Vanadium extraction wastewater full-amount recycling method of vanadium shale

Abstract

The present application relates to a kind of vanadium shale's vanadium extraction wastewater full-amount recycling method.The technical scheme is: vanadium shale powder is removed calcium with hydrochloric acid, and the calcium-removed vanadium shale and calcium-removed liquid are obtained;The calcium-removed liquid is mixed with the full amount of recycled vanadium extraction wastewater, and calcium chloride or sodium sulfate is added;Solid-liquid separation is carried out to obtain treated vanadium extraction wastewater and high-purity calcium sulfate by-product;Concentrated sulfuric acid, treated vanadium extraction wastewater and calcium fluoride are added to the calcium-removed vanadium shale, and solid-liquid separation is carried out to obtain leaching solution and leaching residue;The pH value of the leaching solution is adjusted with alkali, and solid-liquid separation is carried out to obtain neutralized leaching solution and neutralized residue;Sodium sulfite is added to the neutralized leaching solution to obtain the original extraction solution;The extraction agent, TBP and sulfonated kerosene are mixed to obtain the organic phase;Extraction is carried out to obtain raffinate and vanadium-rich liquid;Oxidizing agent is added to the vanadium-rich liquid, and the pH of the oxidized vanadium-rich liquid is adjusted;Solid-liquid separation is carried out to obtain ammonium polyvanadate and vanadium precipitation mother liquor.The present application realizes the full-amount recycling of vanadium extraction wastewater, and no secondary waste residue is generated, and high-purity by-products can be obtained.

Description

Technical Field

[0001] This invention belongs to the field of vanadium shale technology. Specifically, it relates to a method for the complete recycling of vanadium extraction wastewater from vanadium shale. Background Technology

[0002] Vanadium shale is a unique and advantageous vanadium resource in my country, with abundant reserves. Vanadium extraction from vanadium shale is currently an important approach for the development and utilization of high-performance vanadium products in my country. Raffinate and vanadium precipitation mother liquor are the main wastewaters from the vanadium extraction industry, characterized by large output and high NH4 content. + and SO4 2- The high plasma concentration and difficulty in treatment make the treatment of vanadium extraction wastewater, especially its recycling, a significant challenge in the vanadium extraction industry.

[0003] The patented technology, "A Method for Extracting Valuable Elements from Vanadium Shale" (CN 115807172A), employs a process of first-stage hydrochloric acid leaching for calcium and second-stage mixed acid leaching of vanadium and zinc using hydrochloric acid and sulfuric acid, to comprehensively recover various valuable elements from vanadium shale. While this method effectively reduces the viscosity of the slurry and increases the vanadium leaching rate, and lowers the pH value during vanadium extraction, thus reducing production costs, it does not consider the impact of recycling vanadium extraction wastewater on the vanadium extraction process, failing to achieve full utilization of industrial wastewater from vanadium extraction.

[0004] Jianying Huang et al. (Jianying Huang, Tao Liu, Yimin Zhang, and Pengcheng Hu. High-efficiency Internal Reuse of Raffinate in Vanadium (V) Extraction Industry and the Research of Intensifying Leaching Mechanism, [J]. Mineral Processing and Extractive Metallurgy Review, 2022, 5, 297-303) studied the effects of internal recycling of raffinate from a vanadium shale (CaO content 2.24 wt%) in Pengze, Jiangxi Province, on the leaching and extraction rates of roasted vanadium shale samples. The results showed that internal recycling of the raffinate had no negative impact on the vanadium leaching rate and could appropriately reduce the dosage of leaching aids CaF2 and H2SO4. This study indicates that during the internal recycling of the raffinate, the F content in the raffinate... -The cyclic enrichment does not inhibit the vanadium leaching rate, but this study only considered the effect of the raffinate on the roasted vanadium shale sample and did not consider the effect of the vanadium mother liquor in the internal circulation process, thus failing to achieve full-scale utilization of vanadium extraction industrial wastewater.

[0005] Qihua Shi et al. (Qihua Shi, Yimin Zhang, Tao Liu, and Jing Huang. Recycling of Ammonia Wastewater During Vanadium Extraction from Shale, [J]. Journal of Metals, 2018, 70, 1991-1996) investigated the effect of internal recycling of vanadium leaching mother liquor from a vanadium shale (CaO content 4.75 wt%) in Tongshan, Hubei Province, on the vanadium leaching rate. The results showed that the vanadium leaching mother liquor had no effect on vanadium leaching, and the presence of high concentrations of ammonium ions promoted the removal of aluminum from the subsequent leachate. This study, using vanadium shale sulfonated roasted samples as the research object, enhanced the destruction of vanadium-bearing mineral structures through the sulfonation roasting process, while significantly eliminating calcium in the vanadium shale and SO4 in the wastewater. 2- While the process has synergistic negative effects, the sulfation roasting process is complex and difficult to control, and the impact of the raffinate on the entire vanadium extraction process is not considered, thus failing to achieve full utilization of industrial wastewater from vanadium extraction.

[0006] Zhang Guobin (Zhang Guobin. Research on the Recycling of Vanadium Extraction Residue and Vanadium Precipitating Mother Liquor from Vanadium Extraction from Stone Coal [D]. Wuhan University of Science and Technology, 2014) used a low-calcium oxidized vanadium shale (CaO content 0.43 wt%) in Xiushui, Jiangxi Province as the research object. The residue was returned to the vanadium shale leaching and leaching residue washing stages, and the vanadium precipitation mother liquor was adjusted to pH 10 and used as a back-extraction solvent. The impact of wastewater recycling on the entire process, including leaching, extraction, and vanadium product preparation, was investigated. The results showed that the above-mentioned wastewater recycling technology for vanadium extraction does not have a negative impact on the vanadium extraction process from shale. However, this work only studied low-calcium oxidized vanadium shale and did not explore vanadium shale, which is more difficult to process; furthermore, due to the need to adjust the pH of the vanadium precipitation mother liquor, secondary waste residue is generated during wastewater recycling, affecting the acquisition of high-purity by-products.

[0007] The patented technology, "Deep Treatment and Reuse Device and Method for Vanadium Extraction Wastewater from Blank Roasting of Coal Shale and its Application," (CN 109437463 B), involves pretreating vanadium extraction wastewater with a large amount of lime to raise its pH value. The wastewater is then treated through neutralization, precipitation, oxidation, membrane filtration, concentration, and crystallization evaporation. The permeate from the concentration system and the condensate from the evaporation and crystallization system are collected as recycled water and reused in the vanadium extraction production process. While this method effectively treats vanadium extraction wastewater and reuses it in production, the process is complex and lengthy.

[0008] In summary, existing methods for recycling vanadium extraction wastewater have several technical drawbacks, including difficulty in achieving full utilization of the wastewater, the generation of secondary waste residue, complex treatment processes, long process flows, and low purity of by-products. Summary of the Invention

[0009] The present invention aims to overcome the defects of the prior art and provides a method for the full recycling of vanadium extraction wastewater from vanadium shale with a simple processing procedure and short process flow. This method enables the full recycling of vanadium extraction industrial wastewater, does not generate secondary waste residue, and can obtain high-purity by-products.

[0010] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0011] Step 1: Crushing and Grinding

[0012] Vanadium shale is crushed and ground to a particle size of less than 74 μm, accounting for 60–85 wt%, to obtain vanadium shale powder.

[0013] Step 2: Calcium removal from vanadium shale

[0014] The solution is prepared with a liquid-to-solid ratio of 0.8–1.0 m. 3 The vanadium shale powder is mixed with HCl at a concentration of 0.5–2.5 mol / L and stirred at 250–400 r / min for 0.5–1 h at 15–40 °C. Solid-liquid separation is then performed to obtain calcium-removed vanadium shale and calcium-removed solution.

[0015] Step 3: Treatment of vanadium extraction wastewater

[0016] The calcium removal solution is mixed with the fully recycled vanadium extraction wastewater to obtain a mixed solution; then, according to the Ca content in the mixed solution... 2+ and SO4 2- The molar ratio is 0.8 to 1.0:1. Calcium chloride or sodium sulfate is added to the mixture; then, the mixture is stirred at 15 to 40°C for 20 to 60 minutes to separate the solid and liquid, yielding treated vanadium extraction wastewater and high-purity calcium sulfate byproduct.

[0017] The vanadium extraction wastewater is a complete mixture of raffinate and vanadium precipitation mother liquor produced by subsequent processes.

[0018] Step 4: Vanadium Leaching

[0019] According to the mass ratio of calcium-removed vanadium shale to concentrated sulfuric acid of 1:0.25-0.35, concentrated sulfuric acid is added to the calcium-removed vanadium shale to obtain mixed slurry I; then, according to the liquid-solid ratio of 1.0-2.0 m... 3 / t, add the treated vanadium extraction wastewater to the mixed slurry I, mix well, and obtain mixed slurry II.

[0020] According to the mass ratio of calcium-free vanadium shale to calcium fluoride of 1:0.03-0.05, the calcium fluoride is added to the mixed slurry II, and the mixture is stirred at 250-400 r / min for 8-12 h at 90-100℃. Solid-liquid separation is then performed to obtain leachate and leachate residue.

[0021] Step 5: Adjust pH value and reduce

[0022] The pH of the leachate is adjusted to 1.3-1.9 using an alkaline solution, and the solid and liquid are separated to obtain a neutralized leachate and a neutralized residue. Sodium sulfite is added to the neutralized leachate, and the mixture is stirred at 250-400 r / min for 20-30 min at 25-60°C to obtain the original extract.

[0023] The amount of sodium sulfite added is 1.0 to 1.5 times the total amount of sodium sulfite required to reduce pentavalent vanadium and trivalent iron in the neutralized leachate to tetravalent vanadium and divalent iron, respectively.

[0024] Step Six: Forward Extraction and Back Extraction

[0025] The extractant, TBP, and sulfonated kerosene are mixed in a volume ratio of 0.1–0.3:0.02–0.1:1 to obtain an organic phase. The extractant and the organic phase are mixed in a volume ratio of 2–6:1, and subjected to countercurrent extraction for 3–5 stages to obtain a loaded organic phase and raffinate. The loaded organic phase and the back-extraction agent are mixed in a volume ratio of 4–16:1, and subjected to countercurrent back-extraction for 2–5 stages to obtain a vanadium-rich solution and a lean organic phase.

[0026] The temperatures for the countercurrent forward extraction and countercurrent reverse extraction are 20–50°C.

[0027] The single-stage forward extraction time in the countercurrent forward extraction is 5–10 min, and the single-stage back extraction time in the countercurrent reverse extraction is 5–30 min.

[0028] The stripping agent is a sulfuric acid solution with a volume concentration of 8-20 vol%.

[0029] The raffinate is returned to step three.

[0030] Step 7: Vanadium precipitation

[0031] An oxidant is added to the vanadium-rich solution, and the solution is stirred and oxidized at 20–50°C for 0.2–1.0 h to obtain an oxidized vanadium-rich solution. The pH of the oxidized vanadium-rich solution is adjusted to 1.8–2.0 with ammonia water, and the solution is stirred at 250–400 r / min at 80–100°C for 1.0–2.0 h. Solid-liquid separation is performed to obtain ammonium polyvanadate and vanadium precipitate mother liquor.

[0032] The amount of oxidant added is 1.0 to 1.2 times the total amount of oxidant required to oxidize tetravalent vanadium and divalent iron in the vanadium-rich solution to pentavalent vanadium and trivalent iron, respectively.

[0033] The vanadium precipitate mother liquor is returned to step three.

[0034] The vanadium shale has a vanadium content of ≥0.3wt% and a CaO content of ≥4.5wt%.

[0035] The calcium chloride has a Ca content ≥ 35 wt%.

[0036] The concentration of the concentrated sulfuric acid is ≥95wt%.

[0037] The calcium fluoride has an F content of ≥47.5wt%.

[0038] The alkaline solution is one of sodium carbonate solution, sodium hydroxide solution, calcium carbonate solution, calcium hydroxide solution, and calcium oxide solution.

[0039] The oxidant is one of hydrogen peroxide, sodium chlorate, and sodium hypochlorite.

[0040] The extractant is P204 or P507.

[0041] By adopting the above technical solution, the present invention has the following beneficial effects:

[0042] 1. This invention focuses on vanadium shale and, through in-depth research, clarifies the SO4 content in the vanadium extraction industrial wastewater recycling process. 2- Cyclic enrichment inhibits the ionization of sulfuric acid (H+) during leaching. + The degree of calcium depletion in vanadium shale, along with the formation of large amounts of calcium sulfate from calcium (Ca) in the vanadium leaching solution, weakens the vanadium leaching mass transfer efficiency. Based on this mechanism, this invention proposes using hydrochloric acid solution to remove calcium from vanadium shale, and then using the resulting decalcified solution to treat vanadium extraction industrial wastewater, which can significantly reduce SO4 in the circulating wastewater. 2- Concentration, elimination of SO4 2-Negative effects on sulfuric acid ionization and leaching mass transfer. Adopting a "calcium-based treatment" strategy, fully utilizing the calcium resources in vanadium shale to reduce SO4 levels in wastewater. 2- The effective removal of vanadium has enabled the full-scale recycling of vanadium extraction wastewater.

[0043] 2. This invention uses calcium removal solution to treat vanadium extraction wastewater, which will produce calcium sulfate byproduct. Due to the low pH value of the solution and the low impurity content in the solution, the co-precipitation of other impurities is not likely to occur, and the purity of the byproduct is as high as 99% or more, thus avoiding the generation of secondary waste residue.

[0044] 3. This invention uses a calcium removal solution to treat the raffinate and vanadium precipitation mother liquor in a unified and efficient manner. It only requires the use of hydrochloric acid to remove calcium beforehand, and then the calcium removal solution and vanadium extraction wastewater are mixed. This process is simple and has a short production cycle. At the same time, after the vanadium extraction wastewater is recycled, the comprehensive vanadium recovery rate is ≥85% and the purity of the vanadium product is ≥98.5%.

[0045] Therefore, this invention not only achieves full-scale recycling of vanadium extraction wastewater, but also features a simple process, short production cycle, no secondary waste residue, and the ability to obtain high-purity by-products. Detailed Implementation

[0046] The present invention will be further described below with reference to specific embodiments, but this is not intended to limit the scope of protection thereof:

[0047] A method for the complete recycling of vanadium extraction wastewater from vanadium shale. The steps of the method for the complete recycling of vanadium extraction wastewater described in this specific embodiment are as follows:

[0048] Step 1: Crushing and Grinding

[0049] Vanadium shale is crushed and ground to a particle size of less than 74 μm, accounting for 60–85 wt%, to obtain vanadium shale powder.

[0050] Step 2: Calcium removal from vanadium shale

[0051] The solution is prepared with a liquid-to-solid ratio of 0.8–1.0 m. 3 The vanadium shale powder is mixed with HCl at a concentration of 0.5–2.5 mol / L and stirred at 250–400 r / min for 0.5–1 h at 15–40 °C. Solid-liquid separation is then performed to obtain calcium-removed vanadium shale and calcium-removed solution.

[0052] Step 3: Treatment of vanadium extraction wastewater

[0053] The calcium removal solution is mixed with the fully recycled vanadium extraction wastewater to obtain a mixed solution; then, according to the Ca content in the mixed solution... 2+ and SO4 2-The molar ratio is 0.8 to 1.0:1. Calcium chloride or sodium sulfate is added to the mixture; then, the mixture is stirred at 15 to 40°C for 20 to 60 minutes to separate the solid and liquid, yielding treated vanadium extraction wastewater and high-purity calcium sulfate byproduct.

[0054] The vanadium extraction wastewater is a complete mixture of raffinate and vanadium precipitation mother liquor produced by subsequent processes.

[0055] Step 4: Vanadium Leaching

[0056] According to the mass ratio of calcium-removed vanadium shale to concentrated sulfuric acid of 1:0.25-0.35, concentrated sulfuric acid is added to the calcium-removed vanadium shale to obtain mixed slurry I; then, according to the liquid-solid ratio of 1.0-2.0 m... 3 / t, add the treated vanadium extraction wastewater to the mixed slurry I, mix well, and obtain mixed slurry II.

[0057] According to the mass ratio of calcium-free vanadium shale to calcium fluoride of 1:0.03-0.05, the calcium fluoride is added to the mixed slurry II, and the mixture is stirred at 250-400 r / min for 8-12 h at 90-100℃. Solid-liquid separation is then performed to obtain leachate and leachate residue.

[0058] Step 5: Adjust pH value and reduce

[0059] The pH of the leachate is adjusted to 1.3-1.9 using an alkaline solution, and the solid and liquid are separated to obtain a neutralized leachate and a neutralized residue. Sodium sulfite is added to the neutralized leachate, and the mixture is stirred at 250-400 r / min for 20-30 min at 25-60°C to obtain the original extract.

[0060] The amount of sodium sulfite added is 1.0 to 1.5 times the total amount of sodium sulfite required to reduce pentavalent vanadium and trivalent iron in the neutralized leachate to tetravalent vanadium and divalent iron, respectively.

[0061] Step Six: Forward Extraction and Back Extraction

[0062] The extractant, TBP, and sulfonated kerosene are mixed in a volume ratio of 0.1–0.3:0.02–0.1:1 to obtain an organic phase. The extractant and the organic phase are mixed in a volume ratio of 2–6:1, and subjected to countercurrent extraction for 3–5 stages to obtain a loaded organic phase and raffinate. The loaded organic phase and the back-extraction agent are mixed in a volume ratio of 4–16:1, and subjected to countercurrent back-extraction for 2–5 stages to obtain a vanadium-rich solution and a lean organic phase.

[0063] The temperatures for the countercurrent forward extraction and countercurrent reverse extraction are 20–50°C.

[0064] The single-stage forward extraction time in the countercurrent forward extraction is 5–10 min, and the single-stage back extraction time in the countercurrent reverse extraction is 5–30 min.

[0065] The stripping agent is a sulfuric acid solution with a volume concentration of 8-20 vol%.

[0066] The raffinate is returned to step three.

[0067] Step 7: Vanadium precipitation

[0068] An oxidant is added to the vanadium-rich solution, and the solution is stirred and oxidized at 20–50°C for 0.2–1.0 h to obtain an oxidized vanadium-rich solution. The pH of the oxidized vanadium-rich solution is adjusted to 1.8–2.0 with ammonia water, and the solution is stirred at 250–400 r / min at 80–100°C for 1.0–2.0 h. Solid-liquid separation is performed to obtain ammonium polyvanadate and vanadium precipitate mother liquor.

[0069] The amount of oxidant added is 1.0 to 1.2 times the total amount of oxidant required to oxidize tetravalent vanadium and divalent iron in the vanadium-rich solution to pentavalent vanadium and trivalent iron, respectively.

[0070] The vanadium precipitate mother liquor is returned to step three.

[0071] The vanadium shale has a vanadium content of ≥0.3wt% and a CaO content of ≥4.5wt%.

[0072] The calcium chloride has a Ca content ≥ 35 wt%.

[0073] The concentration of the concentrated sulfuric acid is ≥95wt%.

[0074] The calcium fluoride has an F content of ≥47.5wt%.

[0075] The alkaline solution is one of sodium carbonate solution, sodium hydroxide solution, calcium carbonate solution, calcium hydroxide solution, and calcium oxide solution.

[0076] The oxidant is one of hydrogen peroxide, sodium chlorate, and sodium hypochlorite.

[0077] The extractant is P204 or P507.

[0078] Example 1

[0079] A method for the complete recycling of vanadium extraction wastewater from vanadium shale. The steps of the method for the complete recycling of vanadium extraction wastewater described in this embodiment are as follows:

[0080] Step 1: Crushing and Grinding

[0081] Vanadium shale is crushed and ground to a particle size of less than 74 μm, accounting for 70 wt%, to obtain vanadium shale powder.

[0082] Step 2: Calcium removal from vanadium shale

[0083] The solution is prepared with a liquid-to-solid ratio of 0.9m. 3 The vanadium shale powder was mixed with 0.5 mol / L HCl and stirred at 250 r / min for 0.75 h at 15 °C. After solid-liquid separation, calcium-removed vanadium shale and calcium-removed solution were obtained.

[0084] Step 3: Treatment of vanadium extraction wastewater

[0085] The calcium removal solution is mixed with the fully recycled vanadium extraction wastewater to obtain a mixed solution; then, according to the Ca content in the mixed solution... 2+ and SO4 2- The molar ratio is 0.92:1. Calcium chloride or sodium sulfate is added to the mixture, and then the mixture is stirred at 23°C for 25 minutes. Solid-liquid separation is performed to obtain treated vanadium extraction wastewater and high-purity calcium sulfate byproduct.

[0086] The vanadium extraction wastewater is a complete mixture of raffinate and vanadium precipitation mother liquor produced by subsequent processes.

[0087] Step 4: Vanadium Leaching

[0088] According to the mass ratio of calcium-removed vanadium shale to concentrated sulfuric acid of 1:0.275, concentrated sulfuric acid was added to the calcium-removed vanadium shale to obtain mixed slurry I; then, according to the liquid-to-solid ratio of 2.0 m... 3 / t, add the treated vanadium extraction wastewater to the mixed slurry I, mix well, and obtain mixed slurry II.

[0089] According to the mass ratio of calcium-free vanadium shale to calcium fluoride of 1:0.035, the calcium fluoride was added to the mixed slurry II, and the mixture was stirred at 275 r / min for 8 h at 98 °C. Solid-liquid separation was then performed to obtain leachate and leachate residue.

[0090] Step 5: Adjust pH value and reduce

[0091] The pH of the leachate was adjusted to 1.9 with an alkaline solution, and the solid and liquid were separated to obtain a neutralized leachate and a neutralized residue. Sodium sulfite was added to the neutralized leachate, and the mixture was stirred at 295 r / min for 20 min at 30°C to obtain the original extract.

[0092] The amount of sodium sulfite added is 1.25 times the total amount of sodium sulfite required to reduce pentavalent vanadium and trivalent iron in the neutralized leachate to tetravalent vanadium and divalent iron, respectively.

[0093] Step Six: Forward Extraction and Back Extraction

[0094] The extractant, TBP, and sulfonated kerosene were mixed at a volume ratio of 0.25:0.05:1 to obtain an organic phase. The extractant, TBP, and sulfonated kerosene were then mixed at a volume ratio of 4:1 to obtain a loaded organic phase and raffinate. Finally, the loaded organic phase and the back-extraction agent were mixed at a volume ratio of 5:1 to obtain a vanadium-rich solution and a lean organic phase.

[0095] The temperature for both the countercurrent forward extraction and the countercurrent reverse extraction is 20°C.

[0096] The single-stage forward extraction time in the countercurrent forward extraction is 9 minutes, and the single-stage back extraction time in the countercurrent reverse extraction is 18 minutes.

[0097] The stripping agent is a sulfuric acid solution with a volume concentration of 12 vol%.

[0098] The raffinate is returned to step three.

[0099] Step 7: Vanadium precipitation

[0100] An oxidant was added to the vanadium-rich solution, and the solution was stirred and oxidized at 20°C for 0.6 h to obtain an oxidized vanadium-rich solution. The pH of the oxidized vanadium-rich solution was adjusted to 1.87 with ammonia water, and the solution was stirred at 400 r / min at 98°C for 1.8 h. Solid-liquid separation was performed to obtain ammonium polyvanadate and vanadium precipitate mother liquor.

[0101] The amount of oxidant added is 1.0 times the total amount of oxidant required to oxidize tetravalent vanadium and divalent iron in the vanadium-rich solution to pentavalent vanadium and trivalent iron, respectively.

[0102] The vanadium precipitate mother liquor is returned to step three.

[0103] The vanadium shale has a vanadium content of 0.4 wt% and a CaO content of 5.24 wt%.

[0104] The calcium chloride has a Ca content of 35.15 wt%.

[0105] The concentration of the concentrated sulfuric acid is 95 wt%.

[0106] The calcium fluoride has an F content of 47.5 wt%.

[0107] The alkaline solution is a sodium carbonate solution.

[0108] The oxidant is hydrogen peroxide.

[0109] The extractant is P2O4.

[0110] The following tests were conducted in this embodiment: vanadium leaching rate was 87.58%; extraction rate was 99.16%; back-extraction rate was 99.63%; vanadium precipitation rate was 99.48%; vanadium product purity was 98.663%; and by-product purity was 99.278%.

[0111] Example 2

[0112] A method for the complete recycling of vanadium extraction wastewater from vanadium shale. The steps of the method for the complete recycling of vanadium extraction wastewater described in this embodiment are as follows:

[0113] Step 1: Crushing and Grinding

[0114] Vanadium shale is crushed and ground to a particle size of less than 74 μm, accounting for 65 wt%, to obtain vanadium shale powder.

[0115] Step 2: Calcium removal from vanadium shale

[0116] The solution is prepared with a liquid-to-solid ratio of 1.0 m. 3 The vanadium shale powder was mixed with 0.9 mol / L HCl and stirred at 280 r / min for 1 h at 28 °C. After solid-liquid separation, calcium-removed vanadium shale and calcium-removed solution were obtained.

[0117] Step 3: Treatment of vanadium extraction wastewater

[0118] The calcium removal solution is mixed with the fully recycled vanadium extraction wastewater to obtain a mixed solution; then, according to the Ca content in the mixed solution... 2+ and SO4 2- The molar ratio is 0.8:1. Calcium chloride or sodium sulfate is added to the mixture, and then the mixture is stirred at 28°C for 60 minutes. Solid-liquid separation is performed to obtain treated vanadium extraction wastewater and high-purity calcium sulfate byproduct.

[0119] The vanadium extraction wastewater is a complete mixture of raffinate and vanadium precipitation mother liquor produced by subsequent processes.

[0120] Step 4: Vanadium Leaching

[0121] According to the mass ratio of calcium-removed vanadium shale to concentrated sulfuric acid of 1:0.25, concentrated sulfuric acid was added to the calcium-removed vanadium shale to obtain mixed slurry I; then, according to the liquid-to-solid ratio of 1.5m... 3 / t, add the treated vanadium extraction wastewater to the mixed slurry I, mix well, and obtain mixed slurry II.

[0122] According to the mass ratio of calcium-free vanadium shale to calcium fluoride of 1:0.038, the calcium fluoride was added to the mixed slurry II, and the mixture was stirred at 310 r / min for 11 h at 95 °C. Solid-liquid separation was then performed to obtain leachate and leachate residue.

[0123] Step 5: Adjust pH value and reduce

[0124] The pH of the leachate was adjusted to 1.68 with an alkaline solution, and the solid and liquid were separated to obtain a neutralized leachate and a neutralized residue. Sodium sulfite was added to the neutralized leachate, and the mixture was stirred at 400 r / min for 26 min at 45°C to obtain the original extract.

[0125] The amount of sodium sulfite added is 1.4 times the total amount of sodium sulfite required to reduce pentavalent vanadium and trivalent iron in the neutralized leachate to tetravalent vanadium and divalent iron, respectively.

[0126] Step Six: Forward Extraction and Back Extraction

[0127] The extractant, TBP, and sulfonated kerosene were mixed at a volume ratio of 0.3:0.07:1 to obtain an organic phase. The extractant, TBP, and sulfonated kerosene were then mixed at a volume ratio of 2:1 to obtain a loaded organic phase and raffinate. Finally, the loaded organic phase and the back-extraction agent were mixed at a volume ratio of 8:1 to obtain a vanadium-rich solution and a lean organic phase.

[0128] The temperature for both the countercurrent forward extraction and the countercurrent reverse extraction is 30°C.

[0129] The single-stage forward extraction time in the countercurrent forward extraction is 7 minutes, and the single-stage back extraction time in the countercurrent reverse extraction is 22 minutes.

[0130] The stripping agent is a sulfuric acid solution with a volume concentration of 10 vol%.

[0131] The raffinate is returned to step three.

[0132] Step 7: Vanadium precipitation

[0133] An oxidant was added to the vanadium-rich solution, and the solution was stirred and oxidized at 30°C for 0.5 h to obtain an oxidized vanadium-rich solution. The pH of the oxidized vanadium-rich solution was adjusted to 1.91 with ammonia water, and the solution was stirred at 310 r / min at 88°C for 1 h to separate ammonium polyvanadate and vanadium precipitate mother liquor.

[0134] The amount of oxidant added is 1.05 times the total amount of oxidant required to oxidize tetravalent vanadium and divalent iron in the vanadium-rich solution to pentavalent vanadium and trivalent iron, respectively.

[0135] The vanadium precipitate mother liquor is returned to step three.

[0136] The vanadium shale has a vanadium content of 0.3 wt% and a CaO content of 5.97 wt%.

[0137] The calcium chloride has a Ca content of 35.36 wt%.

[0138] The concentration of the concentrated sulfuric acid is 96.15 wt%.

[0139] The calcium fluoride has an F content of 47.8 wt%.

[0140] The alkaline solution is a sodium hydroxide solution.

[0141] The oxidant is sodium chlorate.

[0142] The extractant is P507.

[0143] The following tests were conducted in this embodiment: vanadium leaching rate was 85.54%; extraction rate was 99.54%; back-extraction rate was 99.01%; vanadium precipitation rate was 98.17%; vanadium product purity was 98.938%; and by-product purity was 99.611%.

[0144] Example 3

[0145] A method for the complete recycling of vanadium extraction wastewater from vanadium shale. The steps of the method for the complete recycling of vanadium extraction wastewater described in this embodiment are as follows:

[0146] Step 1: Crushing and Grinding

[0147] Vanadium shale is crushed and ground to a particle size of less than 74 μm, accounting for 60 wt%, to obtain vanadium shale powder.

[0148] Step 2: Calcium removal from vanadium shale

[0149] The solution is prepared with a liquid-to-solid ratio of 0.95m. 3 The vanadium shale powder was mixed with HCl at a concentration of 2.5 mol / L and stirred at 320 r / min for 0.8 h at 40 °C. After solid-liquid separation, calcium-removed vanadium shale and calcium-removed solution were obtained.

[0150] Step 3: Treatment of vanadium extraction wastewater

[0151] The calcium removal solution is mixed with the fully recycled vanadium extraction wastewater to obtain a mixed solution; then, according to the Ca content in the mixed solution... 2+ and SO4 2- The molar ratio is 1:1. Calcium chloride or sodium sulfate is added to the mixture, and then the mixture is stirred at 40°C for 38 minutes. Solid-liquid separation is performed to obtain treated vanadium extraction wastewater and high-purity calcium sulfate byproduct.

[0152] The vanadium extraction wastewater is a complete mixture of raffinate and vanadium precipitation mother liquor produced by subsequent processes.

[0153] Step 4: Vanadium Leaching

[0154] According to the mass ratio of calcium-removed vanadium shale to concentrated sulfuric acid of 1:0.35, concentrated sulfuric acid was added to the calcium-removed vanadium shale to obtain mixed slurry I; then, according to the liquid-to-solid ratio of 1.9m...3 / t, add the treated vanadium extraction wastewater to the mixed slurry I, mix well, and obtain mixed slurry II.

[0155] According to the mass ratio of calcium-free vanadium shale to calcium fluoride of 1:0.05, the calcium fluoride was added to the mixed slurry II, and the mixture was stirred at 380 r / min for 12 h at 100 °C. Solid-liquid separation was then performed to obtain leachate and leachate residue.

[0156] Step 5: Adjust pH value and reduce

[0157] The pH of the leachate was adjusted to 1.75 with an alkaline solution, and the solid and liquid were separated to obtain a neutralized leachate and a neutralized residue. Sodium sulfite was added to the neutralized leachate, and the mixture was stirred at 250 r / min for 30 min at 60°C to obtain the original extract.

[0158] The amount of sodium sulfite added is 1.0 times the total amount of sodium sulfite required to reduce pentavalent vanadium and trivalent iron in the neutralized leachate to tetravalent vanadium and divalent iron, respectively.

[0159] Step Six: Forward Extraction and Back Extraction

[0160] The extractant, TBP, and sulfonated kerosene were mixed at a volume ratio of 0.18:0.045:1 to obtain an organic phase. The extractant and the organic phase were then mixed at a volume ratio of 3:1 and subjected to four countercurrent extraction stages to obtain a loaded organic phase and raffinate. Finally, the loaded organic phase and the back-extraction agent were mixed at a volume ratio of 10:1 and subjected to four countercurrent back-extraction stages to obtain a vanadium-rich solution and a lean organic phase.

[0161] The temperature for both the countercurrent forward extraction and the countercurrent reverse extraction is 45°C.

[0162] The single-stage forward extraction time in the countercurrent forward extraction is 8 minutes, and the single-stage back extraction time in the countercurrent reverse extraction is 30 minutes.

[0163] The stripping agent is a sulfuric acid solution with a volume concentration of 15 vol%.

[0164] The raffinate is returned to step three.

[0165] Step 7: Vanadium precipitation

[0166] An oxidant was added to the vanadium-rich solution, and the solution was stirred and oxidized at 45°C for 0.8 h to obtain an oxidized vanadium-rich solution. The pH of the oxidized vanadium-rich solution was adjusted to 1.80 with ammonia water, and the solution was stirred at 380 r / min at 100°C for 1.5 h to separate ammonium polyvanadate and vanadium precipitate mother liquor.

[0167] The amount of oxidant added is 1.2 times the total amount of oxidant required to oxidize tetravalent vanadium and divalent iron in the vanadium-rich solution to pentavalent vanadium and trivalent iron, respectively.

[0168] The vanadium precipitate mother liquor is returned to step three.

[0169] The vanadium shale has a vanadium content of 0.392 wt% and a CaO content of 7.12 wt%.

[0170] The calcium chloride has a Ca content of 35.74 wt%.

[0171] The concentration of the concentrated sulfuric acid is 96.05 wt%.

[0172] The calcium fluoride has an F content of 48.23 wt%.

[0173] The alkaline solution is a calcium hydroxide solution.

[0174] The oxidant is sodium hypochlorite.

[0175] The extractant used was P204. In this embodiment, the following results were obtained: vanadium leaching rate was 88.59%; extraction rate was 99.27%; back-extraction rate was 99.77%; vanadium precipitation rate was 99.36%; vanadium product purity was 98.576%; and by-product purity was 99.491%.

[0176] Example 4

[0177] A method for the complete recycling of vanadium extraction wastewater from vanadium shale. The steps of the method for the complete recycling of vanadium extraction wastewater described in this embodiment are as follows:

[0178] Step 1: Crushing and Grinding

[0179] Vanadium shale was crushed and ground to a particle size of less than 74 μm, accounting for 79 wt.%, to obtain vanadium shale powder.

[0180] Step 2: Calcium removal from vanadium shale

[0181] The solution is prepared with a liquid-to-solid ratio of 0.9m. 3 The vanadium shale powder was mixed with HCl at a concentration of 1.85 mol / L and stirred at 400 r / min for 1 h at 35 °C. After solid-liquid separation, calcium-removed vanadium shale and calcium-removed solution were obtained.

[0182] Step 3: Treatment of vanadium extraction wastewater

[0183] The calcium removal solution is mixed with the fully recycled vanadium extraction wastewater to obtain a mixed solution; then, according to the Ca content in the mixed solution... 2+ and SO4 2-The molar ratio is 0.95:1. Calcium chloride or sodium sulfate is added to the mixture, and then the mixture is stirred at 35°C for 49 minutes. Solid-liquid separation is performed to obtain treated vanadium extraction wastewater and high-purity calcium sulfate byproduct.

[0184] The vanadium extraction wastewater is a complete mixture of raffinate and vanadium precipitation mother liquor produced by subsequent processes.

[0185] Step 4: Vanadium Leaching

[0186] According to the mass ratio of calcium-removed vanadium shale to concentrated sulfuric acid of 1:0.30, concentrated sulfuric acid was added to the calcium-removed vanadium shale to obtain mixed slurry I; then, according to the liquid-to-solid ratio of 1.7m... 3 / t, add the treated vanadium extraction wastewater to the mixed slurry I, mix well, and obtain mixed slurry II.

[0187] According to the mass ratio of calcium-free vanadium shale to calcium fluoride of 1:0.045, the calcium fluoride was added to the mixed slurry II, and the mixture was stirred at 350 r / min for 9.5 h at 95 °C. Solid-liquid separation was then performed to obtain leachate and leachate residue.

[0188] Step 5: Adjust pH value and reduce

[0189] The pH of the leachate was adjusted to 1.30 with an alkaline solution, and the solid and liquid were separated to obtain a neutralized leachate and a neutralized residue. Sodium sulfite was added to the neutralized leachate, and the mixture was stirred at 295 r / min for 25 min at 48°C to obtain the original extract.

[0190] The amount of sodium sulfite added is 1.35 times the total amount of sodium sulfite required to reduce pentavalent vanadium and trivalent iron in the neutralized leachate to tetravalent vanadium and divalent iron, respectively.

[0191] Step Six: Forward Extraction and Back Extraction

[0192] The extractant, TBP, and sulfonated kerosene were mixed at a volume ratio of 0.2:0.09:1 to obtain an organic phase. The extractant, TBP, and sulfonated kerosene were then mixed at a volume ratio of 5:1 to obtain a loaded organic phase and raffinate. Finally, the loaded organic phase and the back-extraction agent were mixed at a volume ratio of 12:1 to obtain a vanadium-rich solution and a lean organic phase.

[0193] The temperature for both the countercurrent forward extraction and the countercurrent reverse extraction is 40°C.

[0194] The single-stage forward extraction time in the countercurrent forward extraction is 5 min, and the single-stage back extraction time in the countercurrent reverse extraction is 26 min.

[0195] The stripping agent is a sulfuric acid solution with a volume concentration of 8 vol%.

[0196] The raffinate is returned to step three.

[0197] Step 7: Vanadium precipitation

[0198] An oxidant was added to the vanadium-rich solution, and the solution was stirred and oxidized at 40°C for 1 hour to obtain an oxidized vanadium-rich solution. The pH of the oxidized vanadium-rich solution was adjusted to 1.95 with ammonia water, and the solution was stirred at 350 r / min at 95°C for 2 hours to separate ammonium polyvanadate and vanadium precipitate mother liquor.

[0199] The amount of oxidant added is 1.15 times the total amount of oxidant required to oxidize tetravalent vanadium and divalent iron in the vanadium-rich solution to pentavalent vanadium and trivalent iron, respectively.

[0200] The vanadium precipitate mother liquor is returned to step three.

[0201] The vanadium shale has a vanadium content of 0.51 wt% and a CaO content of 6.44 wt%.

[0202] The calcium chloride has a Ca content of 35.58 wt%.

[0203] The concentration of the concentrated sulfuric acid was 97.02 wt%.

[0204] The calcium fluoride has an F content of 47.98 wt%.

[0205] The alkaline solution is a calcium carbonate solution.

[0206] The oxidant is sodium chlorate.

[0207] The extractant used was P507. In this embodiment, the following results were obtained: vanadium leaching rate was 87.26%; extraction rate was 99.14%; back-extraction rate was 99.34%; vanadium precipitation rate was 98.83%; vanadium product purity was 98.797%; and by-product purity was 99.289%.

[0208] Example 5

[0209] A method for the complete recycling of vanadium extraction wastewater from vanadium shale. The steps of the method for the complete recycling of vanadium extraction wastewater described in this embodiment are as follows:

[0210] Step 1: Crushing and Grinding

[0211] Vanadium shale is crushed and ground to a particle size of less than 74 μm, accounting for 84 wt%, to obtain vanadium shale powder.

[0212] Step 2: Calcium removal from vanadium shale

[0213] The solution is prepared with a liquid-to-solid ratio of 0.8m. 3The vanadium shale powder was mixed with HCl at a concentration of 1.4 mol / L and stirred at 370 r / min for 0.6 h at 25 °C. After solid-liquid separation, calcium-removed vanadium shale and calcium-removed solution were obtained.

[0214] Step 3: Treatment of vanadium extraction wastewater

[0215] The calcium removal solution is mixed with the fully recycled vanadium extraction wastewater to obtain a mixed solution; then, according to the Ca content in the mixed solution... 2+ and SO4 2- The molar ratio is 0.85:1. Calcium chloride or sodium sulfate is added to the mixture, and then the mixture is stirred at 25°C for 52 minutes. Solid-liquid separation is performed to obtain vanadium extraction wastewater and high-purity calcium sulfate byproduct after treatment.

[0216] The vanadium extraction wastewater is a complete mixture of raffinate and vanadium precipitation mother liquor produced by subsequent processes.

[0217] Step 4: Vanadium Leaching

[0218] According to the mass ratio of calcium-removed vanadium shale to concentrated sulfuric acid of 1:0.32, concentrated sulfuric acid was added to the calcium-removed vanadium shale to obtain mixed slurry I; then, according to the liquid-to-solid ratio of 1.3m... 3 / t, add the treated vanadium extraction wastewater to the mixed slurry I, mix well, and obtain mixed slurry II.

[0219] According to the mass ratio of calcium-free vanadium shale to calcium fluoride of 1:0.042, the calcium fluoride was added to the mixed slurry II, and the mixture was stirred at 400 r / min for 10 h at 97 °C. Solid-liquid separation was then performed to obtain leachate and leachate residue.

[0220] Step 5: Adjust pH value and reduce

[0221] The pH of the leachate was adjusted to 1.56 with an alkaline solution, and the solid and liquid were separated to obtain a neutralized leachate and a neutralized residue. Sodium sulfite was added to the neutralized leachate, and the mixture was stirred at 345 r / min for 29 min at 25°C to obtain the original extract.

[0222] The amount of sodium sulfite added is 1.5 times the total amount of sodium sulfite required to reduce pentavalent vanadium and trivalent iron in the neutralized leachate to tetravalent vanadium and divalent iron, respectively.

[0223] Step Six: Forward Extraction and Back Extraction

[0224] The extractant, TBP, and sulfonated kerosene were mixed at a volume ratio of 0.1:0.06:1 to obtain an organic phase. The extractant, TBP, and sulfonated kerosene were then mixed at a volume ratio of 6:1 to obtain an organic phase. The mixture was subjected to four countercurrent extraction stages to obtain a loaded organic phase and raffinate. Finally, the loaded organic phase and the back-extraction agent were mixed at a volume ratio of 16:1 to obtain a vanadium-rich solution and a lean organic phase.

[0225] The temperature for both the countercurrent forward extraction and the countercurrent reverse extraction is 50°C.

[0226] The single-stage forward extraction time in the countercurrent forward extraction is 10 min, and the single-stage back extraction time in the countercurrent reverse extraction is 5 min.

[0227] The stripping agent is a sulfuric acid solution with a volume concentration of 20 vol%.

[0228] The raffinate is returned to step three.

[0229] Step 7: Vanadium precipitation

[0230] An oxidant was added to the vanadium-rich solution, and the solution was stirred and oxidized at 50°C for 0.2 h to obtain an oxidized vanadium-rich solution. The pH of the oxidized vanadium-rich solution was adjusted to 2.0 with ammonia water, and the solution was stirred at 80°C and 250 r / min for 1.25 h to separate ammonium polyvanadate and vanadium precipitate mother liquor.

[0231] The amount of oxidant added is 1.1 times the total amount of oxidant required to oxidize tetravalent vanadium and divalent iron in the vanadium-rich solution to pentavalent vanadium and trivalent iron, respectively.

[0232] The vanadium precipitate mother liquor is returned to step three.

[0233] The vanadium shale has a vanadium content of 0.63 wt% and a CaO content of 4.5 wt%.

[0234] The calcium chloride has a Ca content of 35.36 wt%.

[0235] The concentration of the concentrated sulfuric acid was 96.35 wt%.

[0236] The calcium fluoride has an F content of 48.23 wt%.

[0237] The alkaline solution is a calcium oxide solution.

[0238] The oxidant is sodium hypochlorite.

[0239] The extractant used was P507. In this embodiment, the following results were obtained: vanadium leaching rate was 86.73%; extraction rate was 99.18%; back-extraction rate was 99.52%; vanadium precipitation rate was 98.65%; vanadium product purity was 98.677%; and by-product purity was 99.341%.

[0240] Compared with the prior art, this specific implementation method has the following positive effects:

[0241] 1. This specific implementation method focuses on vanadium shale. Through in-depth research, it has been clarified that SO4 in the vanadium extraction industrial wastewater recycling process... 2- Cyclic enrichment inhibits the ionization of sulfuric acid (H+) during leaching. + The degree of calcium desulfate formation, along with the calcium in the vanadium shale, produces a large amount of calcium sulfate, weakening the vanadium leaching mass transfer efficiency. Based on this mechanism, this specific embodiment proposes using hydrochloric acid solution to remove calcium from the vanadium shale, and then using the resulting decalcified solution to treat vanadium extraction industrial wastewater, which can significantly reduce the SO4 content in the circulating wastewater. 2- Concentration, elimination of SO4 2- Negative effects on sulfuric acid ionization and leaching mass transfer. Adopting a "calcium-based treatment" strategy, fully utilizing the calcium resources in vanadium shale to reduce SO4 levels in wastewater. 2- The effective removal of vanadium has enabled the full-scale recycling of vanadium extraction wastewater.

[0242] 2. In this specific embodiment, calcium removal solution is used to treat vanadium extraction wastewater, which will produce calcium sulfate byproduct. Due to the low pH value of the solution and the low impurity content in the solution, the co-precipitation of other impurities is not likely to occur, and the purity of the byproduct is as high as 99% or more, thus avoiding the generation of secondary waste residue.

[0243] 3. This specific implementation method uses calcium removal solution to treat the raffinate and vanadium precipitation mother liquor in a unified and efficient manner. It only requires the use of hydrochloric acid to remove calcium in advance, and then the calcium removal solution and vanadium extraction wastewater are mixed. This process is simple and has a short production cycle. At the same time, after the vanadium extraction wastewater is recycled, the comprehensive vanadium recovery rate is ≥85% and the purity of the vanadium product is ≥98.5%.

[0244] Therefore, this specific implementation method not only achieves full-scale recycling of vanadium extraction wastewater, but also features a simple process, short production cycle, no secondary waste residue, and the ability to obtain high-purity by-products.

Claims

1. A method for the complete recycling of vanadium extraction wastewater from vanadium shale, characterized in that... The steps of the method are as follows: Step 1: Crushing and Grinding Vanadium shale is crushed and ground to a particle size of less than 74μm, accounting for 60-85wt%, to obtain vanadium shale powder. Step 2: Calcium removal from vanadium shale The solution is prepared with a liquid-to-solid ratio of 0.8–1.0 m. 3 / t, the vanadium shale powder is mixed with HCl at a concentration of 0.5-2.5 mol / L, and stirred at a speed of 250-400 r / min for 0.5-1 h at 15-40℃, and the solid and liquid are separated to obtain calcium-removed vanadium shale and calcium-removed solution; Step 3: Treatment of vanadium extraction wastewater The calcium removal solution is mixed with the fully recycled vanadium extraction wastewater to obtain a mixed solution; then, according to the Ca content in the mixed solution... 2+ and SO4 2- The molar ratio is 0.8 to 1.0:

1. Calcium chloride or sodium sulfate is added to the mixture; then, the mixture is stirred at 15 to 40°C for 20 to 60 minutes to separate the solid and liquid, yielding treated vanadium extraction wastewater and high-purity calcium sulfate byproduct. The vanadium extraction wastewater is a complete mixture of raffinate and vanadium precipitation mother liquor produced by subsequent processes. Step 4: Vanadium Leaching According to the mass ratio of calcium-removed vanadium shale to concentrated sulfuric acid of 1:0.25-0.35, concentrated sulfuric acid is added to the calcium-removed vanadium shale to obtain mixed slurry I; then, according to the liquid-solid ratio of 1.0-2.0 m... 3 / t, add the treated vanadium extraction wastewater to the mixed slurry I, mix well, and obtain mixed slurry II; According to the mass ratio of calcium-free vanadium shale to calcium fluoride of 1:0.03-0.05, the calcium fluoride is added to the mixed slurry II, and the mixture is stirred at 250-400 r / min for 8-12 h at 90-100℃. Solid-liquid separation is performed to obtain leachate and leachate residue. Step 5: Adjust pH value and reduce The pH of the leachate is adjusted to 1.3-1.9 using an alkaline solution, and the solid and liquid are separated to obtain a neutralized leachate and a neutralized residue. Sodium sulfite is added to the neutralized leachate, and the mixture is stirred at 250-400 r / min for 20-30 min at 25-60°C to obtain the original extract. The amount of sodium sulfite added is 1.0 to 1.5 times the total amount of sodium sulfite required to reduce pentavalent vanadium and trivalent iron in the neutralized leachate to tetravalent vanadium and divalent iron, respectively. Step Six: Forward Extraction and Back Extraction The extractant, TBP, and sulfonated kerosene are mixed in a volume ratio of 0.1–0.3:0.02–0.1:1 to obtain an organic phase. The extractant and the organic phase are mixed in a volume ratio of 2–6:1 and subjected to countercurrent extraction for 3–5 stages to obtain a loaded organic phase and raffinate. The loaded organic phase and the back-extraction agent are mixed in a volume ratio of 4–16:1 and subjected to countercurrent back-extraction for 2–5 stages to obtain a vanadium-rich solution and a lean organic phase. The temperatures for the countercurrent forward extraction and countercurrent reverse extraction are 20–50°C. The single-stage forward extraction time in the countercurrent forward extraction is 5-10 min, and the single-stage back extraction time in the countercurrent reverse extraction is 5-30 min; The stripping agent is a sulfuric acid solution with a volume concentration of 8-20 vol%. The raffinate is returned to step three; Step 7: Vanadium precipitation An oxidant is added to the vanadium-rich solution, and the solution is stirred and oxidized at 20–50°C for 0.2–1.0 h to obtain an oxidized vanadium-rich solution. The pH of the oxidized vanadium-rich solution is adjusted to 1.8–2.0 with ammonia water, and the solution is stirred at 250–400 r / min at 80–100°C for 1.0–2.0 h. Solid-liquid separation is performed to obtain ammonium polyvanadate and vanadium precipitate mother liquor. The amount of oxidant added is 1.0 to 1.2 times the total amount of oxidant required to oxidize tetravalent vanadium and divalent iron in the vanadium-rich solution to pentavalent vanadium and trivalent iron, respectively. The vanadium precipitate mother liquor is returned to step three.

2. The method for full recycling of vanadium extraction wastewater from vanadium shale according to claim 1, characterized in that... The vanadium shale has a vanadium content of ≥0.3wt% and a CaO content of ≥4.5wt%.

3. The method for full recycling of vanadium extraction wastewater from vanadium shale according to claim 1, characterized in that... The calcium chloride has a Ca content ≥ 35 wt%.

4. The method for full recycling of vanadium extraction wastewater from vanadium shale according to claim 1, characterized in that... The concentration of the concentrated sulfuric acid is ≥95wt%.

5. The method for full recycling of vanadium extraction wastewater from vanadium shale according to claim 1, characterized in that... The calcium fluoride has an F content of ≥47.5wt%.

6. The method for full recycling of vanadium extraction wastewater from vanadium shale according to claim 1, characterized in that... The alkaline solution is one of sodium carbonate solution, sodium hydroxide solution, calcium carbonate solution, calcium hydroxide solution, and calcium oxide solution.

7. The method for full recycling of vanadium extraction wastewater from vanadium shale according to claim 1, characterized in that... The oxidant is one of hydrogen peroxide, sodium chlorate, and sodium hypochlorite.

8. The method for full recycling of vanadium extraction wastewater from vanadium shale according to claim 1, characterized in that... The extractant is P204 or P507.