A method for resourceful treatment of wastewater in a short process preparation process of calcium vanadium electrolyte

Abstract

The present application relates to the technical field of hydrometallurgy and wastewater resource utilization, and particularly relates to a resource utilization treatment method for wastewater in a short-process preparation process of calcium vanadium electrolyte, comprising the following steps: step 1, adjusting the pH value of waste liquid, using an extractant to perform collaborative extraction on vanadium and aluminum in the wastewater, so that the vanadium and aluminum enter an organic phase, while manganese, magnesium and sodium remain in the raffinate water phase, and the extractant is an acidic phosphorus extractant; step 2, after water washing of the loaded organic phase, gradient stripping is performed, the loaded organic phase is first stripped by using a medium-concentration acid stripping solution, selective stripping of tetravalent vanadium is performed, and a vanadium-rich stripping solution is obtained; and then the remaining aluminum in the organic phase is stripped by using a medium-high-concentration acid stripping solution, and an aluminum-rich stripping solution is obtained; and step 3, the vanadium-rich stripping solution is sent to an extraction process for concentration and reuse; and the aluminum-rich stripping solution is subjected to pH adjustment and precipitation to obtain high-purity aluminum hydroxide.

Description

Technical Field

[0001] This invention relates to the field of hydrometallurgy and wastewater resource utilization technology, specifically to a resource utilization treatment method for wastewater from the short-process preparation of calcium vanadium electrolyte. Background Technology

[0002] The rapid development of vanadium redox flow batteries (VRFB) has generated a large amount of wastewater from electrolyte preparation. This wastewater has a complex composition: low vanadium concentration (<0.3 g / L) but high value, and also contains various metal ions such as aluminum, manganese, and magnesium, as well as high concentrations of sodium sulfate. Traditional treatment processes have the following limitations: 1. Neutralization precipitation method: This method involves adding alkaline solution to generate mixed hydroxide sludge, which is then landfilled as hazardous waste. This method results in significant resource waste, high disposal costs, and substantial environmental risks.

[0003] 2. Single element recovery: Only vanadium is recovered, while other valuable elements are not utilized, resulting in poor economic efficiency and high subsequent sludge treatment costs.

[0004] 3. The problem of stepwise precipitation: Due to Al 3+ Mn 2+ Mg 2+ The pH ranges for the precipitation of hydroxides of metal ions overlap (such as Al(OH)3 and Mn(OH)2), resulting in poor separation efficiency, low product purity, severe entrainment, and low recovery rate by traditional methods.

[0005] Patent CN113233569A proposes a method for rapidly removing manganese ions from wastewater and recovering precious metals using manganese-containing products. However, this patent only achieves the resource utilization of a single element and does not clearly address the removal efficiency and selectivity of other heavy metal ions in the wastewater.

[0006] Patent CN108046329A proposes a process for recovering magnesium and manganese from industrial wastewater, including steps such as wastewater element determination, manganese chloride precipitation, acidification and salt precipitation, vacuum distillation crystallization, and centrifugal drying. This process has potential and advantages in recovering specific metal elements and reducing pollution. However, the process is complex and energy-intensive, making it difficult to achieve economical and efficient comprehensive resource recovery. Summary of the Invention

[0007] The purpose of this invention is to provide a resource-based treatment method for wastewater from the short-process preparation of calcium-vanadium electrolyte, solving the technical problem in the prior art that it is impossible to economically and efficiently separate and recover all valuable metals from wastewater and achieve zero wastewater discharge.

[0008] This invention discloses a method for the resource-based treatment of wastewater from the short-process preparation of calcium-based vanadium electrolyte, comprising the following steps: Step 1: Adjust the pH value of the waste liquid and use an extractant to synergistically extract vanadium and aluminum from the wastewater, so that vanadium and aluminum enter the organic phase, while manganese, magnesium and sodium remain in the raffinate aqueous phase. The extractant is an acidic phosphorus extractant. Step 2: After washing the supported organic phase with water, gradient back-extraction is performed. First, the supported organic phase is back-extracted with a medium-concentration acid back-extraction solution to selectively back-extract tetravalent vanadium, resulting in a vanadium-rich back-extraction solution. Then, the remaining aluminum in the organic phase is back-extracted with a medium-to-high concentration acid back-extraction solution to obtain an aluminum-rich back-extraction solution. Step 3: Send the vanadium-rich back-extraction solution to the extraction process for concentration and reuse; adjust the pH of the aluminum-rich back-extraction solution to precipitate and obtain high-purity aluminum hydroxide.

[0009] Furthermore, the extractant includes acidic phosphorus extractants, diluents, and co-extractants.

[0010] Furthermore, the acidic phosphorus extractant is di(2-ethylhexyl) phosphate (P204) or trioctylphosphine oxide (P507); And / or, the co-extractant is one or more combinations of tributyl phosphate (TBP) and 2-octanol; And / or, the diluent is one or more combinations of sulfonated kerosene and No. 200 solvent oil; And / or, the volume ratio of the acidic phosphorus extractant to the diluent is 1:9 to 1:2.

[0011] Furthermore, the waste liquid mentioned in step 1 is the raffinate after extracting tetravalent vanadium with calcified acid leaching solution; And / or, the pH range of the adjusted waste liquid is 2.5 to 3.5.

[0012] Furthermore, the synergistic extraction conditions described in step 1 are as follows: the amount of extractant used and the oil-water ratio are flexibly adjusted according to the residual vanadium and aluminum content in the waste liquid during the staged testing. The oil-water ratio O / A = 1:7~25, the extraction time is 10~20 minutes of stirring, and the extraction temperature is 15~35℃.

[0013] Furthermore, the moderate concentration acid mentioned in step 2 is 1~2 mol / L; And / or, for medium to high concentrations of acid, the concentration is 3-6 mol / L; And / or, the back-extraction conditions are as follows: the amount of back-extractant used is flexibly adjusted according to the vanadium and aluminum content in the supported organic phase, the back-extraction time is 10-15 minutes of stirring, and the back-extraction temperature is 15-35℃.

[0014] Furthermore, the back-extraction ratio described in step 2 is O / A = 5~10:1.

[0015] And / or, the alkaline regulator added during the pH adjustment of the aluminum-rich back-extraction solution in step 3 is NaOH or ammonia water; And / or, the pH value of the aluminum-rich back-extraction solution is adjusted to 4.8~6.2.

[0016] Furthermore, it also includes: Step 4: Combine the remaining liquid after aluminum precipitation with the raffinate from Step 1. First, adjust the pH and aerate to precipitate manganese ions, then adjust the pH to precipitate magnesium ions. Step 5: Evaporate and crystallize the mother liquor after magnesium precipitation to recover anhydrous sodium sulfate; Step 6: Adjust the pH of the crystallized solution before discharging.

[0017] Furthermore, the precipitant added in step 4 to precipitate manganese ions is a carbonate.

[0018] And / or, the pH value is adjusted to 9.5~10.2 by precipitating manganese ions as described in step 4; And / or, the aeration intensity of the precipitated manganese ions in step 4 is 2-5 Nm. 3 / (m 2 ·h); And / or, the precipitant added in step 4 to precipitate magnesium ions is Na2CO3; And / or, the precipitated magnesium ions in step 4 adjust the pH value to ≥10.5.

[0019] Furthermore, and / or, the carbonate is Na2CO3, NaHCO3, or NaOH.

[0020] Furthermore, the evaporation and crystallization temperature in step 5 is 95~105℃.

[0021] Compared with the prior art, the beneficial effects of the present invention are: 1. By using synergistic extraction, vanadium and aluminum are efficiently co-extracted, effectively solving the problem of overlapping precipitation zones of aluminum and other metal ions, making them difficult to separate and recover. 2. The gradient back-extraction process enables high-purity separation and recovery of vanadium and aluminum, thereby increasing the added value of the product; 3. The stepwise precipitation strategy enables the sequential recovery of manganese and magnesium, with a simple process and flexible operation, thereby enhancing the resource utilization value of valuable metals. 4. No wastewater is discharged throughout the entire process. The introduced precipitant and alkaline regulator are ultimately recovered in the form of anhydrous sodium sulfate, realizing resource utilization and making it green and environmentally friendly. 5. High process integration and low operating cost, suitable for industrial promotion. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0023] Example 1 This embodiment discloses a method for resource-based treatment of wastewater from the short-process preparation of calcium-based vanadium electrolyte, comprising the following steps: Table 1. Content of major metal ions in calcified raffinate (mg / L)

[0024] Step 1: Take 10L of calcified raffinate with an initial pH of 1.8 and add liquid alkali to adjust the pH to 2.5; prepare the extraction organic phase by mixing P204 and sulfonated kerosene at a volume ratio of 15:85 and an oil-water ratio of O / A=1:15, stir for 15 minutes and extract, and separate the phases to obtain the loaded organic phase and the raffinate aqueous phase. Step 2: Wash the loaded organic phase twice with pure water. Mix a measured amount of 1 mol / L sulfuric acid solution with the loaded organic phase at an oil-water ratio of O / A = 5:1. Stir for 10 minutes. After separation, obtain a vanadium-rich back-extraction solution and an aluminum-rich organic phase. The vanadium-rich organic phase is directly returned to the extraction process section for vanadium concentration and recovery. Subsequently, mix a 3 mol / L hydrochloric acid solution with the organic phase at an oil-water ratio of O / A = 5:1. Stir for 10 minutes. After separation, obtain an aluminum-rich back-extraction solution and a blank organic phase. The blank organic phase is directly returned to Step 1 for recycling. Step 3: Add NaOH to the aluminum-rich back-extraction solution to adjust the pH to 6, stir and react for 15 minutes, filter to obtain aluminum hydroxide precipitate, and mix the remaining liquid with the raffinate water from step 1 to obtain the pre-manganese precipitation solution. Step 4: Add Na2CO3 to the pre-manganese precipitation solution to adjust its pH to 10, stir and apply 2 Nm3 / (m2·h) of aeration. After reacting for 30 minutes, filter to obtain hydrated manganese dioxide precipitate and aqueous phase; then add NaOH to adjust the pH of the aqueous phase to 11, and ensure that the pH of the reaction process is ≥10.5. Stir the reaction for 20 minutes, and filter to obtain magnesium hydroxide precipitate and magnesium precipitation mother liquor. Step 5: Evaporate and crystallize the magnesium precipitation mother liquor at a reaction temperature of 100℃ to obtain anhydrous sodium sulfate product. Meanwhile, the condensate can be directly recycled to the front-end dilution and conditioning process.

[0025] After the above treatment, the calcification raffinate produces no additional waste and achieves the resource utilization of valuable metals. The purity of hydrated manganese dioxide is ≥99% and the purity of magnesium hydroxide is ≥99%.

[0026] Example 2: Use the calcified extract from Table 1.

[0027] Step 1: Take 10L of calcified raffinate with an initial pH of 1.8 and add liquid alkali to adjust the pH to 2.5; prepare the extraction organic phase by mixing P204 and sulfonated kerosene at a volume ratio of 25:75 and an oil-water ratio of 1:10, stir for 15 minutes and extract, and separate the phases to obtain the loaded organic phase and the raffinate aqueous phase. Step 2: Measure a certain amount of 2 mol / L sulfuric acid solution at an oil-water ratio of 10:1 and mix it with the loaded organic phase. Stir for 15 minutes, and after separation, obtain vanadium-rich back-extraction solution and organic phase. Then, measure a 4 mol / L sulfuric acid solution at an oil-water ratio of 10:1 and mix it with the organic phase. Stir for 10 minutes, and after separation, obtain vanadium-rich back-extraction solution and blank organic phase. The blank organic phase is directly returned to Step 1 for recycling. Step 3: Add NaOH to the aluminum-rich back-extraction solution to adjust the pH to 5, stir and react for 25 minutes, filter to obtain aluminum hydroxide precipitate, and mix the remaining liquid with the raffinate water from step 1 to obtain the pre-manganese precipitation solution. Step 4: Add sodium carbonate to the pre-manganese precipitation solution to adjust its pH to 9.8, stir and apply 2 Nm³ / (m²·h) of aeration for 40 minutes, then filter to obtain hydrated manganese dioxide precipitate and aqueous phase; then add Na2CO3 to adjust the pH of the aqueous phase to 11.0, and ensure that the pH of the reaction process is ≥10.5, the reaction time is 20 minutes, and filter to obtain magnesium hydroxide precipitate and magnesium precipitation mother liquor; Step 5: Evaporate and crystallize the magnesium precipitation mother liquor at a reaction temperature of 100℃ to obtain anhydrous sodium sulfate product. At the same time, the condensate is directly recycled to the front-end dilution and conditioning process.

[0028] After the above treatment, the calcification raffinate produces no additional waste and achieves the resource utilization of valuable metals. The purity of hydrated manganese dioxide is ≥99% and the purity of magnesium hydroxide is ≥99%.

[0029] Example 3 The only change from Example 1 is that the pH of the calcified raffinate is adjusted to 3 in step 1. Within a predetermined range, adjusting the pH of the raffinate does not affect the final result.

[0030] Comparative Example 1 Use the calcified extract from Table 1.

[0031] Step 1: Take 10L of calcified raffinate with an initial pH of 1.8 and add liquid alkali to adjust the pH to 2.5; prepare the extraction organic phase by mixing P204 and sulfonated kerosene at a volume ratio of 15:85 and an oil-water ratio of O / A=1:15, stir for 15 minutes and extract, and separate the phases to obtain the loaded organic phase and the raffinate aqueous phase. Step 2: Wash the loaded organic phase twice with pure water. Mix a measured amount of 4 mol / L sulfuric acid solution with the loaded organic phase at an oil-water ratio of O / A = 5:1. Stir for 10 minutes. After separation, obtain a vanadium-rich back-extraction solution and an aluminum-rich organic phase. The vanadium-rich organic phase is directly returned to the extraction process section for vanadium concentration and recovery. Subsequently, mix a 1 mol / L hydrochloric acid solution with the organic phase at an oil-water ratio of O / A = 5:1. Stir for 10 minutes. After separation, obtain an aluminum-rich back-extraction solution and a blank organic phase. The blank organic phase is directly returned to Step 1 for recycling. Step 3: Add NaOH to the aluminum-rich back-extraction solution to adjust the pH to 6, stir and react for 15 minutes, filter to obtain aluminum hydroxide precipitate, and mix the remaining liquid with the raffinate water from step 1 to obtain the pre-manganese precipitation solution. Step 4: Add Na2CO3 to the pre-manganese precipitation solution to adjust its pH to 10, stir and apply 2 Nm3 / (m2·h) of aeration. After reacting for 30 minutes, filter to obtain hydrated manganese dioxide precipitate and aqueous phase; then add NaOH to adjust the pH of the aqueous phase to 11, and ensure that the pH of the reaction process is ≥10.5. Stir the reaction for 20 minutes, and filter to obtain magnesium hydroxide precipitate and magnesium precipitation mother liquor. Step 5: Evaporate and crystallize the magnesium precipitation mother liquor at a reaction temperature of 100℃ to obtain anhydrous sodium sulfate product. Meanwhile, the condensate can be directly recycled to the front-end dilution and conditioning process.

[0032] In step 2 of this comparative example, compared to Example 1, high-acidity sulfuric acid was used to back-extract tetravalent vanadium. As a result, tetravalent vanadium and aluminum ions were back-extracted together, and the aluminum ion concentration in the back-extraction solution was >220mg / l. This could not achieve the effect of precise vanadium-aluminum separation, thus affecting the recycling of vanadium and aluminum and failing to demonstrate the technical advantages of this patent.

[0033] Comparative Example 2 Use the calcified extract from Table 1.

[0034] Step 1: Take 10L of calcified raffinate with an initial pH of 1.8 and add liquid alkali to adjust the pH to 2.5; prepare the extraction organic phase by mixing P204 and sulfonated kerosene at a volume ratio of 15:85 and an oil-water ratio of O / A=1:15, stir for 15 minutes and extract, and separate the phases to obtain the loaded organic phase and the raffinate aqueous phase. Step 2: Wash the loaded organic phase twice with pure water. Mix a measured amount of 1 mol / L sulfuric acid solution with the loaded organic phase at an oil-water ratio of O / A = 5:1. Stir for 10 minutes. After separation, obtain a vanadium-rich back-extraction solution and an aluminum-rich organic phase. The vanadium-rich organic phase is directly returned to the extraction process section for vanadium concentration and recovery. Subsequently, mix a 3 mol / L hydrochloric acid solution with the organic phase at an oil-water ratio of O / A = 5:1. Stir for 10 minutes. After separation, obtain an aluminum-rich back-extraction solution and a blank organic phase. The blank organic phase is directly returned to Step 1 for recycling. Step 3: Add NaOH to the aluminum-rich back-extraction solution to adjust the pH to 6, stir and react for 15 minutes, filter to obtain aluminum hydroxide precipitate, and mix the remaining liquid with the raffinate water from step 1 to obtain the pre-manganese precipitation solution. Step 4: Add Na2CO3 to the pre-manganese precipitation solution to adjust its pH to 8, stir and apply 2 Nm³ / (m²·h) of aeration. After reacting for 30 minutes, filter to obtain hydrated manganese dioxide precipitate and aqueous phase; then add NaOH to adjust the pH of the aqueous phase to 10, and ensure that the pH of the reaction process is 10. Stir the reaction for 20 minutes, and filter to obtain magnesium hydroxide precipitate and magnesium precipitation mother liquor. Step 5: Evaporate and crystallize the magnesium precipitation mother liquor at a reaction temperature of 100℃ to obtain anhydrous sodium sulfate product. Meanwhile, the condensate can be directly recycled to the front-end dilution and conditioning process.

[0035] In this comparative example, changing the pH value of the solution during the manganese and magnesium precipitation processes resulted in incomplete precipitation of magnesium and manganese and two types of precipitates that could not be separated during the stage precipitation process. The magnesium hydroxide precipitate contained hydrated manganese dioxide with a purity of less than 98%. Due to the hydrated manganese dioxide precipitate mixed in, the value of the magnesium hydroxide by-product was greatly reduced.

[0036] Comparative Example 3 The only change from Example 1 was that in step 2, the first back-extraction of the vanadium-aluminum co-supported organic phase used a 3 mol / L hydrochloric acid back-extractant, while all other conditions remained unchanged. The results showed that co-extraction of vanadium and aluminum could not achieve effective separation of vanadium and aluminum. Furthermore, the use of hydrochloric acid in the first-stage back-extraction introduced additional chloride ions.

[0037] Comparative Example 4 Based on Example 1, the only change was adjusting the pH of the raffinate to 4 in step 1, while keeping all other conditions unchanged. The results showed that the entire process remained effective for the separation of vanadium and aluminum and the resource utilization of magnesium and manganese. However, the higher pH during the first extraction led to an increase in the single-stage efficiency of the P204 extraction stage, making it easier for other cations to be extracted. This reduced the efficiency of magnesium and manganese resource utilization and increased other metal impurities in the back-extraction solution, thus increasing the subsequent processing costs of tetravalent vanadium.

[0038] The above are the embodiments listed in this example. However, this example is not limited to the optional embodiments described above. Those skilled in the art can arbitrarily combine the above methods to obtain other various embodiments. Anyone can derive other various forms of embodiments based on the inspiration of this example. The above specific embodiments should not be construed as limiting the scope of protection of this example. The scope of protection of this example should be determined by the claims, and the specification can be used to interpret the claims.

Claims

1. A method for resource-based treatment of wastewater from a short-process preparation of calcium-vanadium electrolyte, characterized in that: Includes the following steps: Step 1: Adjust the pH value of the waste liquid and use an extractant to synergistically extract vanadium and aluminum from the wastewater, so that vanadium and aluminum enter the organic phase, while manganese, magnesium and sodium remain in the raffinate aqueous phase. The extractant is an acidic phosphorus extractant. Step 2: After washing the supported organic phase with water, gradient back-extraction is performed. First, the supported organic phase is back-extracted with a medium-concentration acid back-extraction solution to selectively back-extract tetravalent vanadium, resulting in a vanadium-rich back-extraction solution. Then, the remaining aluminum in the organic phase is back-extracted with a medium-to-high concentration acid back-extraction solution to obtain an aluminum-rich back-extraction solution. Step 3: Send the vanadium-rich back-extraction solution to the extraction process for concentration and reuse; adjust the pH of the aluminum-rich back-extraction solution to precipitate and obtain high-purity aluminum hydroxide.

2. The method for resource-based treatment of wastewater from the short-process preparation of calcium-vanadium electrolyte according to claim 1, characterized in that: The extractant includes acidic phosphorus extractants, diluents, and co-extractants.

3. The method for resource-based treatment of wastewater from the short-process preparation of calcium-vanadium electrolyte according to claim 2, characterized in that: The acidic phosphorus extractant is di(2-ethylhexyl) phosphate or trioctylphosphine oxide; And / or, the co-extractant is one or more combinations of tributyl phosphate and 2-octanol; And / or, the diluent is one or more combinations of sulfonated kerosene or No. 200 solvent oil; And / or, the volume ratio of the acidic phosphorus extractant to the diluent is 1:9 to 1:

2.

4. The method for resource-based treatment of wastewater from the short-process preparation of calcium-vanadium electrolyte according to claim 1, characterized in that: The waste liquid mentioned in step 1 is the raffinate after extracting tetravalent vanadium with calcified acid leaching solution; And / or, the pH range of the adjusted waste liquid is 2.5 to 3.

5.

5. The method for resource-based treatment of wastewater from the short-process preparation of calcium-vanadium electrolyte according to claim 1, characterized in that: The synergistic extraction conditions described in step 1 are as follows: the amount of extractant used and the oil-water ratio are flexibly adjusted according to the residual vanadium and aluminum content in the waste liquid during the stage-by-stage testing. The oil-water ratio O / A is 1:7~25, the extraction time is 10~20 minutes of stirring, and the extraction temperature is 15~35℃.

6. The method for resource-based treatment of wastewater from the short-process preparation of calcium-based vanadium electrolyte according to claim 1, characterized in that: The moderate concentration acid mentioned in step 2 is 1~2 mol / L; And / or, for medium to high concentrations of acid, the concentration is 3-6 mol / L; And / or, the back-extraction conditions are as follows: the amount of back-extractant used is flexibly adjusted according to the vanadium and aluminum content in the supported organic phase, the back-extraction time is 10-15 minutes of stirring, and the back-extraction temperature is 15-35℃.

7. The method for resource-based treatment of wastewater from the short-process preparation of calcium-based vanadium electrolyte according to claim 1, characterized in that: The back-extraction ratio described in step 2 is O / A = 5~10:1; And / or, the alkaline regulator added during the pH adjustment of the aluminum-rich back-extraction solution in step 3 is NaOH or ammonia water; And / or, the pH value of the aluminum-rich back-extraction solution is adjusted to 4.8~6.

2.

8. A method for resource-based treatment of wastewater from the short-process preparation of calcium-based vanadium electrolyte according to any one of claims 1-7, characterized in that: include: Step 4: Combine the remaining liquid after aluminum precipitation with the raffinate from Step 1. First, adjust the pH and aerate to precipitate manganese ions, then adjust the pH to precipitate magnesium ions. Step 5: Evaporate and crystallize the mother liquor after magnesium precipitation to recover anhydrous sodium sulfate; Step 6: Adjust the pH of the crystallized solution before discharging.

9. The method for resource-based treatment of wastewater from the short-process preparation of calcium-vanadium electrolyte according to claim 8, characterized in that: The precipitant added in step 4 to precipitate manganese ions is a carbonate; And / or, the pH value is adjusted to 9.5~10.2 by precipitating manganese ions as described in step 4; And / or, the aeration intensity of the precipitated manganese ions in step 4 is 2-5 Nm. 3 / (m 2 ·h); And / or, the precipitant added in step 4 to precipitate magnesium ions is Na2CO3; And / or, the precipitated magnesium ions in step 4 adjust the pH value to ≥10.

5.

10. The method for resource-based treatment of wastewater from the short-process preparation of calcium-based vanadium electrolyte according to claim 8, characterized in that: The evaporation and crystallization temperature in step 5 is 95~105℃.

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