Method for preparing low-chromium low-potassium vanadium oxide from sodium vanadium oxide liquid

Abstract

The invention provides a method for preparing low-chromium low-potassium vanadium oxide by using a sodium vanadium solution, which comprises the following steps: S1) adjusting the pH value of the sodium vanadium solution to 10.5-11.0, and reacting with a chromium removal agent to obtain initial chromium removal slurry; s2) adjusting the pH value of the initial chromium removal slurry to 9.0-9.5, reacting with a silicon removal agent, and carrying out solid-liquid separation to obtain a filtrate; s3) reacting the filtrate with hydrogen peroxide, adding ammonium salt, precipitating vanadium, and performing solid-liquid separation to obtain ammonium metavanadate and primary vanadium precipitation wastewater; s4) adjusting the pH value of the primary vanadium precipitation wastewater to 6-7, reacting with ferrous sulfate, adding a complexing agent, mixing with the sodium vanadium solution, precipitating, and performing solid-liquid separation to obtain ammonium polyvanadate; and oxidizing and calcining the ammonium metavanadate to obtain the low-chromium low-potassium vanadium oxide. According to the method provided by the invention, the low-chromium and low-potassium vanadium oxide is prepared from the sodium vanadium solution, meanwhile, ammonium salt and vanadium in the primary vanadium precipitation wastewater are recycled, and the comprehensive production cost of the vanadium oxide is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of vanadium extraction and metallurgy, and in particular to a method for preparing low-chromium and low-potassium vanadium oxide by utilizing sodium vanadium liquid. Background Art

[0002] "Sodium calcination of vanadium slag - water leaching - acidic ammonium salt vanadium precipitation - wastewater treatment" is the traditional process for producing vanadium oxide from vanadium slag, and it is also the mainstream process for vanadium oxide production at home and abroad. Among the above processes, acidic ammonium salt vanadium precipitation has the advantages of high vanadium precipitation rate and low ammonium salt dosage. Therefore, this process is widely used. During the vanadium slag roasting process, part of the chromium and potassium are converted into water-soluble products and enter the leaching solution, and enter the vanadium product during the vanadium precipitation process. For vanadium oxide with high chromium and potassium content, it can be used to smelt ferrovanadium, vanadium-nitrogen alloy and other products, but for some specific application fields (such as electrolyte, etc.), the chromium and potassium content in vanadium oxide is required to be controlled at a low level. The existing acidic ammonium salt vanadium precipitation process cannot meet the technical requirements for the preparation of low-chromium and low-potassium vanadium oxide from sodium vanadium liquid.

[0003] There are few existing studies on the problem of high potassium content in vanadium oxide products. However, there are reports on the high chromium content in vanadium oxide products, which involve the precipitation of vanadium after removing chromium from vanadium-containing solutions. For example, Chinese patent No. CN117682556A discloses a method for preparing low-chromium ammonium polyvanadate, which selectively reduces chromium with hydrogen peroxide under acidic conditions, and then adds triethanolamine to complex trivalent chromium to obtain low-chromium ammonium polyvanadate. This method can reduce the chromium content of vanadium products, but cannot solve the problem of high potassium content.

[0004] A Chinese patent with publication number CN118726770A discloses a method for selectively reducing chromium and silicon by sodium vanadium solution. Under alkaline conditions, sodium hydrosulfide or sodium sulfide is used as a chromium removal agent and hydrogen peroxide is used as an oxidant to remove chromium and oxidize the sodium vanadium solution. Then, ammonium salt is added to precipitate ammonium metavanadate to obtain a low-chromium and low-potassium vanadium product. The patent does not involve the relevant content of ammonium salt and vanadium recovery from vanadium precipitation wastewater. There are problems such as large amount of ammonium salt and relatively low vanadium yield. Moreover, the vanadium precipitation wastewater is directly mixed with the chromium-containing sodium vanadium solution to precipitate vanadium with acidic ammonium salt. Because excessive chromium removal agent and hydrogen peroxide will reduce hexavalent chromium, the chromium content of the vanadium product will increase significantly, resulting in that the vanadium precipitation wastewater cannot be directly mixed with the chromium-containing sodium vanadium solution for use.

[0005] On the basis of the above patented technology, the problem of how to recover the ammonium salt and vanadium in the vanadium precipitation wastewater while preparing low-chromium and low-potassium vanadium products needs to be solved. Summary of the invention

[0006] The technical problem solved by the present invention is to provide a method for preparing low-chromium and low-potassium vanadium oxide using sodium vanadium solution. The method provided in the present application can control the content of chromium and potassium in vanadium oxide and realize the recycling of ammonium salt in vanadium precipitation wastewater.

[0007] In view of this, the present application provides a method for preparing low-chromium and low-potassium vanadium oxide using sodium vanadium solution, comprising the following steps:

[0008] S1) adjusting the pH of the sodium vanadium solution to 10.5-11.0, and then reacting with a chromium removal agent to obtain an initial chromium removal slurry; the chromium removal agent is selected from one or both of sodium sulfide and sodium hydrosulfide;

[0009] S2) adjusting the pH of the initial chromium removal slurry to 9.0-9.5, reacting with a silicon removal agent, and obtaining a filtrate after solid-liquid separation;

[0010] S3) reacting the filtrate with hydrogen peroxide, adding ammonium salt, and obtaining ammonium metavanadate and primary vanadium precipitation wastewater after solid-liquid separation after vanadium precipitation;

[0011] S4) adjusting the pH of the primary vanadium precipitation wastewater to 6-7, reacting it with ferrous sulfate, adding a complexing agent, mixing it with sodium vanadium solution for precipitation, and then separating the solid and liquid to obtain ammonium polyvanadate and secondary vanadium precipitation wastewater; the complexing agent is selected from one or more of disodium ethylenediaminetetraacetate, tetrasodium ethylenediaminetetraacetate and triethanolamine;

[0012] The ammonium metavanadate is oxidized and calcined to obtain low-chromium and low-potassium vanadium oxide.

[0013] Preferably, the sodium vanadium solution is obtained by high-temperature roasting and water leaching of vanadium slag and sodium salt, and the Cr concentration in the sodium vanadium solution is greater than 1 g / L, the Si concentration is greater than 0.5 g / L, and the K concentration is greater than 0.1 g / L.

[0014] Preferably, in step S1), the chromium removal agent is added according to a molar ratio of S to Cr of (0.75-1.0):1; the pH adjusting agent is sulfuric acid or sodium hydroxide, the reaction temperature is 60-100°C, and the reaction time is 30-90 minutes.

[0015] Preferably, in step S2), the reagent for adjusting pH is sulfuric acid, the desiliconizing agent is selected from one or both of aluminum sulfate and sodium aluminate, the desiliconizing agent is added in an amount according to a molar ratio of Al:Si of (0.5-1.0):1, the reaction temperature is 30-100°C, and the reaction time is 10-100 min.

[0016] Preferably, in step S3), the filtrate is cooled by 30 to 40° C. and then reacted with hydrogen peroxide for 20 to 60 minutes.

[0017] Preferably, in step S3), the amount of hydrogen peroxide added is according to the molar ratio of H2O2:Cr=(2-3):1; the ammonium salt is selected from ammonium sulfate, and the amount of ammonium salt added is according to the mass ratio of (NH4)2SO4 / V=(3-4):1, and the vanadium precipitation time is 2-5h.

[0018] Preferably, in step S4), the temperature of the reaction with ferrous sulfate is 80-100° C. and the time is 30-120 min.

[0019] Preferably, in step S4), the amount of ferrous sulfate used is based on the amount of Fe in the solution after adjusting the pH. 2+ Add at a concentration of 0.05-0.10 g / L.

[0020] Preferably, in step S4), after mixing with the sodium vanadium solution, sulfuric acid is added to adjust the pH to 1.6-2.0, and the amount of the complexing agent added is 0.01-0.05 mol / L of the sodium vanadium solution.

[0021] Preferably, in step S4), the precipitation temperature is 90-100° C. and the precipitation time is 40-60 min.

[0022] The present application provides a method for preparing low-chromium and low-potassium vanadium oxide by using sodium vanadium solution. The method comprises the following steps: firstly adjusting the pH value of the sodium vanadium solution to 10.5-11.0, reacting with a chromium removal agent to achieve precipitation of chromium in the sodium vanadium solution, adjusting the pH value of the initial chromium removal slurry to fully precipitate chromium hydroxide, reacting with a silicon removal agent to achieve deep silicon removal, reacting the filtrate obtained after solid-liquid separation with hydrogen peroxide to oxidize excess sulfide ions, adding ammonium salt to precipitate ammonium metavanadate under weak alkaline conditions, and then decomposing the hydrogen peroxide in the obtained primary vanadium precipitation wastewater, precipitating vanadium and removing impurities such as chromium and iron, finally obtaining ammonium polyvanadate and secondary vanadium precipitation wastewater, realizing the recovery and utilization of ammonium salt and vanadium in the primary vanadium precipitation wastewater, and oxidizing and calcining the ammonium metavanadate to obtain low-chromium and low-potassium vanadium oxide. DETAILED DESCRIPTION

[0023] In order to further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the claims of the present invention.

[0024] In view of the problems of high chromium and potassium content in vanadium oxide products and recycling of ammonium salts and vanadium in vanadium precipitation wastewater in the prior art, the present application provides a method for preparing low-chromium and low-potassium vanadium oxide using sodium vanadium solution. The method provided by the present application can control the chromium and potassium content in the vanadium oxide product while also recycling the ammonium salt in the vanadium precipitation wastewater. Specifically, the embodiment of the present invention discloses a method for preparing low-chromium and low-potassium vanadium oxide using sodium vanadium solution, comprising the following steps:

[0025] S1) adjusting the pH of the sodium vanadium solution to 10.5-11.0, and then reacting with a chromium removal agent to obtain an initial chromium removal slurry;

[0026] S2) adjusting the pH of the initial chromium removal slurry to 9.0-9.5, reacting with a silicon removal agent, and obtaining a filtrate after solid-liquid separation;

[0027] S3) reacting the filtrate with hydrogen peroxide, adding ammonium salt, and obtaining ammonium metavanadate and primary vanadium precipitation wastewater after solid-liquid separation after vanadium precipitation;

[0028] S4) adjusting the pH of the primary vanadium precipitation wastewater to 6-7, reacting it with ferrous sulfate, adding a complexing agent, mixing it with sodium vanadium solution for precipitation, and then separating the solid and liquid to obtain ammonium polyvanadate and secondary vanadium precipitation wastewater;

[0029] The ammonium metavanadate is oxidized and calcined to obtain low-chromium and low-potassium vanadium oxide.

[0030] In the method of preparing low-chromium and low-potassium vanadium oxide in the present application, the pH of the sodium vanadium solution is first adjusted to 10.5-11.0, and then reacted with a chromium removal agent to obtain an initial chromium-removed slurry; in this process, the sodium vanadium solution is obtained by high-temperature roasting and water leaching of vanadium slag and sodium salt, wherein the vanadium slag is obtained by oxidative blowing of vanadium-containing molten iron; the Cr concentration in the sodium vanadium solution is greater than 1g / L, the Si concentration is greater than 0.5g / L, and the K concentration is greater than 0.1g / L. Since the above process reacts with the chromium removal agent, that is, the process of reducing chromium, reducing Na2S2O3 will be generated in this process, and vanadium and chromium (with Cr) will be further reduced in the acidic ammonium salt precipitation process. 6+ ), resulting in vanadium loss and increased chromium content in vanadium products. Therefore, the chromium removal solution needs to be oxidized before returning to the acidic ammonium salt vanadium precipitation system. Due to the high initial pH of the chromium removal reaction and the large amount of hydroxide produced during the reduction chromium removal process, the pH of the slurry after chromium removal is high. Chromium hydroxide is amphoteric and is not fully precipitated and has fine particles under strong alkaline conditions; therefore, sulfuric acid is used to adjust the initial chromium removal slurry pH to 9.0-9.5 to facilitate the sufficient precipitation of chromium. The reagent for adjusting the pH of the sodium vanadium solution is sulfuric acid or sodium hydroxide, the chromium removal agent is selected from one or both of sodium sulfide and sodium hydrosulfide, the chromium removal agent is added according to the molar ratio of S to Cr of (0.75-1.0):1, the reaction temperature is 60-100°C, and the reaction time is 30-90min; specifically, the chromium removal agent is added according to the molar ratio of S to Cr of (0.8-0.9):1, the reaction temperature is 70-90°C, and the reaction time is 50-80min; the chemical reaction formula of the above reaction is specifically: 8CrO4 2- +6S 2- +23H2O=8Cr(OH)3↓+3S2O3 2- +22OH - .

[0031] The present application then adjusts the pH of the initial chromium removal slurry to 9.0-9.5, and then reacts with a silicon removal agent, and obtains a filtrate after solid-liquid separation; in the above process, the reagent for adjusting the pH is preferably sulfuric acid, so that the chromium hydroxide in the slurry is fully precipitated, and the above pH range is conducive to deep silicon removal of aluminum salts. The silicon removal agent is selected from one or both of aluminum sulfate and sodium aluminate, and the amount of the silicon removal agent added is according to the molar ratio of Al:Si (0.5-1.0):1, the temperature of the reaction is 30-100°C, and the time is 10-100min; specifically, the amount of the silicon removal agent added is according to the molar ratio of Al:Si (0.6-0.8):1, the temperature of the reaction is 40-80°C, and the time is 30-80min.

[0032] According to the present invention, the filtrate obtained above is then reacted with hydrogen peroxide, and then ammonium salt is added to precipitate ammonium metavanadate, and ammonium metavanadate and primary vanadium precipitation wastewater are obtained after solid-liquid separation; in the above process, the filtrate is preferably cooled to 30-40°C and then reacted with hydrogen peroxide for 20-60 minutes, specifically 30-50 minutes. The reaction of the filtrate and hydrogen peroxide mainly oxidizes excess sodium sulfide, sodium hydrosulfide and sodium thiosulfate generated during the reaction. Since hydrogen peroxide is easily decomposed under alkaline conditions, it is difficult to fully oxidize sodium sulfide, sodium hydrosulfide and sodium thiosulfate by accurate measurement, so adding excess hydrogen peroxide is an effective means to ensure that low-valent sulfur is fully oxidized. Add ammonium salt to the oxidized solution, and precipitate ammonium metavanadate under weak alkaline conditions. Since potassium ions have stronger binding ability with vanadate ions than ammonium ions, the potassium content of the vanadium product can be reduced by increasing the amount of ammonium salt used for vanadium precipitation (the amount of ammonium salt used for ammonium metavanadate precipitation is 3 to 4 times that of acidic ammonium salt vanadium precipitation); since the chromium in the solution has been removed, the chromium content in the obtained ammonium metavanadate is also low. The wastewater from the precipitation of ammonium metavanadate has a high concentration of ammonium salt and vanadium (the vanadium concentration of the wastewater from the precipitation of ammonium metavanadate is about 3 to 6 times that of the wastewater from the precipitation of acidic ammonium salt vanadium precipitation), and contains excessive hydrogen peroxide; after solid-liquid separation, ammonium metavanadate and primary vanadium precipitation wastewater are obtained. The amounts of the hydrogen peroxide and the ammonium salt added are both excessive, and the amount of the hydrogen peroxide added is according to the molar ratio of H2O2:Cr=(2-3):1; the ammonium salt is selected from ammonium sulfate, and the amount of the ammonium salt added is according to the mass ratio of (NH4)2SO4 / V=(3-4):1, and the vanadium precipitation time is 2-5h.

[0033] This application finally recycles the primary vanadium precipitation wastewater, that is, the pH of the primary vanadium precipitation wastewater is adjusted to 6-7, and then reacted with ferrous sulfate, and then a chelating agent is added, mixed with sodium vanadium liquid for precipitation, and then solid-liquid separation is performed to obtain ammonium polyvanadate and secondary vanadium precipitation wastewater. In the above process, the pH of the primary vanadium precipitation wastewater is adjusted to 6-7 in order to avoid ammonia loss caused by ammonia volatilization during the subsequent heating process and affect the operating environment, and to control the pH as high as possible to facilitate the decomposition of hydrogen peroxide. Adding ferrous sulfate and increasing the temperature of the wastewater are intended to accelerate the decomposition rate of excess hydrogen peroxide and reduce the residual proportion of hydrogen peroxide in the wastewater; at the same time, the temperature of acidic ammonium salt vanadium precipitation is generally 95°C, and heating the wastewater can also shorten the heating time of vanadium precipitation. Then, the chelating agent disodium ethylenediaminetetraacetic acid, tetrasodium ethylenediaminetetraacetic acid or triethanolamine is added to react with Cr 3+ , Fe 3+ Impurity ions such as hydrogen peroxide form soluble complexes to avoid the problem of increased chromium content in vanadium products due to insufficient decomposition of hydrogen peroxide and reduction of chromium under acidic conditions. After decomposing hydrogen peroxide, it is mixed with sodium vanadium liquid as an ammonium salt to precipitate ammonium polyvanadate, which can be used to fully utilize the ammonium salt and further recover vanadium. In the above process, the temperature of the reaction with ferrous sulfate is 80-100°C and the time is 30-120 minutes. Specifically, the temperature of the reaction is 90-95°C and the time is 40-80 minutes. The amount of ferrous sulfate used is based on the amount of Fe in the solution after adjusting the pH. 2+ The concentration is 0.05-0.10 g / L. Specifically, the amount of ferrous sulfate is based on the amount of Fe in the solution after adjusting the pH. 2+ The concentration is 0.06-0.08 g / L. After mixing with the sodium vanadium solution, sulfuric acid is added to adjust the pH to 1.6-2.0, and the amount of the complexing agent added is 0.01-0.05 mol / L of the sodium vanadium solution. Specifically, after mixing with the sodium vanadium solution, sulfuric acid is added to adjust the pH to 1.7-1.9, and the amount of the complexing agent added is 0.02-0.04 mol / L of the sodium vanadium solution; the temperature of the precipitation is 90-100°C, and the time is 40-60 minutes.

[0034] Aiming at the problem that the vanadium product obtained by using acidic ammonium salt to precipitate vanadium from sodium vanadium liquid has high chromium and potassium contents, the present invention provides a method for preparing low-chromium and low-potassium vanadium oxide from sodium vanadium liquid. The method utilizes a selective reduction to remove chromium-precipitate ammonium metavanadate process to prepare the low-chromium and low-potassium vanadium product; and the high-ammonium and high-vanadium wastewater after the precipitation of ammonium metavanadate is used as ammonium salt for recycling in the production of common vanadium oxide, thereby reducing the comprehensive production cost of vanadium oxide, and has good industrialization prospects.

[0035] In order to further understand the present invention, the method for preparing low-chromium and low-potassium vanadium oxide by using sodium vanadium solution provided by the present invention is described in detail below in conjunction with examples. The protection scope of the present invention is not limited by the following examples.

[0036] Example 1

[0037] Take 400mL of sodium vanadium solution (V 43.53g / L, Si 1.02g / L, Cr 3.29g / L, Na37.45g / L, K 0.37g / L and pH=10.27 (60℃)), heat it to 60℃ in a water bath, adjust the solution pH to 10.58 with solid sodium hydroxide, then add 5.47g of sodium sulfide (Na2S·9H2O) to reduce chromium, and stir to react for 60min; after the chromium reduction reaction is completed, adjust the slurry pH to 9.2 with sulfuric acid, add 3.88g of aluminum sulfate (Al2(SO4)3·18H2O) and stir to react for 30min, after the desiliconization reaction is completed, separate the solid and liquid, and add water to wash and remove impurities, and obtain 426mL of filtrate (containing filtrate and washing water), whose chemical composition is V 40.18g / L, Si<0.01g / L and Cr 0.003g / L; the solution after silicon and chromium removal was cooled to 30°C, 6mL of 30% hydrogen peroxide was added, and the oxidation reaction was carried out for 30min; 52g of ammonium sulfate was added, and the reaction was stirred for 2.5h, and the solid-liquid separation and washing of ammonium metavanadate were carried out to obtain 37.09g of ammonium metavanadate and 448mL of primary vanadium precipitation wastewater (including filtrate and washing water, V2.26g / L and NH4 + 18.92g / L); ammonium metavanadate was oxidized and calcined at 550℃ for 4h to obtain low-chromium and low-potassium vanadium pentoxide (V2O5 99.79%, Si 0.013%, Cr<0.01%, K0.021% and Na0.030%);

[0038] The pH value of the primary vanadium precipitation wastewater is adjusted to 6.28 by sulfuric acid, 0.14 g of ferrous sulfate (FeSO4·7H2O) is added, and the mixture is heated to 90° C. in a water bath and kept at a constant temperature for 90 min. After the decomposition reaction of hydrogen peroxide in the primary vanadium precipitation wastewater is completed, 1.8 g of disodium ethylenediaminetetraacetate and 680 mL of sodium vanadium solution are added, and sulfuric acid is added after mixing to adjust the pH value of the mixed solution to 1.8-1.9. The mixture is heated to 95° C. in a water bath and kept at a constant temperature for 60 min. After the vanadium precipitation reaction is completed, solid-liquid separation is performed to obtain ammonium polyvanadate (V 50.12%, Si 0.11%, Cr 0.07%, K 0.16% and Na 0.22%) and secondary vanadium precipitation wastewater (V 0.24 g / L); the secondary vanadium precipitation wastewater enters a wastewater treatment system.

[0039] Example 2

[0040] Take 400mL of sodium vanadium solution (V 41.96g / L, Si 1.18g / L, Cr 3.12g / L, Na38.37g / L, K 0.54g / L and pH=10.32 (60°C)), heat it in a water bath to 65°C, adjust the solution pH to 10.54 with solid sodium hydroxide, then add 1.54g of sodium hydrosulfide (NaHS content 70%) to reduce chromium, and stir to react for 40min; after the chromium reduction reaction is completed, adjust the slurry pH to 9.4 with sulfuric acid, add 3.88g of aluminum sulfate (Al2(SO4)3·18H2O) and stir to react for 60min, after the desiliconization reaction is completed, separate the solid and liquid, and add water to wash and remove impurities, and obtain 433mL of filtrate (containing filtrate and washing water), whose chemical composition is V 38.22g / L, Si<0.01g / L and Cr 0.004g / L; the solution after silicon and chromium removal was cooled to 35°C, 6.8mL of 30% hydrogen peroxide was added, and the oxidation reaction was carried out for 60min; 58g of ammonium sulfate was added, and the reaction was stirred for 3h, and the solid-liquid separation and washing of ammonium metavanadate were carried out to obtain 36.25g of ammonium metavanadate and 445mL of primary vanadium precipitation wastewater (containing filtrate and washing water, V1.87g / L and NH4 + 22.98g / L); ammonium metavanadate was oxidized and calcined at 550℃ for 4h to obtain low-chromium and low-potassium vanadium pentoxide (V2O5 99.81%, Si 0.013%, Cr<0.01%, K0.018% and Na0.028%);

[0041] The pH value of the primary vanadium precipitation wastewater is adjusted to 6.72 by sulfuric acid, 0.22 g of ferrous sulfate (FeSO4·7H2O) is added, and the mixture is heated to 85° C. and kept at the constant temperature for 120 min. After the decomposition reaction of hydrogen peroxide in the primary vanadium precipitation wastewater is completed, 2.5 g of tetrasodium ethylenediaminetetraacetic acid and 850 mL of sodium vanadium solution are added, and sulfuric acid is added after mixing to adjust the pH value of the mixed solution to 1.8-1.9. The mixture is heated to 95° C. and kept at the constant temperature for 60 min. After the vanadium precipitation reaction is completed, the solid and liquid are separated to obtain ammonium polyvanadate (V 50.02%, Si 0.10%, Cr 0.06%, K 0.18% and Na 0.24%) and secondary vanadium precipitation wastewater (V 0.22 g / L); the secondary vanadium precipitation wastewater enters the wastewater treatment system.

[0042] Example 3

[0043] 400 mL of sodium vanadium solution (V 44.55 g / L, Si 1.27 g / L, Cr 2.98 g / L, Na 39.15 g / L, K 0.59 g / L and pH = 10.08 (60 ° C)) was taken and heated to 70 ° C in a water bath. The solution pH was adjusted to 10.72 using solid sodium hydroxide, and then 5.22 g of sodium sulfide (Na2S·9H2O) was added to reduce chromium and stirred for 80 minutes. After the chromium reduction reaction was completed, the slurry pH was adjusted to 9.1 using sulfuric acid, and 1.34 g of sodium aluminate (NaAlO2) was added and stirred for 90 minutes. After the desiliconization reaction was completed, the solid and liquid were separated, and water was added to wash and remove impurities. A total of 436 mL of filtrate (containing filtrate and washing water) was obtained, and its chemical composition was V 40.13 g / L, Si <0.01 g / L and Cr 0.002g / L; the solution after silicon and chromium removal was cooled to 37°C, 7.4mL of 30% hydrogen peroxide was added, and the oxidation reaction was carried out for 45min; 68g of ammonium sulfate was added, and the reaction was stirred for 4h, and the solid-liquid separation and washing of ammonium metavanadate were carried out to obtain 38.82g of ammonium metavanadate and 452mL of primary vanadium precipitation wastewater (including filtrate and washing water, V1.54g / L and NH4 + 27.78g / L); ammonium metavanadate was oxidized and calcined at 550℃ for 4h to obtain low-chromium and low-potassium vanadium pentoxide (V2O5 99.76%, Si 0.012%, Cr<0.01%, K0.015% and Na 0.026%);

[0044] The pH value of the primary vanadium precipitation wastewater is adjusted to 6.28 by sulfuric acid, and 0.20 g of ferrous sulfate (FeSO4·7H2O) is added, and the mixture is heated to 95° C. in a water bath and kept at a constant temperature for 30 min. After the decomposition reaction of hydrogen peroxide in the primary vanadium precipitation wastewater is completed, 1.35 g of triethanolamine and 950 mL of sodium vanadium solution are added, and sulfuric acid is added after mixing to adjust the pH value of the mixed solution to 1.8-1.9, and the mixture is heated to 95° C. in a water bath and kept at a constant temperature for 60 min. After the vanadium precipitation reaction is completed, solid-liquid separation is performed to obtain ammonium polyvanadate (V 50.08%, Si 0.11%, Cr 0.06%, K 0.18% and Na 0.25%) and secondary vanadium precipitation wastewater (V 0.22 g / L); the secondary vanadium precipitation wastewater enters the wastewater treatment system.

[0045] In summary, the present invention utilizes sodium vanadium solution to prepare low-chromium and low-potassium vanadium oxide, while realizing the recovery and utilization of ammonium salt and vanadium in primary vanadium precipitation wastewater, thereby reducing the comprehensive production cost of vanadium oxide.

[0046] The above embodiments are only used to help understand the method and core idea of ​​the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

[0047] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing low-chromium and low-potassium vanadium oxide using sodium vanadium solution, comprising the following steps: S1) adjusting the pH of the sodium vanadium solution to 10.5-11.0, and then reacting with a chromium removal agent to obtain an initial chromium removal slurry; the chromium removal agent is selected from one or both of sodium sulfide and sodium hydrosulfide; S2) adjusting the pH of the initial chromium removal slurry to 9.0-9.5, reacting with a silicon removal agent, and obtaining a filtrate after solid-liquid separation; S3) reacting the filtrate with hydrogen peroxide, adding ammonium salt, and obtaining ammonium metavanadate and primary vanadium precipitation wastewater after solid-liquid separation after vanadium precipitation; S4) adjusting the pH of the primary vanadium precipitation wastewater to 6-7, reacting it with ferrous sulfate, adding a complexing agent, mixing it with sodium vanadium solution for precipitation, and then separating the solid and liquid to obtain ammonium polyvanadate and secondary vanadium precipitation wastewater; the complexing agent is selected from one or more of disodium ethylenediaminetetraacetate, tetrasodium ethylenediaminetetraacetate and triethanolamine; The ammonium metavanadate is oxidized and calcined to obtain low-chromium and low-potassium vanadium oxide.

2. The method according to claim 1, characterized in that The sodium vanadium solution is obtained by high-temperature roasting and water immersion of vanadium slag and sodium salt. The Cr concentration in the sodium vanadium solution is greater than 1 g / L, the Si concentration is greater than 0.5 g / L, and the K concentration is greater than 0.1 g / L.

3. The method according to claim 1, characterized in that In step S1), the chromium removal agent is added according to the molar ratio of S to Cr of (0.75-1.0):1; the reagent for adjusting pH is sulfuric acid or sodium hydroxide, the reaction temperature is 60-100°C, and the reaction time is 30-90 minutes.

4. The method according to claim 1, characterized in that: In step S2), the reagent for adjusting pH is sulfuric acid, the desiliconizing agent is selected from one or both of aluminum sulfate and sodium aluminate, the amount of the desiliconizing agent added is according to the molar ratio of Al:Si of (0.5-1.0):1, the reaction temperature is 30-100°C, and the reaction time is 10-100 min.

5. The method according to claim 1, characterized in that In step S3), the filtrate is cooled by 30-40°C and then reacted with hydrogen peroxide for 20-60 minutes.

6. The method according to claim 1, characterized in that In step S3), the amount of hydrogen peroxide added is according to the molar ratio of H2O2:Cr=(2-3):1; the ammonium salt is selected from ammonium sulfate, and the amount of ammonium salt added is according to the mass ratio of (NH4)2SO4 / V=(3-4):1, and the vanadium precipitation time is 2-5h.

7. The method according to claim 1, characterized in that In step S4), the temperature of the reaction with ferrous sulfate is 80-100° C. and the time is 30-120 min.

8. The method according to claim 1, characterized in that In step S4), the amount of ferrous sulfate used is based on the amount of Fe in the solution after adjusting the pH. 2+ Add at a concentration of 0.05-0.10 g / L.

9. The method according to claim 1, characterized in that: In step S4), after mixing with the sodium vanadium solution, sulfuric acid is added to adjust the pH to 1.6-2.0, and the amount of the complexing agent added is 0.01-0.05 mol / L of the sodium vanadium solution.

10. The method according to claim 1, characterized in that In step S4), the precipitation temperature is 90-100° C. and the precipitation time is 40-60 min.