Method for preparing high-purity vanadium pentoxide based on nano-filtration and membrane separation coupling

Abstract

The invention discloses a method for preparing high-purity vanadium pentoxide based on nano-filtration and membrane separation coupling. The method comprises the following steps: (1) carrying out ball milling and sieving on vanadium slag; mixing the ball-milled vanadium slag with a sodium hydroxide solution, and removing insoluble impurities to obtain a vanadium-containing solution; (2) adding ethoxylated fatty acid methyl ester into the vanadium-containing solution, and uniformly stirring to obtain a vanadium-containing mixed solution; pressurizing to enable the vanadium-containing mixed solution to pass through a nanofiltration membrane, and collecting a vanadium-containing concentrated solution; (3) adding ammonium sulfate into the vanadium-containing concentrated solution, and stirring to separate out precipitate to obtain a vanadium-containing solid; and (4) drying and calcining the vanadium-containing solid to obtain vanadium pentoxide. The purity of the obtained vanadium pentoxide is greater than or equal to 99.99%, and the recovery rate of vanadium is greater than or equal to 95.0%. The method is simple in technological process, the vanadium-containing solution is purified through a nano-filtration and membrane separation method, the separation process is simple and convenient, the separation efficiency is high, the production period can be shortened, the cost is reduced, and environmental pollution is reduced.

Description

Technical Field

[0001] This invention belongs to the field of vanadium chemical metallurgy technology, specifically relating to a method for preparing high-purity vanadium pentoxide based on the coupling of nanofiltration and membrane separation. Background Technology

[0002] The traditional method for producing vanadium pentoxide is the sodium roasting of vanadium slag followed by ammonium salt precipitation, with over 65% of the vanadium product coming from this method. There are two types of ammonium salt precipitation: one involves adjusting the pH of the solution containing pentavalent vanadium to 8.5–9.5, then adding ammonium salt at a V₂O₅ to ammonium salt mass ratio of 1:1.3–1.5 to precipitate ammonium metavanadate; the other involves adjusting the pH of the solution stepwise to 1.5–2.5, adding ammonium salt to precipitate ammonium polyvanadate, and then calcining the obtained ammonium metavanadate or ammonium polyvanadate to obtain vanadium pentoxide. Because there is no suitable method to remove impurities introduced during the vanadium precipitation process in subsequent steps, the vanadium pentoxide obtained using these processes has a high impurity content, typically only around 98% purity, containing impurity elements such as Fe, Al, K, Na, Ca, Mg, Si, P, S, and As, making it difficult to meet the purity requirements of various fields. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a method for preparing high-purity vanadium pentoxide based on the coupling of nanofiltration and membrane separation. The process is relatively simple and the vanadium pentoxide obtained has high purity.

[0004] The technical solution adopted by this invention to solve its technical problem is a method for preparing high-purity vanadium pentoxide based on the coupling of nanofiltration and membrane separation, comprising the following steps: (1) Ball mill the vanadium slag and pass it through a 100-mesh sieve (to ensure that the contact area for dissolution is large enough, to speed up the dissolution rate and increase the recovery rate); mix the ball-milled vanadium slag with sodium hydroxide solution. After the vanadium slag is dissolved, control the final pH value of the solution to 8-9, filter, remove insoluble impurities, and obtain a vanadium-containing solution.

[0005] (2) Add ethoxylated fatty acid methyl ester to the vanadium-containing solution obtained in step (1), stir evenly to obtain a vanadium-containing mixture; add the obtained vanadium-containing mixture to a nanofiltration device, pressurize and pass the vanadium-containing mixture through the nanofiltration membrane, and collect the vanadium-containing concentrate. In this step, the vanadium-containing mixture is pressurized and passed through a nanofiltration membrane, allowing small molecules or ions of impurities to permeate and produce a high-purity vanadium-containing concentrate. Soluble small molecules or impurity ions are then removed from the vanadium-containing mixture using nanofiltration separation technology. The vanadium-containing mixture undergoes percolation at the nanofiltration membrane surface, separating into permeate and concentrate. The permeate is the filtrate containing the small molecules or ions of impurities. The concentrate is the vanadium-containing concentrate after the small molecules or ions of impurities have been removed. At the end of nanofiltration, the vanadium-containing concentrate is collected to obtain a high-purity vanadium-containing solution.

[0006] Studies have shown that ethoxylated fatty acid methyl esters can selectively retain more metavanadate ions, preventing them from passing through the nanofiltration membrane, while other small molecule soluble impurities can pass through the nanofiltration membrane, thereby improving the recovery rate and purity of vanadium.

[0007] (3) Add ammonium sulfate to the vanadium-containing concentrate obtained in step (2), stir to precipitate, and stop adding ammonium sulfate until no precipitate is produced. Separate the liquid and solid to obtain vanadium-containing solid. Wash the vanadium-containing solid with deionized water (to remove ethoxylated fatty acid methyl esters and other water-soluble impurities).

[0008] (4) Dry and calcine the vanadium-containing solid after washing in step (3) to obtain vanadium pentoxide.

[0009] Furthermore, in step (2), after adding ethoxylated fatty acid methyl ester, the mass concentration of ethoxylated fatty acid methyl ester in the solution is 0.1-0.2%. If the amount of ethoxylated fatty acid methyl ester is too small, the yield and purity of vanadium will decrease; if the amount is too large, the number of subsequent water washings will be more, but it will not help to improve the yield and purity.

[0010] Furthermore, in step (2), the pore size of the nanofiltration membrane is 1 to 2 nanometers.

[0011] Furthermore, in step (2), the temperature is maintained at 20–30°C during nanofiltration.

[0012] Furthermore, in step (2), the pressure difference of the pressurization is 0.02 to 2.00 MPa.

[0013] Furthermore, in step (2), the temperature of the liquid is 10℃~70℃.

[0014] Furthermore, in step (2), the membrane material of the nanofiltration membrane used is at least one of polysulfone (PS), polyacrylonitrile (PAN), polyvinylidene fluoride (PVDF), polyethersulfone (PES), polyamide (PA), cellulose acetate (CA), etc.

[0015] Furthermore, in step (2), the molecular weight cutoff of the nanofiltration membrane used is 100 to 1000 daltons.

[0016] The vanadium pentoxide obtained by this invention has a purity of ≥99.99% and a vanadium recovery rate of ≥95.0%.

[0017] This invention first filters out insoluble impurities of large molecules, then removes small molecule impurities by membrane separation, leaving sodium metavanadate as the residue.

[0018] The method of this invention can be used for the production of high-purity vanadium. The process is simple, using nanofiltration and membrane separation to purify vanadium-containing solutions. The separation process is simple, can be operated at room temperature, and has high separation efficiency. It can shorten the production cycle, reduce costs, reduce environmental pollution, and has high separation selectivity. It can achieve continuous and automated production, meeting the needs of modern production. Detailed Implementation

[0019] The present invention will be further described in detail below with reference to specific embodiments. Example 1

[0020] The method for preparing high-purity vanadium pentoxide based on the coupling of nanofiltration and membrane separation in this embodiment includes the following steps: (1) Ball mill the vanadium slag and pass it through a 100-mesh sieve (to ensure that the contact area for dissolution is large enough, to speed up the dissolution rate and increase the recovery rate); mix the ball-milled vanadium slag with sodium hydroxide solution. After the vanadium slag is dissolved, control the final pH value of the solution to 8, filter, remove insoluble impurities, and obtain a vanadium-containing solution.

[0021] (2) Add ethoxylated fatty acid methyl ester to the vanadium-containing solution obtained in step (1), stir evenly to obtain a vanadium-containing mixture; add the obtained vanadium-containing mixture to a nanofiltration device, pressurize and pass the vanadium-containing mixture through the nanofiltration membrane, and collect the vanadium-containing concentrate. In step (2), after adding ethoxylated fatty acid methyl ester, the mass concentration of ethoxylated fatty acid methyl ester in the solution is 0.1%. Too little ethoxylated fatty acid methyl ester will reduce the yield and purity of vanadium; too much will require more subsequent water washings, but will not significantly improve the yield and purity.

[0022] In step (2), the pore size of the nanofiltration membrane is 1 to 2 nanometers.

[0023] In step (2), the temperature is maintained at 20-30℃ during nanofiltration.

[0024] In step (2), the pressure difference is 0.2 MPa.

[0025] In step (2), the temperature of the liquid is 20°C.

[0026] In step (2), the membrane material of the nanofiltration membrane used is polysulfone (PS).

[0027] In step (2), the molecular weight cutoff of the nanofiltration membrane used is 100 to 1000 daltons.

[0028] (3) Add ammonium sulfate to the vanadium-containing concentrate obtained in step (2), stir to precipitate, and stop adding ammonium sulfate until no precipitate is produced. Separate the liquid and solid to obtain vanadium-containing solid. Wash the vanadium-containing solid with deionized water (to remove ethoxylated fatty acid methyl esters and other water-soluble impurities).

[0029] (4) Dry and calcine the vanadium-containing solid after washing in step (3) to obtain vanadium pentoxide.

[0030] The purity of vanadium pentoxide obtained by this invention is 99.995%, and the vanadium recovery rate is 96.8%. Example 2

[0031] The method for preparing high-purity vanadium pentoxide based on the coupling of nanofiltration and membrane separation in this embodiment includes the following steps: (1) Ball mill the vanadium slag and pass it through a 100-mesh sieve (to ensure that the contact area for dissolution is large enough, to speed up the dissolution rate and increase the recovery rate); mix the ball-milled vanadium slag with sodium hydroxide solution. After the vanadium slag is dissolved, control the final pH value of the solution to 9, filter, remove insoluble impurities, and obtain a vanadium-containing solution.

[0032] (2) Add ethoxylated fatty acid methyl ester to the vanadium-containing solution obtained in step (1), stir evenly to obtain a vanadium-containing mixture; add the obtained vanadium-containing mixture to a nanofiltration device, pressurize and pass the vanadium-containing mixture through the nanofiltration membrane, and collect the vanadium-containing concentrate. In step (2), after adding ethoxylated fatty acid methyl ester, the mass concentration of ethoxylated fatty acid methyl ester in the solution is 0.2%. Too little ethoxylated fatty acid methyl ester will reduce the yield and purity of vanadium; too much will require more subsequent water washings, but will not significantly improve the yield and purity.

[0033] In step (2), the pore size of the nanofiltration membrane is 1 to 2 nanometers.

[0034] In step (2), the temperature is maintained at 20-30℃ during nanofiltration.

[0035] In step (2), the pressure difference is 2.00 MPa.

[0036] In step (2), the temperature of the liquid is 30°C.

[0037] In step (2), the membrane material of the nanofiltration membrane used is polyacrylonitrile (PAN).

[0038] In step (2), the molecular weight cutoff of the nanofiltration membrane used is 100 to 1000 daltons.

[0039] (3) Add ammonium sulfate to the vanadium-containing concentrate obtained in step (2), stir to precipitate, and stop adding ammonium sulfate until no precipitate is produced. Separate the liquid and solid to obtain vanadium-containing solid. Wash the vanadium-containing solid with deionized water (to remove ethoxylated fatty acid methyl esters and other water-soluble impurities).

[0040] (4) Dry and calcine the vanadium-containing solid after washing in step (3) to obtain vanadium pentoxide.

[0041] The purity of vanadium pentoxide obtained by this invention is 99.993%, and the vanadium recovery rate is 96.0%. Example 3

[0042] The method for preparing high-purity vanadium pentoxide based on the coupling of nanofiltration and membrane separation in this embodiment includes the following steps: (1) Ball mill the vanadium slag and pass it through a 100-mesh sieve (to ensure that the contact area for dissolution is large enough, to speed up the dissolution rate and increase the recovery rate); mix the ball-milled vanadium slag with sodium hydroxide solution. After the vanadium slag is dissolved, control the final pH value of the solution to 9, filter, remove insoluble impurities, and obtain a vanadium-containing solution.

[0043] (2) Add ethoxylated fatty acid methyl ester to the vanadium-containing solution obtained in step (1), stir evenly to obtain a vanadium-containing mixture; add the obtained vanadium-containing mixture to a nanofiltration device, pressurize and pass the vanadium-containing mixture through the nanofiltration membrane, and collect the vanadium-containing concentrate. In step (2), after adding ethoxylated fatty acid methyl ester, the mass concentration of ethoxylated fatty acid methyl ester in the solution is 0.2%. Too little ethoxylated fatty acid methyl ester will reduce the yield and purity of vanadium; too much will require more subsequent water washings, but will not significantly improve the yield and purity.

[0044] In step (2), the pore size of the nanofiltration membrane is 1 to 2 nanometers.

[0045] In step (2), the temperature is maintained at 20-30℃ during nanofiltration.

[0046] In step (2), the pressure difference is 1.00 MPa.

[0047] In step (2), the temperature of the liquid is 50°C.

[0048] In step (2), the membrane material of the nanofiltration membrane used is polyvinylidene fluoride.

[0049] In step (2), the molecular weight cutoff of the nanofiltration membrane used is 100 to 1000 daltons.

[0050] (3) Add ammonium sulfate to the vanadium-containing concentrate obtained in step (2), stir to precipitate, and stop adding ammonium sulfate until no precipitate is produced. Separate the liquid and solid to obtain vanadium-containing solid. Wash the vanadium-containing solid with deionized water (to remove ethoxylated fatty acid methyl esters and other water-soluble impurities).

[0051] (4) Dry and calcine the vanadium-containing solid after washing in step (3) to obtain vanadium pentoxide.

[0052] The purity of vanadium pentoxide obtained by this invention is 99.992%, and the vanadium recovery rate is 95.8%.

[0053] Comparative Example 1 In this comparative example, except that ethoxylated fatty acid methyl esters were not added in step (2), all other operations and parameters were the same as in Example 1. The purity of vanadium pentoxide obtained in this comparative example was 98.25%, and the vanadium recovery rate was 95.2%.

[0054] Comparative Example 2 In this comparative example, except for the addition of ethoxylated fatty acid methyl ester in step (2) to achieve a mass concentration of ethoxylated fatty acid methyl ester in the solution of 0.05%, all other operations and parameters were the same as in Example 1. The purity of vanadium pentoxide obtained in this comparative example was 99.03%, and the vanadium recovery rate was 95.9%.

[0055] Comparative Example 3 In this comparative example, except for the addition of ethoxylated fatty acid methyl ester in step (2) to achieve a mass concentration of ethoxylated fatty acid methyl ester in the solution of 0.3%, all other operations and parameters were the same as in Example 1. The purity of vanadium pentoxide obtained in this comparative example was 99.994%, and the vanadium recovery rate was 94.3%.

Claims

1. A method for preparing high-purity vanadium pentoxide based on the coupling of nanofiltration and membrane separation, characterized in that, Includes the following steps: (1) Ball mill the vanadium slag and pass it through a 100-mesh sieve; mix the ball-milled vanadium slag with sodium hydroxide solution. After the vanadium slag dissolves, control the final pH value of the solution to 8-9, filter, remove insoluble impurities, and obtain a vanadium-containing solution. (2) Add ethoxylated fatty acid methyl ester to the vanadium-containing solution obtained in step (1), stir evenly to obtain a vanadium-containing mixture; add the obtained vanadium-containing mixture to a nanofiltration device, pressurize and pass the vanadium-containing mixture through the nanofiltration membrane, and collect the vanadium-containing concentrate. (3) Add ammonium sulfate to the vanadium-containing concentrate obtained in step (2), stir to precipitate, until no precipitate is produced, stop adding ammonium sulfate, separate the liquid and solid to obtain vanadium-containing solid; wash the vanadium-containing solid with deionized water; (4) Dry and calcine the vanadium-containing solid after washing in step (3) to obtain vanadium pentoxide.

2. The method for preparing high-purity vanadium pentoxide based on the coupling of nanofiltration and membrane separation according to claim 1, characterized in that, In step (2), after adding ethoxylated fatty acid methyl ester, the mass concentration of ethoxylated fatty acid methyl ester in the solution is 0.1-0.2%.

3. The method for preparing high-purity vanadium pentoxide based on the coupling of nanofiltration and membrane separation according to claim 1 or 2, characterized in that, In step (2), the pore size of the nanofiltration membrane is 1 to 2 nanometers.

4. The method for preparing high-purity vanadium pentoxide based on the coupling of nanofiltration and membrane separation according to claim 1 or 2, characterized in that, In step (2), the temperature is maintained at 20-30℃ during nanofiltration.

5. The method for preparing high-purity vanadium pentoxide based on the coupling of nanofiltration and membrane separation according to claim 1 or 2, characterized in that, In step (2), the pressure difference is 0.02 to 2.00 MPa.

6. The method for preparing high-purity vanadium pentoxide based on the coupling of nanofiltration and membrane separation according to claim 1 or 2, characterized in that, In step (2), the temperature of the liquid is 10℃~70℃.

7. The method for preparing high-purity vanadium pentoxide based on the coupling of nanofiltration and membrane separation according to claim 1 or 2, characterized in that, In step (2), the membrane material of the nanofiltration membrane is at least one of polysulfone (PS), polyacrylonitrile, polyvinylidene fluoride, polyethersulfone, polyamide, and cellulose acetate.

8. The method for preparing high-purity vanadium pentoxide based on the coupling of nanofiltration and membrane separation according to claim 1 or 2, characterized in that, In step (2), the molecular weight cutoff of the nanofiltration membrane used is 100 to 1000 daltons.