled as a titanium precipitating agent, and the titanium hydroxide precipitate is washed and calcined to obtain a product titanium dioxide; (3) extracting vanadium from the titanium precipitation mother liquor in step (1) with an acidic phosphorus-based extractant to obtain an organic phase loaded with vanadium; (4) stripping the vanadium-loaded organic phase with hydrochloric acid to obtain a vanadium-containing stripping solution; (5) adding an alkaline vanadium precipitating agent to the vanadium-containing stripping solution to promote the hydrolysis and precipitation of vanadium oxycations, and obtaining a vanadium hydroxide precipitate by washing and filtering; (6) The vanadium hydroxide precipitate is calcined under closed conditions to obtain the product vanadium dioxide.

2. The method according to claim 1, characterized in that The phosphate in step (1) includes one or more of sodium phosphate, sodium monohydrogen phosphate, and sodium dihydrogen phosphate, the precipitation pH is less than 1, the reaction temperature is 70-90° C., and the reaction time is 0.5-3 h.

3. The method according to claim 1, characterized in that The concentration of the sodium hydroxide solution in step (2) is 1.5-6 mol / L, the reaction temperature is 25-95° C., the reaction time is 2-4 h, and the solid-liquid ratio is S / L=1:1-1:

20.

4. The method according to claim 1, characterized in that: The calcination temperature in step (2) is 400-500° C., and the calcination time is 4-6 hours.

5. The method according to claim 1, characterized in that The acidic phosphorus extractant in step (3) includes one or more of P204, P507, and Cyanex272, with a total concentration of 10 to 30%; the modifier added during extraction is one of TBP, isooctyl alcohol or sec-octanol, with a total concentration of 5 to 20%; the extraction conditions are: countercurrent extraction, extraction phase ratio O / A=1:1 to 1:5, extraction level 2 to 8, and temperature 20 to 50°C.

6. The method according to claim 1, characterized in that The acidity of the hydrochloric acid in step (4) is 1 to 6 mol / L; the stripping conditions are: countercurrent stripping, stripping ratio O / A=3:1 to 6:1, stripping stage 2 to 6, and temperature 20 to 50°C.

7. The method according to claim 1, characterized in that: The alkaline vanadium precipitating agent in step (5) comprises one or more of sodium hydroxide, sodium carbonate, sodium bicarbonate, calcium oxide, calcium carbonate and calcium hydroxide; the hydrolysis precipitation pH value is 3.7-4.8, the reaction temperature is 5-85° C., and the hydrolysis reaction time is 0.5-5 h.

8. The method according to claim 1, characterized in that: In step (6), the calcination temperature is 500-600° C. and the calcination time is 4-8 hours.