A method for recovering tungsten from tungsten waste catalyst crystals

Abstract

The present invention provides a method for recovering tungsten from tungsten waste catalyst crystals, and belongs to the field of solid waste resource utilization. The present invention mixes the tungsten waste catalyst crystals with water and then performs leaching. During the leaching process, tungsten is basically completely dissolved without tungsten loss, thereby improving the recovery rate of tungsten; and after the leaching solution undergoes thiolation reaction and precipitation, a new type of extractant is used to synergistically improve the separation efficiency of tungsten and molybdenum.

Description

Technical Field

[0001] The invention relates to the field of solid waste resource utilization, and in particular to a method for recovering tungsten from tungsten waste catalyst crystals. Background Art

[0002] SCR catalysts are mainly used in thermal power plants for flue gas denitration, reducing nitrogen oxides in flue gas to water and nitrogen. The main body of the SCR catalyst is usually titanium dioxide, with rod-shaped silicon dioxide and rod-shaped aluminum oxide embedded in the main body. In addition, in order to improve the mechanical properties of the SCR catalyst during the manufacturing process, tungsten trioxide is often used as a catalyst additive and distributed on the surface of the main body.

[0003] After long-term use, SCR catalysts lose their activity due to physical blockage, chemical poisoning, and wear and tear, and become waste SCR catalysts. The traditional process for treating waste SCR catalysts is to crush the waste SCR catalysts, separate the tungsten from the vanadium and titanium in the catalyst by high-temperature sodium roasting, obtain tungsten waste catalyst crystals, and then use extraction to separate tungsten from molybdenum, so as to effectively recover tungsten and molybdenum in the tungsten waste catalyst crystals. However, the recovery rate of tungsten and the efficiency of tungsten-molybdenum separation in traditional processes still need to be improved. Summary of the invention

[0004] The present invention provides a method for recovering tungsten in tungsten waste catalyst crystals. The recovery method of the present invention improves the recovery rate of tungsten in tungsten waste catalyst crystals and the tungsten-molybdenum separation efficiency.

[0005] The present invention provides a method for recovering tungsten from tungsten waste catalyst crystals, comprising the following steps:

[0006] The tungsten waste catalyst crystals are mixed with water and then leached to obtain a leaching solution containing sodium tungstate and sodium molybdate;

[0007] The leachate is mixed with an acid and an alkali metal sulfide to undergo a sulfidation reaction to obtain Na 2 MoO 4 a precipitate and an aqueous solution containing sodium tungstate and a first residual sodium molybdate;

[0008] The aqueous solution is mixed with a copper salt solution to perform a precipitation reaction to obtain a copper molybdate precipitate and a reaction solution containing sodium tungstate and a second residual sodium molybdate;

[0009] The reaction solution is mixed with an extractant to extract sodium tungstate to obtain an extract; the extractant comprises the following components by volume fraction: 5-7% methyl trioctyl ammonium chloride, 8-10% N1923, 5% sec-octanol and the remainder kerosene;

[0010] The extract is mixed with aqueous ammonia for stripping, a double decomposition reaction occurs, and then the stripping solution obtained is crystallized to obtain ammonium paratungstate.

[0011] Preferably, the tungsten waste catalyst crystals include Na 2 O 60~70%, WO 3 10~14%, SO 3 15~20%, SiO 2 0.5~3%, MoO 3 0.2~0.8%,Al 2 O 3 0.5~2%, CaO 0.5~1.5% and the rest are impurities.

[0012] Preferably, the leaching temperature is 65-75°C and the time is 1-3h;

[0013] The leaching is carried out under stirring conditions; the stirring speed is 280-500 r / min.

[0014] Preferably, the acid comprises dilute sulfuric acid; the concentration of the dilute sulfuric acid is 1.5-3 mol / L.

[0015] Preferably, mixing the leachate with an acid and an alkali metal sulfide comprises: mixing the leachate with an acid, and then mixing the resulting solution with an alkali metal sulfide; the pH value of the solution is 6.5-7.5.

[0016] Preferably, the alkali metal sulfide comprises sodium sulfide.

[0017] Preferably, the liquid-to-solid ratio of the leachate to the alkali metal sulfide is 1000 mL: 1-4 g.

[0018] Preferably, the copper salt solution includes a copper sulfate solution; the concentration of the copper sulfate solution is 3-5 mol / L.

[0019] Preferably, the volume ratio of the aqueous solution to the copper salt solution is 5-7:1.

[0020] Preferably, the volume ratio of the reaction solution to the extractant is 3-4.5:1;

[0021] The extraction temperature is 25-30°C and the extraction time is 10-15 minutes.

[0022] The present invention provides a method for recovering tungsten from tungsten waste catalyst crystals, comprising the following steps:

[0023] The tungsten waste catalyst crystals are mixed with water and then leached to obtain a leaching solution containing sodium tungstate and sodium molybdate;

[0024] The leachate is mixed with an acid and an alkali metal sulfide to undergo a sulfidation reaction to obtain Na 2MoO 4 a precipitate and an aqueous solution containing sodium tungstate and a first residual sodium molybdate;

[0025] The aqueous solution is mixed with a copper salt solution to perform a precipitation reaction to obtain a copper molybdate precipitate and a reaction solution containing sodium tungstate and a second residual sodium molybdate;

[0026] The reaction solution is mixed with an extractant to extract sodium tungstate to obtain an extract; the extractant comprises the following components by volume fraction: 5-7% methyl trioctyl ammonium chloride, 8-10% N1923, 5% sec-octanol and the remainder kerosene;

[0027] The extract is mixed with aqueous ammonia for stripping, a double decomposition reaction occurs, and then the stripping solution obtained is crystallized to obtain ammonium paratungstate.

[0028] The present invention mixes tungsten waste catalyst crystals with water and then performs leaching. In the leaching process, tungsten is basically completely dissolved without tungsten loss, thereby improving the tungsten recovery rate; and after the leaching solution undergoes thiolation reaction and precipitation, a new type of extractant is used to synergistically improve the tungsten-molybdenum separation efficiency. DETAILED DESCRIPTION

[0029] The present invention provides a method for recovering tungsten from tungsten waste catalyst crystals, comprising the following steps:

[0030] The tungsten waste catalyst crystals are mixed with water and then leached to obtain a leaching solution containing sodium tungstate and sodium molybdate;

[0031] The leachate is mixed with an acid and an alkali metal sulfide to undergo a sulfidation reaction to obtain Na 2 MoO 4 a precipitate and an aqueous solution containing sodium tungstate and a first residual sodium molybdate;

[0032] The aqueous solution is mixed with a copper salt solution to perform a precipitation reaction to obtain a copper molybdate precipitate and a reaction solution containing sodium tungstate and a second residual sodium molybdate;

[0033] The reaction solution is mixed with an extractant to extract sodium tungstate to obtain an extract; the extractant comprises the following components by volume fraction: 5-7% methyl trioctyl ammonium chloride, 8-10% N1923, 5% sec-octanol and the remainder kerosene;

[0034] The extract is mixed with aqueous ammonia for stripping, a double decomposition reaction occurs, and then the stripping solution obtained is crystallized to obtain ammonium paratungstate.

[0035] The invention mixes the tungsten waste catalyst crystals with water and then performs leaching to obtain a leaching solution containing sodium tungstate and sodium molybdate.

[0036] In the present invention, the mass ratio of the tungsten waste catalyst crystals to water is preferably 1:3.

[0037] In the present invention, the tungsten waste catalyst crystals preferably include Na 2 O 60~70%, WO 3 10~14%, SO 3 15~20%, SiO 2 0.5~3%, Mo 3 0.2~0.8%,Al 2 O 3 0.5~2%, CaO 0.5~1.5% and the rest are impurities.

[0038] In the present invention, the particle size of the waste tungsten catalyst crystals is preferably 5-15 μm. In a specific embodiment of the present invention, the particle size of the waste tungsten catalyst crystals may be 5 μm, 8 μm, 10 μm, 12 μm or 15 μm.

[0039] In the present invention, the leaching is preferably carried out under stirring; the stirring speed is preferably 280-500 r / min, and in a specific embodiment of the present invention, the stirring speed may be 280 r / min, 320 r / min, 360 r / min, 400 r / min, 450 r / min or 500 r / min; the leaching temperature is preferably 65-75°C, and in a specific embodiment of the present invention, the leaching temperature may be 65°C, 68°C, 70°C, 72°C or 75°C; the time is preferably 1-4 h, and in a specific embodiment of the present invention, the leaching time may be 1 h, 2 h, 3 h or 4 h.

[0040] After obtaining the leaching solution containing sodium tungstate and sodium molybdate, the present invention mixes the leaching solution with an acid and an alkali metal sulfide to carry out a sulfidation reaction to obtain Na 2 MoO 4 The precipitate and the aqueous solution containing sodium tungstate and the first residual sodium molybdate.

[0041] In the present invention, mixing the leachate with an acid and an alkali metal sulfide preferably comprises: mixing the leachate with an acid, and then mixing the resulting solution with an alkali metal sulfide; the pH value of the solution is preferably 6.5-7.5.

[0042] In the present invention, the acid preferably includes dilute sulfuric acid; the concentration of the dilute sulfuric acid is preferably 1.5-3 mol / L. In a specific embodiment of the present invention, the concentration of the dilute sulfuric acid may be 1.5 mol / L, 2 mol / L, 2.5 mol / L or 3 mol / L.

[0043] In the present invention, the liquid-to-solid ratio of the leachate to the alkali metal sulfide is 1000mL:1-4g. In a specific embodiment of the present invention, the liquid-to-solid ratio may be 1000mL:1g, 1000mL:2g, 1000mL:3g or 1000mL:4g; the alkali metal sulfide preferably includes sodium sulfide.

[0044] In the present invention, the temperature of the thiolation reaction is preferably 65-75°C. In a specific embodiment of the present invention, the temperature of the thiolation reaction may be 65°C, 68°C, 70°C, 72°C or 75°C. The time is preferably 2-4h. In a specific embodiment of the present invention, the time of the thiolation reaction may be 2h, 3h or 4h.

[0045] In the present invention, the equation of thiolation reaction is:

[0046] Na 2 MoO 4 +Na 2 S→Na 2 MoS 4 +Na 2 O

[0047] After the thiolation reaction, the present invention preferably allows the product obtained from the thiolation reaction to stand and separate to obtain an aqueous solution containing sodium tungstate and the first residual sodium molybdate.

[0048] In the present invention, the standing temperature is preferably 25-30° C., and the standing time is preferably 5 h.

[0049] After obtaining an aqueous solution containing sodium tungstate and the first residual sodium molybdate, the present invention mixes the aqueous solution with a copper salt solution to perform a precipitation reaction to obtain a copper molybdate precipitate and a reaction solution containing tungsten trioxide and the second residual sodium molybdate.

[0050] In the present invention, the volume ratio of the aqueous solution to the copper salt solution is preferably 5-7:1. In a specific embodiment of the present invention, the volume ratio may be 5:1, 5.5:1, 6:1, 6.5:1 or 7:1. The copper salt solution preferably includes a copper sulfate solution. The concentration of the copper sulfate solution is preferably 3-5 mol / L. In a specific embodiment of the present invention, the concentration of the copper sulfate solution may be 3 mol / L, 4 mol / L or 5 mol / L.

[0051] In the present invention, the temperature of the vulcanization reaction is preferably 25-30° C., and the time is preferably 1-2 h. In a specific embodiment of the present invention, the temperature of the vulcanization reaction can be 1 h, 1.5 h or 2 h.

[0052] In the present invention, copper sulfate reacts with sodium molybdate in the sulfidation reaction to generate copper molybdate precipitate. In addition, copper salt can also react with remaining sodium sulfide to generate copper sulfide precipitate.

[0053] In the present invention, the sulfidation reaction is preferably carried out under stirring conditions; the stirring speed is preferably 300 r / min.

[0054] After the sulfurization reaction, the present invention preferably allows the product obtained from the sulfurization reaction to stand and separate to obtain the molybdenum precipitate and a reaction solution containing tungsten trioxide and residual molybdenum.

[0055] In the present invention, the standing temperature is preferably 25-30° C., and the standing time is preferably 5 h.

[0056] After obtaining the molybdenum precipitate and the reaction solution containing tungsten trioxide and residual molybdenum, the present invention mixes the reaction solution with an extractant to extract the tungsten trioxide to obtain an extract.

[0057] In the present invention, the volume ratio of the reaction liquid to the extractant is preferably 3-4.5:1. In a specific embodiment of the present invention, the volume ratio of the reaction liquid to the extractant may be 3:1, 3.5:1, 4:1 or 4.5:1.

[0058] In terms of volume percentage, the extractant includes 5-7% methyl trioctyl ammonium chloride, 8-10% N1923, 5% sec-octanol and the balance kerosene.

[0059] In the present invention, the extraction temperature is preferably 25-30° C. and the extraction time is 10-15 min.

[0060] After obtaining the extract, the present invention mixes the extract with aqueous ammonia to perform back extraction, causing double decomposition reaction, and then crystallizes the obtained back extraction solution to obtain ammonium paratungstate.

[0061] In the present invention, the volume ratio of the extract to aqueous ammonia is preferably 5:2; the concentration of aqueous ammonia is preferably 6 mol / L.

[0062] In the present invention, the stripping temperature is preferably 25-30° C., and the stripping time is preferably 10-15 min.

[0063] In the present invention, the crystallization method is preferably evaporative crystallization; the evaporative crystallization is preferably carried out in a vacuum distillation device, the evaporative crystallization temperature is preferably 55° C., and the time is preferably 2.5 h.

[0064] Ammonium tungstate generates ammonium paratungstate after crystallization transformation.

[0065] The following is a detailed description of the method for recovering tungsten from tungsten waste catalyst crystals provided by the present invention in conjunction with the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0066] Example 1

[0067] Take 100g of tungsten waste catalyst crystals (composition: Na 2 O 63.57%, SO 3 16.77%, WO 3 12.67%, SiO 2 2.57%, MoO 3 0.5%,Al 2 O 3 1.05%, CaO 0.66% and other impurities), crushed to 5μm with a grinding mortar, added to 300g pure water for aqueous leaching at a liquid-to-solid ratio of 3:1, controlled the reaction temperature to 65℃, and the leaching time to 4h. Take 200mL of the leached solution after filtration, adjust the pH value of the solution to 7 with 1mol / L dilute sulfuric acid, add 0.2g of sodium sulfide (control the concentration of free sulfide ions in the solution after sulfidation to be above 1g / L), control the reaction temperature to 65℃, the reaction time to 4h, let it stand for 5h after sulfidation, take 100mL of the sulfided solution at room temperature, add 20mL of 3mol / L copper sulfate solution, set the speed to 300r / min, stir well for 1h, and let it stand for 5h. 50mL of the liquid after standing was taken as the aqueous phase, 5% methyl trioctyl ammonium chloride, 10% N1923, 5% octanol, and 80% kerosene (by volume fraction) were used as the organic phase, O / A was 1:3, the extraction time was 10min, and ammonia water was used as the stripping agent (the volume ratio of the extracted extract (i.e., the organic phase) to ammonia water was 5:2, and the concentration of ammonia water was 6mol / L), and the loaded organic phase was stripped for 10min. After the stripping was completed, the stripping solution was evaporated and crystallized in a vacuum distillation device at a temperature of 55°C for 2.5h to obtain ammonium paratungstate. The final tungsten recovery rate was 94.8%, and the molybdenum removal rate was 90.4%.

[0068] The calculation method of molybdenum removal rate is:

[0069] 1-(Mo concentration in raffinate × raffinate volume) / (Mo concentration in feed solution × feed solution volume) × 100%

[0070] Example 2

[0071] Take 100g of tungsten waste catalyst crystals (with the same composition as in Example 1), crush them to 10μm with a grinding mortar, add them to 300g of pure water for aqueous leaching at a liquid-solid ratio of 3:1, control the reaction temperature to 70°C, and the leaching time to 3h. Take 200mL of the leached solution after suction filtration, adjust the pH value of the solution to 7 with dilute sulfuric acid with a concentration of 1mol / L, add 0.3g of sodium sulfide (control the concentration of free sulfide ions in the solution after sulfidation to be maintained at above 1.5g / L), control the reaction temperature to 70°C, the reaction time to 3h, let it stand for 5h after sulfidation, take 100mL of the sulfided solution at room temperature, add 17.5mL of copper sulfate solution with a concentration of 4mol / L, set the speed to 300r / min, stir well for 1.5h, and let it stand for 5h. 50mL of the liquid after standing was taken as the aqueous phase, 6% methyl trioctyl ammonium chloride, 9% N1923, 5% octanol, and 80% kerosene (by volume fraction) were used as the organic phase, O / A was 1:3, the extraction time was 10min, and ammonia water was used as the stripping agent (the volume ratio of the extracted extract (i.e., the organic phase) to ammonia water was 5:2, and the concentration of ammonia water was 6mol / L), and the loaded organic phase was stripped for 10min. After the stripping was completed, the stripping solution was evaporated and crystallized in a vacuum distillation device at a temperature of 55°C for 2.5h to obtain ammonium paratungstate. The final tungsten recovery rate was 96.7%, and the molybdenum removal rate was 92.6%.

[0072] Example 3

[0073] Take 100g of tungsten waste catalyst crystals (the ingredients are the same as in Example 1), crush them to 15μm with a grinding mortar, add them to 300g of pure water for aqueous leaching at a liquid-solid ratio of 3:1, control the reaction temperature to 75°C, and the leaching time to 2h. Take 200mL of the leached solution after suction filtration, adjust the pH value of the solution to 7 with dilute sulfuric acid with a concentration of 1mol / L, add 0.4g of sodium sulfide (control the concentration of free sulfide ions in the solution after sulfidation to be maintained at above 2g / L), control the reaction temperature to 75°C, the reaction time to 2h, and let it stand for 5h after sulfidation. Take 100mL of the sulfided solution at room temperature, add 15mL of 5mol / L copper sulfate solution, set the speed to 300r / min, stir well for 2h, and let it stand for 5h. Take 50mL of the liquid after standing as the aqueous phase, 7% methyl trioctyl ammonium chloride, 8% N1923, 5% octanol, 80% kerosene (by volume fraction) as the organic phase, O / A is 1:3, the extraction time is 10min, and ammonia water is used as the stripping agent (the volume ratio of the extracted extract (i.e., the organic phase) to ammonia water is 5:2, and the concentration of ammonia water is 6mol / L), and the loaded organic phase is stripped for 10min. After the stripping is completed, the stripping solution is evaporated and crystallized in a vacuum distillation device at a temperature of 55°C for 2.5h to obtain ammonium paratungstate. The final tungsten recovery rate is 93.5%, and the molybdenum removal rate is 91.1%.

[0074] Comparative Example 1

[0075] Take 100g of tungsten waste catalyst crystals (composition (same as Example 1)), crush them to 10μm with a grinding mortar, add them to 300g of pure water for aqueous leaching at a liquid-solid ratio of 3:1, control the reaction temperature to 70°C, and the leaching time to 3h. Take 200mL of the leached solution after suction filtration, adjust the pH value of the solution to 7 with dilute sulfuric acid with a concentration of 1mol / L, add 0.3g of sodium sulfide (control the concentration of free sulfide ions in the solution after sulfidation to be maintained at above 1.5g / L), control the reaction temperature to 70°C, the reaction time to 3h, and let it stand for 5h after sulfidation. Take 100mL of the sulfided solution at room temperature, add 17.5mL of copper sulfate solution with a concentration of 4mol / L, set the speed to 300r / min, stir well for 1.5h, and let it stand for 5h. Take 50mL of the liquid after standing as the aqueous phase, 10% N1923, 5% octanol, and 85% kerosene (by volume fraction) as the organic phase, O / A is 1:3, the extraction time is 10min, and ammonia water is used as the stripping agent (the volume ratio of the extracted extract (i.e., the organic phase) to ammonia water is 5:2, and the concentration of ammonia water is 6mol / L), and the loaded organic phase is stripped for 10min. After the stripping is completed, the stripping solution is vacuum distilled at a temperature of 55°C to obtain ammonium paratungstate. The final tungsten recovery rate is 89.17%, and the molybdenum removal rate is 83.05%.

[0076] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for recovering tungsten from tungsten waste catalyst crystals, characterized in that: The following steps are involved: The tungsten waste catalyst crystals are mixed with water and then leached to obtain a leaching solution containing sodium tungstate and sodium molybdate; The leachate is mixed with an acid and an alkali metal sulfide to carry out a thiolation reaction to obtain a Na2MoO4 precipitate and an aqueous solution containing sodium tungstate and a first residual sodium molybdate; The aqueous solution is mixed with a copper salt solution to perform a precipitation reaction to obtain a copper molybdate precipitate and a reaction solution containing sodium tungstate and a second residual sodium molybdate; The reaction solution is mixed with an extractant to extract sodium tungstate to obtain an extract; The extractant comprises the following components by volume fraction: 5-7% methyl trioctyl ammonium chloride, 8-10% N1923, 5% sec-octanol and the balance kerosene; The extract is mixed with aqueous ammonia for stripping, a double decomposition reaction occurs, and then the stripping solution obtained is crystallized to obtain ammonium paratungstate.

2. The recycling method according to claim 1, characterized in that: Calculated by mass fraction of oxides, the tungsten waste catalyst crystals include Na2O 60-70%, WO3 10-14%, SO3 15-20%, SiO2 0.5-3%, MoO3 0.2-0.8%, Al2O3 0.5-2%, CaO 0.5-1.5% and the remainder of impurities.

3. The recovery method according to claim 1 or 2, characterized in that: The leaching temperature is 65-75°C and the leaching time is 1-3h; The leaching is carried out under stirring conditions; the stirring speed is 280-500 r / min.

4. The recycling method according to claim 1, characterized in that: The acid includes dilute sulfuric acid; the concentration of the dilute sulfuric acid is 1.5-3 mol / L.

5. The recovery method according to claim 1 or 4, characterized in that: Mixing the leaching solution with acid and alkali metal sulfide comprises: mixing the leaching solution with acid, and then mixing the obtained solution with alkali metal sulfide; the pH value of the solution is 6.5-7.

5.

6. The recycling method according to claim 1, characterized in that: The alkali metal sulfide includes sodium sulfide.

7. The recycling method according to claim 1 or 6, characterized in that: The liquid-to-solid ratio of the leaching solution to the alkali metal sulfide is 1000 mL: 1-4 g.

8. The recycling method according to claim 1, characterized in that: The copper salt solution includes a copper sulfate solution; the concentration of the copper sulfate solution is 3-5 mol / L.

9. The recycling method according to claim 1 or 8, characterized in that: The volume ratio of the aqueous solution to the copper salt solution is 5-7:

1.

10. The recycling method according to claim 1, characterized in that: The volume ratio of the reaction solution to the extractant is 3-4.5:1; The extraction temperature is 25-30°C and the extraction time is 10-15 minutes.