Method for extracting vanadium through direct oxidation and acid leaching of vanadium slag

Abstract

The invention discloses a method for extracting vanadium by direct oxidation and acid leaching of vanadium slag, which comprises the following steps: crushing and grinding the vanadium slag, and screening to obtain fine particle vanadium slag less than 200 meshes; sulfuric acid and an oxidizing agent are mixed in proportion and evenly stirred, and a mixed leaching agent is obtained; and under the heating and stirring conditions, a mixed leaching agent is added into the fine-particle vanadium slag for a leaching reaction, solid-liquid separation is conducted after the reaction is completed, and vanadium-containing leachate is obtained. According to the method, the traditional wrapping phase destroying and target element leaching processes which need to be completed step by step or under harsh conditions are integrated into a low-temperature sulfuric acid agitation leaching process, so that the technological process is remarkably shortened; on the premise that impurities are not introduced by the strong oxidant, low-energy-consumption efficient leaching of the vanadium slag at normal pressure can be achieved, and the vanadium leaching rate can reach 90% or above.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of vanadium extraction, in particular to a method for directly oxidizing and acid leaching vanadium from vanadium slag. BACKGROUND

[0002] Vanadium is a rare strategic resource. Vanadium slag obtained by blast furnace-converter smelting of vanadium-titanium magnetite is the main raw material for vanadium extraction in China. The industrial vanadium slag is mainly composed of spinel phase and silicate inclusions such as olivine phase and pyroxene phase. Oxidation roasting or harsh oxidation acid leaching is usually required to effectively destroy the silicate inclusions and convert vanadium spinel into solution. However, the existing vanadium extraction methods have problems such as long process, high energy consumption, and the like. Therefore, it is very important to develop a low-energy green and efficient vanadium extraction process.

[0003] Vanadium spinel has a stable structure. High-temperature oxidation roasting of vanadium slag is an economically viable method for vanadium extraction, and a mature sodium roasting-water leaching process and calcium roasting-acid leaching process have been formed. However, the reaction of vanadium slag with additives in this process needs to be carried out at a high temperature of more than 750 to 900℃, and a large amount of toxic and harmful gas is discharged. In addition, the tailings after vanadium extraction contain a high content of residual alkali metal, which is difficult to be directly recycled. In order to avoid high-energy roasting process, a direct acid leaching method for vanadium extraction has also been developed. For example, CN104674015B discloses a fluidized wet method for vanadium extraction from vanadium slag. The vanadium slag is placed in a fluidized reactor with high-concentration sulfuric acid and air is introduced to achieve fluidized extraction of vanadium at a certain temperature. However, this process requires a fluidized device, which often faces problems such as poor fluidity and easy clogging, large equipment investment, and difficult equipment selection, which brings great challenges to production efficiency and product quality. CN114438346A discloses a normal-pressure acid leaching method for vanadium extraction. The vanadium slag is mechanically activated in a synergistic strengthening leaching agent and then acid leached in high-concentration sulfuric acid to achieve vanadium extraction. However, the synergistic reagents such as sodium nitrate, manganese dioxide, and potassium permanganate are introduced as impurities into the vanadium solution, increasing the cost of subsequent vanadium recovery. CN104164571B discloses a pressurized acid leaching method for vanadium extraction from vanadium slag. The vanadium slag must be efficiently leached under pressurized conditions. The energy consumption of pressurized leaching is high, the leaching equipment is expensive, and the application of high pressure also has production safety problems.

[0004] In summary, the existing vanadium slag extraction processes generally have problems such as complex process, high energy consumption, and harsh equipment requirements or the introduction of impurities. Therefore, how to provide a new method for efficient and green vanadium extraction under mild conditions is a technical problem that needs to be solved by those skilled in the art. SUMMARY

[0005] In view of the above problems in the prior art, the purpose of the present application is to provide a method for directly oxidizing and acid leaching vanadium from vanadium slag, which solves the problems of complex process, high energy consumption, and harsh equipment requirements in the existing vanadium slag extraction processes.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A method for direct oxidative acid leaching of vanadium from vanadium slag, characterized by comprising the following steps:

[0008] a. After crushing and grinding the vanadium slag, it is sieved to obtain fine vanadium slag particles smaller than 200 mesh;

[0009] b. Mix sulfuric acid and oxidant solution in a certain proportion and stir evenly to prepare a mixed leaching agent solution;

[0010] c. Under heating and stirring conditions, a mixed leaching agent is added to the fine vanadium slag to carry out a leaching reaction. After the reaction is completed, solid-liquid separation is performed to obtain a vanadium-containing leachate.

[0011] Furthermore, in step a, the main phases of the vanadium slag are spinel, olivine and pyroxene, which are industrial vanadium slags obtained by blast furnace-converter smelting, and are abundant and low in cost.

[0012] Furthermore, in step b, the sulfuric acid concentration in the leaching agent solution is 3–5 mol / L, and the oxidant concentration is 0.6–1.0 mol / L. The mixed leaching agent solution is prepared according to a sulfuric acid to oxidant molar ratio of 3:1–5:0.8. This concentration is particularly critical for the low-temperature sulfuric acid stirring leaching process.

[0013] Furthermore, in step c, a mixed leaching agent is added to the vanadium slag at a liquid-to-solid ratio of 4:1 to 10:1, the leaching temperature is 30 to 90°C, the leaching time is 0.5 to 3 hours, and after leaching, a vacuum filtration device is used to separate the solid and liquid to obtain a vanadium-containing leachate.

[0014] To further improve the vanadium extraction rate, it is preferable to add a mixed leaching agent to the vanadium slag at a liquid-to-solid ratio of 6:1 to 10:1, with a leaching temperature of 70 to 90°C and a leaching time of 1.5 to 3 hours. After leaching, a vacuum filtration device is used to separate the solid and liquid to obtain a vanadium-containing leachate.

[0015] Furthermore, the oxidant can be any one of hydrogen peroxide, ClO2, sodium persulfate, sodium hypochlorite, or sodium chlorite. Any oxidant that is low in cost and easy to operate can be selected.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] 1. This invention introduces an external strong oxidant and prepares a mixed leaching agent solution for leaching reaction, simultaneously oxidizing low-valent iron, vanadium, and other elements in vanadium slag. The chemical stress generated by their valence state transformation disrupts the stable structure of the silicate-encapsulated phase, thereby efficiently dissociating the encapsulated vanadium-containing spinel and accelerating its dissolution. This method integrates the traditionally separate or harsh "phase destruction" and "target element leaching" processes into a single low-temperature sulfuric acid stirring leaching step, significantly shortening the process flow. The strong oxidant, hydrogen peroxide, enables low-energy, high-efficiency leaching of vanadium slag under normal pressure without introducing impurities, achieving a vanadium leaching rate of over 90%.

[0018] 2. This invention breaks through the dependence of current processes on high temperature, high pressure or step-by-step processing, which not only greatly simplifies the process flow and reduces energy consumption and equipment requirements, but also avoids the introduction of impurities and tailings pollution. It fundamentally solves the problems of high energy consumption and low energy utilization in industrial technology, and provides an effective solution for green and efficient vanadium extraction; it has the characteristics of low energy consumption and high efficiency. Detailed Implementation

[0019] The specific embodiments of the present invention will be described in further detail below with reference to specific examples.

[0020] The numerical ranges in this invention should be understood to also specifically disclose each intermediate value between the upper and lower limits of the range. Each smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0021] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail. The terms “comprising,” “including,” “having,” “containing,” etc., as used herein are open-ended, meaning that they include but are not limited to.

[0022] Unless otherwise specified, the experimental methods used in this invention are all conventional methods.

[0023] Unless otherwise specified, all materials and reagents used in this invention can be purchased or synthesized by known methods.

[0024] The following provides a detailed description of specific embodiments of the present invention. Those skilled in the art should understand that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the invention. Therefore, substitutions and modifications can be made to the above examples without departing from the spirit and scope of the claims.

[0025] I. The main chemical composition of the vanadium slag sample is shown in Table 1.

[0026] Ingredients MgO Al2O3 SiO2 CaO TiO2 [V2O5] Cr2O3 MnO Fe2O3 Content 2.77 3.35 15.16 2.38 10.44 14.31 3.03 7.25 41.02

[0027] II. Experimental conditions and parameters for Examples 1-3

[0028] Example 1

[0029] A method for direct oxidative acid leaching of vanadium from vanadium slag includes the following steps:

[0030] The vanadium slag was crushed and sieved to obtain 200-mesh powder. An appropriate amount (e.g., 3g) was weighed and placed in a three-necked flask. Then, the leaching agent solution was prepared: 4 mol / L sulfuric acid and 1 mol / L hydrogen peroxide were prepared, and a mixed leaching agent solution was prepared at a molar ratio of sulfuric acid to hydrogen peroxide of 4:1.

[0031] A three-necked flask containing vanadium slag was placed in a water bath and heated to 90°C with a stirring speed of 200 rpm. A leaching agent solution was added to the flask at a liquid-to-solid ratio of 8:1 (ml / g) between the sulfuric acid-hydrogen peroxide mixed leaching agent solution and the vanadium slag powder. Leaching was carried out with continuous stirring for 3 hours. After the reaction was complete, vacuum filtration was performed, and the residue was washed three times with deionized water. The filtrate was collected and subjected to ICP analysis; the vanadium leaching rate was 95.50%.

[0032] Example 2

[0033] A method for direct oxidative acid leaching of vanadium from vanadium slag includes the following steps:

[0034] The vanadium slag was crushed and sieved to obtain 200-mesh powder. An appropriate amount (e.g., 3g) was weighed and placed in a three-necked flask. Then, the leaching agent solution was prepared: 4 mol / L sulfuric acid and 0.8 mol / L hydrogen peroxide were prepared, and a mixed leaching agent solution was prepared according to the molar ratio of sulfuric acid to hydrogen peroxide of 4:0.8.

[0035] A three-necked flask containing vanadium slag was placed in a water bath and heated to 90°C with a stirring speed of 200 rpm. A leaching agent solution was added to the flask at a liquid-to-solid ratio of 8:1 (ml / g) between the sulfuric acid-hydrogen peroxide mixed leaching agent solution and the vanadium slag powder. Leaching was carried out with continuous stirring for 3 hours. After the reaction was completed, the mixture was vacuum filtered, and the residue was washed three times with deionized water. The filtrate was collected and subjected to ICP analysis, showing a vanadium leaching rate of 94.98%.

[0036] Example 3

[0037] A method for direct oxidative acid leaching of vanadium from vanadium slag includes the following steps:

[0038] The vanadium slag was crushed and sieved to obtain 200-mesh powder. An appropriate amount (e.g., 3g) was weighed and placed in a three-necked flask. Then, the leaching agent solution was prepared: 5 mol / L sulfuric acid and 0.8 mol / L hydrogen peroxide were prepared, and a mixed leaching agent solution was prepared according to the molar ratio of sulfuric acid to hydrogen peroxide of 5:0.8.

[0039] A three-necked flask containing vanadium slag was placed in a water bath and heated to 90°C with a stirring speed of 200 rpm. A leaching agent solution was added to the flask at a liquid-to-solid ratio of 8:1 (ml / g) between sulfuric acid-hydrogen peroxide mixed leaching agent solution and vanadium slag powder, and leaching was carried out with continuous stirring for 3 hours. After the reaction was completed, vacuum filtration was performed, and the residue was washed three times with deionized water. The filtrate was collected and subjected to ICP analysis; the vanadium leaching rate was 96.83%.

[0040] Comparative Example 1

[0041] The vanadium slag was crushed and sieved to obtain 200-mesh powder. An appropriate amount (e.g., 3g) was weighed and placed in a three-necked flask. Then, a leaching agent solution was prepared: a 4mol / L sulfuric acid solution.

[0042] A three-necked flask containing vanadium slag was placed in a water bath and heated to 90°C with a stirring speed of 200 rpm. A sulfuric acid solution was added to the flask at a liquid-to-solid ratio of 8:1 (ml / g) of sulfuric acid solution to vanadium slag powder, and leaching was carried out with continuous stirring for 3 hours. After the reaction was complete, the mixture was vacuum filtered, and the residue was washed three times with deionized water. The filtrate was collected and subjected to ICP analysis; the vanadium leaching rate was 55.05%.

[0043] III. The experimental conditions and parameters of Examples 1-9 and Comparative Examples 1-3 are shown in Table 2.

[0044]

[0045] As shown in Table 2, in Examples 1-3, the leaching agents prepared by mixing sulfuric acid and hydrogen peroxide achieved a vanadium dissolution rate of over 94% at 90°C, and no sulfur-containing substances were detected in the residue. In contrast, Comparative Example 1, using only sulfuric acid as the leaching agent, achieved a vanadium dissolution rate of only 55.05%.

[0046] Examples 4 and 5 show that the leaching agent prepared by mixing sulfuric acid and hydrogen peroxide can achieve a vanadium dissolution rate of over 80% under conditions of 70-80°C.

[0047] Examples 6-9 show that the vanadium leaching rate can reach over 90% when using a mixed leaching agent prepared with sulfuric acid, ClO2, sodium persulfate, sodium hypochlorite, or sodium chlorite at 90°C.

[0048] The liquid-to-solid ratio and leaching time can be adjusted according to the leaching agent and temperature conditions.

[0049] In contrast, in Comparative Examples 2 and 3, which used sulfuric acid as the leaching agent, the vanadium leaching rate was only 70.21%, even after adjusting the temperature or other parameters.

[0050] The principle of this invention is as follows: the vanadium-containing spinel phase in vanadium slag is often encapsulated by a silicate phase. Both phases exhibit high stability in sulfuric acid, making direct dissociation and leaching difficult. Given that vanadium and iron exist in low valence states in the slag, a strong oxidizing agent is introduced to oxidize and destroy the silicate phase structure and promote the dissociation of the vanadium-containing spinel phase. This simple and efficient oxidative acid leaching method simultaneously destroys the silicate-encapsulated phase and selectively dissociates the vanadium spinel phase in the vanadium slag, allowing the vanadium-containing phase to be fully exposed and rapidly dissolved, thus achieving highly efficient vanadium leaching.

[0051] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for direct oxidative acid leaching of vanadium from vanadium slag, characterized in that, Includes the following steps: The vanadium slag is crushed, ground, and then sieved to obtain fine vanadium slag particles smaller than 200 mesh. A mixed leaching agent solution is prepared by mixing sulfuric acid and oxidant solution in a certain proportion and stirring evenly. Under heating and stirring conditions, a mixed leaching agent is added to the fine vanadium slag to carry out a leaching reaction. After the reaction is completed, solid-liquid separation is performed to obtain a vanadium-containing leachate.

2. The method for direct oxidative acid leaching of vanadium from vanadium slag according to claim 1, characterized in that, In step a, the main phases of the vanadium slag are spinel, olivine and / or pyroxene.

3. The method for direct oxidative acid leaching of vanadium from vanadium slag according to claim 1, characterized in that, In step b, the sulfuric acid concentration in the leaching agent solution is 3-5 mol / L and the oxidant concentration is 0.6-1.0 mol / L. The mixed leaching agent solution is prepared according to a sulfuric acid to oxidant molar ratio of 3:1-5:0.

8.

4. The method for direct oxidative acid leaching of vanadium from vanadium slag according to claim 1, characterized in that, In step c, the mixed leaching agent is added to the vanadium slag at a liquid-solid ratio of 4:1 to 10:1 between the sulfuric acid-oxidant mixed leaching agent solution and the vanadium slag powder. The leaching temperature is 30 to 90°C, the leaching time is 0.5 to 3 hours, and after leaching, a vacuum filtration device is used to separate the solid and liquid to obtain a vanadium-containing leachate.

5. The method for direct oxidative acid leaching of vanadium from vanadium slag according to claim 1 or 3, characterized in that, The oxidant is selected from any one of hydrogen peroxide, ClO2, sodium persulfate, sodium hypochlorite, and sodium chlorite.

6. The method for direct oxidative acid leaching of vanadium from vanadium slag according to claim 4, characterized in that, In step c, the mixed leaching agent is added to the vanadium slag at a liquid-solid ratio of 6:1 to 10:1 between the sulfuric acid-oxidant mixed leaching agent solution and the vanadium slag powder. The leaching temperature is 70 to 90°C and the leaching time is 1.5 to 3 hours. After leaching, a vacuum filtration device is used to separate the solid and liquid to obtain a vanadium-containing leachate.

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