Method for treating vanadium-containing waste liquid in a laboratory

Abstract

The application discloses a kind of laboratory vanadium-containing waste liquid processing methods, belong to sewage treatment field.The specific steps include: waste liquid is concentrated after adding H2O2 reaction, adjust pH value and precipitate iron, chromium, titanium in turn, then generate NH4VO3 crystal and ammonium magnesium phosphate crystal by adjusting pH value and adding crystal seed, finally adjust pH value and distill ammonia water to prepare ammonium sulfate, residual liquid is evaporated to obtain Na2SO4.The application realizes the gradient recovery of vanadium, phosphorus and sodium elements by multistage pH control and directional crystallization process, the vanadium recovery rate of this method is >82%, the phosphorus recovery rate is >84%, which can effectively solve the technical problems of incomplete recovery of vanadium and phosphorus, non-resource utilization of valuable elements and non-compliance of waste liquid and waste gas environmental protection in existing laboratory vanadium-containing waste liquid treatment methods.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment, specifically relating to a method for treating vanadium-containing waste liquid in laboratories. Background Technology

[0002] Vanadium and its compounds are key industrial raw materials, widely used in alloy manufacturing, catalyst preparation, and special materials. Vanadium-containing wastewater generated during the production and testing of vanadium products is highly acidic and contains tetravalent vanadium, iron ions, phosphate, and sulfate. Direct discharge of this wastewater not only wastes vanadium resources but also causes environmental pollution due to the high concentrations of heavy metals and acidic substances.

[0003] In recent years, to achieve the harmless treatment and resource utilization of vanadium-containing wastewater, researchers have developed various treatment processes, including precipitation, solvent extraction, ion exchange, electrolysis, adsorption, and biological methods. However, existing technologies have many limitations: precipitation, while simple in equipment, often focuses on the single recovery of vanadium, neglecting the utilization value of other components; ion exchange and adsorption, while capable of separating multiple components, have stringent equipment requirements and high operating costs. Furthermore, these methods are mostly designed for industrial vanadium-containing wastewater, while laboratory vanadium-containing wastewater differs significantly from industrial wastewater, exhibiting characteristics such as high-concentration sulfuric acid systems, coexistence of multiple vanadium valence states, and ammonium salt enrichment. This makes traditional industrial vanadium precipitation processes prone to impurity co-precipitation, affecting product purity.

[0004] Currently, laboratory wastewater treatment mainly employs centralized disposal after neutralization, failing to achieve targeted recovery of elements such as vanadium and phosphorus, resulting in resource waste. Some processes that directly precipitate vanadium suffer from high acid and alkali consumption, incomplete heavy metal removal, and fail to simultaneously address the recovery of sodium sulfate byproducts and the control of ammonia emissions. Existing technologies struggle to effectively recover valuable elements and ensure that wastewater and exhaust gases meet environmental protection requirements when treating vanadium-containing laboratory wastewater.

[0005] Therefore, there is an urgent need to develop a multi-element synergistic recovery method adapted to the characteristics of laboratory waste liquid, so as to achieve efficient separation of vanadium and phosphorus and resource utilization of sulfate. Summary of the Invention

[0006] The technical problem to be solved by this invention is that existing laboratory methods for treating vanadium-containing waste liquid suffer from incomplete recovery of vanadium and phosphorus, lack of resource utilization of valuable elements, and failure to meet environmental protection standards for waste liquid and waste gas.

[0007] To achieve the above-mentioned objectives, the technical solution adopted in this application is as follows:

[0008] In a first aspect, the present invention provides a method for treating vanadium-containing waste liquid in a laboratory, comprising the following steps:

[0009] S1. The vanadium-containing waste liquid in the laboratory is concentrated to 1 / 3 to 1 / 2.5 of its original volume; then, 30% H2O2 is added. The vanadium content in the laboratory waste liquid... 4+ The molar ratio of H2O2 to H2O2 is 1:0.5~1.2; the reaction is stirred at room temperature at a stirring rate of 140~160 rpm until V in the solution. 4+ Completely converted to V 5+ Stop stirring when the solution turns orange-red, and you will get solution 1.

[0010] The vanadium-containing waste liquid in the laboratory has a pH < 0, and its main ionic component is V. 4+ 3.0~3.5g / L, Na + 3.0~3.5g / L, Fe 3+ 1.0~2.0g / L, Ti 4+ 0.003~0.006g / L, Cr 3+ 0.15~0.30g / L, PO4 3- 11.0~13.0g / L, NH4 + 3.0~4.0g / L, SO4 2- 320.0~340.0g / L.

[0011] S2. Adjust the pH of solution 1 to 1.0-2.0 using 5 mol / L NaOH. Heat and stir the solution in a water bath at 60-65°C at a stirring rate of 140-160 rpm until Fe2+ is present in the solution. 3+ Complete precipitation and solid-liquid separation yielded Fe(OH)3 precipitate and solution 2.

[0012] S3. Adjust the pH of solution 2 to 3.5-4.5 using 5 mol / L NaOH. Add polyacrylamide (PAM) as a coagulant aid at a rate of 2 g / L for every 1 L of unconcentrated vanadium-containing laboratory waste liquid treated up to step S3. Heat and stir the solution in a water bath at 60-65°C at a stirring speed of 140-160 rpm until the Cr content in the solution decreases. 3+ and Ti 4+ Complete precipitation and solid-liquid separation yielded a mixed precipitate of Cr(OH)3 and TiO(OH)2 and a solution 3.

[0013] S4. Adjust the pH of solution 3 to 7.0-8.0 using 5 mol / L NaOH, and add NH4VO3 seed crystals at a rate of 0.1% (w / v); heat and stir the reaction in a water bath at 80-85℃ at a stirring speed of 140-160 rpm until NH4 in the solution is reduced. + With V5+ The reaction is complete to produce NH4VO3; then the temperature is lowered to 30~25℃ at a cooling rate of 0.5℃ / min and aged for 1~2 hours, followed by solid-liquid separation to obtain NH4VO3 crystals and solution 4.

[0014] S5. Adjust the pH of solution 4 to 9.0-10.0 using 5 mol / L NaOH. Add 9-10 mL / L of saturated MgCl2 solution to the vanadium-containing laboratory waste liquid (i.e., for every 1 L of unconcentrated vanadium-containing laboratory waste liquid, add 9-10 mL of saturated MgCl2 solution after processing to step S5). Heat and stir the reaction in a water bath at 45-55℃ at a stirring speed of 140-160 rpm until the Mg content in the solution increases. 2+ With PO4 3- Stop stirring when the reaction is complete, the solution becomes turbid and forms fine white crystals; then let it mature for 4-5 hours, and separate the solid and liquid to obtain magnesium ammonium phosphate crystals and solution 5.

[0015] S6. The pH of solution 5 is adjusted to ≥12.0 using 5 mol / L NaOH. Ammonia water and distilled water are obtained by distillation and condensation. The ammonia water is absorbed by 10% sulfuric acid to produce ammonium sulfate. The residue after distillation is further evaporated to dryness to obtain Na2SO4.

[0016] The beneficial effects of this invention are as follows: This invention provides a treatment method for vanadium-containing laboratory waste liquid, which is rich in high concentrations of sulfate and ammonium ions, providing a good foundation for resource utilization. Furthermore, the vanadium concentration in this waste liquid exceeds 3.30 g / L, far exceeding the industrial-grade ammonium metavanadate vanadium concentration standard, thus possessing significant recovery value. This invention achieves the tiered recovery of vanadium, phosphorus, and sodium elements through multi-stage pH control and directional crystallization processes. Vanadium is recovered as ammonium metavanadate (recovery rate > 82%), phosphorus is converted into magnesium ammonium phosphate fertilizer (recovery rate > 84%), and sulfate ions are enriched as sodium sulfate. Compared with traditional single-target recovery processes, this invention simultaneously achieves vanadium-phosphorus separation and ammonia nitrogen fixation during waste liquid treatment, avoiding resource waste.

[0017] Compared to traditional neutralization methods, this invention employs a graded pH control strategy to selectively precipitate different metal ions based on their varying hydroxide solubility products. This reduces acid and alkali dosage while ensuring high heavy metal removal rates, significantly lowering treatment costs. The entire process utilizes atmospheric pressure evaporation and precipitation separation technology, avoiding the need for high-temperature, high-pressure equipment. Furthermore, precise control of reaction conditions suppresses ammonia escape, ultimately achieving full resource recovery of valuable elements in the wastewater and near-zero pollutant emissions. Detailed Implementation

[0018] To make the technical problems, technical solutions, and beneficial effects of this application clearer, the following detailed description is provided in conjunction with the embodiments. Those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise defined, all technical terms used herein have the same meaning as understood by those skilled in the art. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0019] The method described in this invention is used to treat vanadium-containing waste liquid in the laboratory. This embodiment is performed in the laboratory. When handling concentrated acids / alkalis, anti-corrosion gloves and goggles are worn, and H2O2 is added dropwise in a fume hood. The reagents used in this embodiment are: 1) 5 mol / L NaOH solution; 2) 30% H2O2; 3) polyacrylamide (PAM); 4) NH4VO3 seed crystals; 5) saturated MgCl2 solution (prepared by dissolving 23.9 g MgCl2·6H2O in 9.5 ml deionized water); 6) 10% sulfuric acid; 7) 10% KSCN.

[0020] The main ionic components of the laboratory vanadium-containing waste liquid (pH<0) used in Examples 1 and 2 are shown in Table 1.

[0021] Table 1. Main ionic components of vanadium-containing waste liquid (g / L)

[0022]

[0023] Example 1: Treatment of vanadium-containing waste liquid in the laboratory, including the following steps:

[0024] (1) Take 1 L of laboratory vanadium-containing waste liquid with the composition shown in Table 1 and concentrate it in four portions on a 250 mL rotary evaporator. To avoid direct heating causing bumping, the temperature should be slowly increased to 60 °C and concentrated under reduced pressure to 1 / 3 of the liquid volume, finally obtaining 350 mL of concentrated waste liquid. Transfer the concentrated waste liquid to a 500 mL glass beaker and cool to room temperature.

[0025] (2) Slowly add 8.0 mL of 30% H2O2 using a constant pressure dropping funnel, and stir the mixture at 150 rpm for 30 minutes at room temperature. The solution color will change from blue-green (V) 4+ ) turns pale yellow (V 5+ When the number of bubbles decreases significantly, it indicates that the reaction is approaching completion, meaning that the concentration of V in the solution has decreased. 4+ Completely converted to V 5+ Stop stirring when the solution turns orange-red to obtain solution 1.

[0026] (3) Transfer solution 1 to a 500 mL beaker and add 15.8 mL of NaOH solution in portions, gradually adjusting the pH of solution 1 to 2.0, ensuring the pH value is precisely controlled within the range of 2.0 ± 0.1 to avoid co-precipitation of V. Place the beaker in a 60℃ water bath and heat, stirring continuously for 30 minutes. At this time, flocculent reddish-brown precipitate will form in the solution. To verify Fe 3+ To check if the removal is complete, take one drop of the supernatant and add one drop of KSCN solution. If no red color appears, it indicates that Fe... 3+ The precipitate had completely settled. Filtration was then performed, yielding 2.8 g of Fe(OH)₃ precipitate and solution 2.

[0027] (4) Transfer solution 2 to a 500 mL beaker, add 10 mL of NaOH solution, and adjust the pH of solution 2 to 4.0. Add 2 g of polyacrylamide (PAM) as a coagulant to promote the coagulation of Ti. 4+ and Cr 3+ The precipitate was formed. The beaker was placed in a 60°C water bath and heated with continuous stirring for 1 hour. This was to verify the precipitation of Cr. 3+ To check if chromium has been completely removed, place one drop of the supernatant on chromium qualitative test paper. If there is no color change, it indicates that chromium has been completely removed. 3+ Complete precipitation has occurred. Filtering yielded 0.21 g of a mixed precipitate of Cr(OH)3 and TiO(OH)2, and a solution 3 with a pH of approximately 6 (nearly neutral).

[0028] (5) Transfer solution 3 to a 500 mL beaker and heat it to 85°C in a constant temperature water bath. Add 1 mL of NaOH solution to adjust the pH of solution 3 to 7.5. Then add 0.1% (w / v) of NH4VO3 seed crystals to promote the growth of NH4. + With V 5+ The reaction proceeded completely to produce NH4VO3. The solution was slowly cooled to 25°C at a cooling rate of 0.5°C / min and aged at this temperature for 2 hours. Afterwards, the solution was filtered to obtain an NH4VO3 crystal filter cake and solution 4. The filter cake was placed in a vacuum drying oven and dried at 60°C, finally yielding 6.4 g of yellow NH4VO3 crystals.

[0029] (6) Transfer solution 4 to a 500 mL beaker and heat it to 50°C in a constant temperature water bath. Add 1 mL of NaOH solution to adjust the pH of solution 4 to 9.5 to prevent local supersaturation and colloid formation. Then slowly add 9.5 mL of saturated MgCl2 solution and stir continuously for 30 minutes. At this time, the solution will become turbid and form fine white crystals. After stopping stirring, let the solution stand for 4 hours to mature. After filtration, 24.8 g of magnesium ammonium phosphate crystals (as struvite fertilizer) and solution 5 are obtained.

[0030] (7) Transfer solution 5 to a glass distillation apparatus, add 2.5 mL of NaOH solution, and adjust the pH of solution 5 to 12.0. Perform atmospheric distillation, cool, and collect the ammonia and distilled water. Absorb the collected ammonia with sulfuric acid to prepare ammonium sulfate. Continue to evaporate the residue after distillation to dryness, finally obtaining 325.66 g of Na2SO4.

[0031] In Example 1, the vanadium recovery rate reached 83.4%, and the phosphorus recovery rate reached 84.9%. The generated metavanadic acid, phosphate fertilizer, and Na₂SO₄ all have significant economic value. Furthermore, the distilled water can be recycled and reused, and the entire process achieves near-zero wastewater discharge, fully complying with environmental protection requirements.

[0032] Example 2: Treatment of vanadium-containing waste liquid in the laboratory, including the following steps:

[0033] (1) Take 1 L of laboratory vanadium-containing waste liquid with the composition shown in Table 1 and concentrate it in four portions on a 250 mL rotary evaporator. To avoid direct heating causing bumping, the temperature should be slowly increased to 60 °C and concentrated under reduced pressure to 1 / 3 of the liquid volume, finally obtaining 340 mL of concentrated waste liquid. Transfer the concentrated waste liquid to a 500 mL glass beaker and cool to room temperature.

[0034] (2) Slowly add 4.0 mL of 30% H2O2 using a constant pressure dropping funnel, and stir the mixture at 150 rpm for 30 minutes at room temperature. The solution color will change from blue-green (V) 4+ ) turns pale yellow (V 5+ When the number of bubbles decreases significantly, it indicates that the reaction is approaching completion, meaning that the concentration of V in the solution has decreased. 4+ Completely converted to V 5+ Stop stirring when the solution turns orange-red to obtain solution 1.

[0035] (3) Transfer solution 1 to a 500 mL beaker and add 17.2 mL of NaOH solution in portions, gradually adjusting the pH of solution 1 to 2.0, ensuring the pH value is precisely controlled within the range of 2.0 ± 0.1 to avoid co-precipitation of V. Place the beaker in a 60℃ water bath and heat, stirring continuously for 30 minutes. At this time, flocculent reddish-brown precipitate will form in the solution. To verify Fe 3+ To check if the removal is complete, take one drop of the supernatant and add one drop of KSCN solution. If no red color appears, it indicates that Fe... 3+ The precipitate had completely settled. Filtration was then performed, yielding 2.9 g of Fe(OH)₃ precipitate and solution 2.

[0036] (4) Transfer solution 2 to a 500 mL beaker, add 9 mL of NaOH solution, and adjust the pH of solution 2 to 4.0. Add 2 g of polyacrylamide (PAM) as a coagulant to promote the coagulation of Ti. 4+ and Cr 3+ The precipitate was formed. The beaker was placed in a 60°C water bath and heated with continuous stirring for 1 hour. This was to verify the precipitation of Cr. 3+ To check if chromium has been completely removed, place one drop of the supernatant on chromium qualitative test paper. If there is no color change, it indicates that chromium has been completely removed. 3+ Complete precipitation has occurred. Filtration was performed to obtain 0.35 g of a mixed precipitate of Cr(OH)3 and TiO(OH)2, and a solution 3 with a pH of approximately 6 (nearly neutral).

[0037] (5) Transfer solution 3 to a 500 mL beaker and heat it to 85°C in a constant temperature water bath. Add 1 mL of NaOH solution to adjust the pH of solution 3 to 7.5. Then add 0.1% (w / v) of NH4VO3 seed crystals to promote the growth of NH4. + With V 5+ The reaction proceeded completely to produce NH4VO3. The solution was slowly cooled to 25°C at a cooling rate of 0.5°C / min and aged at this temperature for 2 hours. Afterwards, the solution was filtered to obtain an NH4VO3 crystal filter cake and solution 4. The filter cake was placed in a vacuum drying oven and dried at 60°C, finally yielding 6.5 g of yellow NH4VO3 crystals.

[0038] (6) Transfer solution 4 to a 500 mL beaker and heat it to 50°C in a constant temperature water bath. Add 1 mL of NaOH solution to adjust the pH of solution 4 to 9.5 to prevent local supersaturation and colloid formation. Then slowly add 9.0 mL of saturated MgCl2 solution and stir continuously for 30 minutes. At this time, the solution will become turbid and form fine white crystals. After stopping stirring, let the solution stand for 4 hours to mature. After filtration, 15.8 g of magnesium ammonium phosphate crystals (as struvite fertilizer) and solution 5 are obtained.

[0039] (7) Transfer solution 5 to a glass distillation apparatus, add 3.0 mL of NaOH solution, and adjust the pH of solution 5 to 13.0. Perform atmospheric distillation, cool, and collect the ammonia water and distilled water. Absorb the collected ammonia water with sulfuric acid to prepare ammonium sulfate. Continue to evaporate the residue after distillation to dryness, finally obtaining 384.6 g of Na2SO4.

[0040] In Example 2, the vanadium recovery rate was 82.7%, and the phosphorus recovery rate was increased to 88.1%. Similarly, the generated metavanadic acid, phosphate fertilizer, and Na₂SO₄ all have high economic value. Distilled water can also be recycled and reused, and the entire process achieves near-zero wastewater discharge, meeting environmental protection requirements.

Claims

1. A method for treating vanadium-containing waste liquid in a laboratory, characterized in that, Includes the following steps: S1. The vanadium-containing waste liquid in the laboratory is concentrated and then reacted with H2O2 to obtain solution 1; S2. Adjust the pH of solution 1 to 1.0~2.0, heat the reaction, separate the solid and liquid, and obtain Fe(OH)3 precipitate and solution 2; S3. Adjust the pH of solution 2 to 3.5~4.5, add coagulant, heat the reaction, and separate the solid and liquid to obtain a mixed precipitate of Cr(OH)3 and TiO(OH)2 and solution 3; S4. Adjust the pH of solution 3 to 7.0~8.0, add NH4VO3 seed crystals, heat to react, cool and age, and separate the solid and liquid to obtain NH4VO3 crystals and solution 4; S5. Adjust the pH of solution 4 to 9.0~10.0, add saturated MgCl2 solution, heat to react, ripen, separate solid and liquid to obtain magnesium ammonium phosphate crystals and solution 5; S6. Adjust the pH of solution 5 to ≥ 12.0, and obtain ammonia water and distilled water by distillation and condensation. The ammonia water is absorbed by sulfuric acid to produce ammonium sulfate. The residue after distillation is further evaporated to dryness to obtain Na2SO4.

2. The method for treating vanadium-containing waste liquid in the laboratory according to claim 1, characterized in that: The vanadium-containing waste liquid from the laboratory has a pH < 0, and its main ionic component is V. 4+ 3.0~3.5g / L, Na + 3.0~3.5g / L, Fe 3+ 1.0~2.0g / L, Ti 4+ 0.003~0.006g / L, Cr 3+ 0.15~0.30g / L, PO4 3- 11.0~13.0g / L, NH4 + 3.0~4.0g / L, SO4 2- 320.0~340.0g / L.

3. The method for treating vanadium-containing waste liquid in the laboratory according to claim 1, characterized in that: In step S1, V in the vanadium-containing waste liquid in the laboratory 4+ The molar ratio of H2O2 to H2O2 is 1:0.5~1.2; In step S3, the amount of coagulant added is 2 g / L of vanadium-containing waste liquid in the laboratory; In step S4, the amount of NH4VO3 seed crystals added is 0.1% w / v; In step S5, the amount of saturated MgCl2 solution added is 9~10 mL / L of vanadium-containing waste liquid from the laboratory.

4. The method for treating vanadium-containing waste liquid in the laboratory according to claim 1, characterized in that: In step S1, the mass concentration of H2O2 is 30%; In step S3, the coagulant is polyacrylamide; In step S6, the mass concentration of the sulfuric acid is 10%; In steps S1 to S6, the pH of the solution is adjusted using NaOH with a concentration of 5 mol / L.

5. The method for treating vanadium-containing waste liquid in the laboratory according to claim 1, characterized in that: In step S1, the concentration process involves concentrating 1L of vanadium-containing laboratory waste liquid to 1 / 3 to 1 / 2.5 of its original volume. In step S1, after adding H2O2, the mixture is stirred at room temperature until the solution reaches V. 4+ Completely converted to V 5+ Stop stirring when the solution turns orange-red.

6. The method for treating vanadium-containing laboratory waste liquid according to claim 1, characterized in that: In step S2, after adjusting the pH, the mixture is heated and stirred in a water bath at 60-65°C until Fe in the solution reaches a certain concentration. 3+ Complete sedimentation.

7. The method for treating vanadium-containing laboratory waste liquid according to claim 1, characterized in that: In step S3, after adding the coagulant aid, the mixture is heated and stirred in a water bath at 60-65°C until the Cr content in the solution reaches a certain level. 3+ and Ti 4+ Complete sedimentation.

8. The method for treating vanadium-containing laboratory waste liquid according to claim 1, characterized in that: In step S4, after adding NH4VO3 seed crystals, the mixture is heated and stirred in a water bath at 80-85°C until the solution contains NH4. + With V 5+ The reaction completely produces NH4VO3; In step S4, after the heating reaction is completed, the temperature is lowered to 30~25℃ at a cooling rate of 0.5℃ / min and aged for 1~2 hours.

9. The method for treating vanadium-containing laboratory waste liquid according to claim 1, characterized in that: In step S5, after adding a saturated MgCl2 solution, the mixture is heated and stirred in a water bath at 45-55°C until the Mg content in the solution increases. 2+ With PO4 3- Stop stirring when the reaction is complete, the solution becomes cloudy and forms fine white crystals; In step S5, after the heating reaction is complete, allow it to mature for 4-5 hours.

10. The method for treating vanadium-containing laboratory waste liquid according to any one of claims 5 to 9, characterized in that: The stirring speed is 140~160 rpm.

Images