CN104495927A - Method for preparing vanadium pentoxide - Google Patents

Abstract

The invention relates to a method for preparing vanadium pentoxide, and belongs to the field of wet-process metallurgy. The invention aims to solve the technical problem of providing the method for preparing vanadium pentoxide. The method provided by the invention comprises the following steps: re-dissolving ammonium poly-vanadate to remove ammonia gas, then adjusting the pH value to be 10-13, and performing sedimentation to remove impurities; performing ethanol crystallization to separate out a sodium poly-vanadate solid; re-dissolving the sodium poly-vanadate solid, and then depositing ammonium metavanadate; and baking to obtain vanadium pentoxide with the purity of 99.9%. Compared with the prior art, the method provided by the invention is simple in process, convenient to operate and low in requirement on equipment; the obtained vanadium pentoxide is high in purity and wide in application range; the ammonia gas can be recycled, ethanol can be recycled after rectification, the material loss is less, and the cost is saved; and waste liquid is applied to the process of depositing the ammonium poly-vanadate in a vanadium factory, so that the recycling of wastes is realized, pollution is reduced, and the environmental protection and comprehensive utilization of waste resources are promoted.

Description

The method for preparing vanadium pentoxide

technical field

The invention relates to a method for preparing vanadium pentoxide, belonging to the field of hydrometallurgy.

Background technique

High-purity vanadium pentoxide (that is, vanadium pentoxide with a purity of 99.9% and above) is mainly used in the field of high-end vanadium products, and is often used to prepare vanadium-containing catalysts, medical vanadyl sulfate, electrolytes for vanadium batteries, and metal vanadium products In terms of other aspects, the current demand is not very large, and the annual domestic demand is about 2,000 tons, but the price is expensive, the added value is high, and there is a prospect of a large number of applications.

At present, there are four main methods for preparing vanadium pentoxide with a purity of 99.9%. The first method is to obtain a vanadium-containing solution obtained by extracting vanadium from stone coal through multiple extraction operations to obtain a highly pure vanadium-containing solution. Post-roasting to obtain vanadium pentoxide; the second method is to extract the vanadium-containing catalyst and remove impurities by resin adsorption, deposit vanadium to obtain ammonium metavanadate with high purity, and obtain vanadium pentoxide after roasting. The vanadium pentoxide with a purity of more than 99.9% currently available on the market mainly comes from the products produced by the above two methods. However, the above two methods all have the defects of high impurity silicon content in the product, and the first method also has defects such as a large number of repeated operations and a long process route, and the second method also has the defects of few sources of raw materials and low yield.

The third method is that the vanadium-containing solution extracted from vanadium-titanium magnetite is removed by chemical reagents to remove impurities such as silicon and calcium, and then undergoes more than three times of repeated remelting and vanadium precipitation operations to obtain ammonium metavanadate with extremely high purity, which is obtained after roasting. Vanadium pentoxide. The method has defects such as many times of operation, long process route, low yield and high cost.

The fourth method is to redissolve ammonium polyvanadate with alkali, adjust the pH value to remove silicon, acidolyze and precipitate vanadium to obtain hydrolyzed red vanadium, then redissolve with alkali, precipitate ammonium metavanadate, and obtain vanadium pentoxide after roasting. This method removes impurities thoroughly but requires high equipment and inconvenient process operation.

Patent CN102730757A discloses a method for preparing high-purity vanadium pentoxide with ammonium metavanadate. In this method, the crude ammonium metavanadate is heated and dissolved in water, and after the dissolution, the pH value is adjusted to 8-10 with alkali, and then impurities are removed. After filtering, sodium metavanadate solution is obtained. Add ammonia water or ammonium salt to precipitate ammonium metavanadate to obtain ammonium metavanadate precipitate. After dehydration, the ammonium metavanadate precipitate is washed with dilute ammonium salt solution. After dehydration and roasting, high-purity vanadium pentoxide is obtained. This method requires an external impurity remover to remove impurities, the operation is complicated, the cost is high and the product has high impurity content.

Contents of the invention

The technical problem solved by the invention is to provide a method for preparing vanadium pentoxide.

The present invention prepares the method for vanadium pentoxide, comprises the steps:

a, react ammonium polyvanadate and sodium hydroxide solution, obtain reaction solution A, wherein, reaction temperature is 80～100 ℃, reaction time is more than 2h, and the pH value of reaction solution A after reaction finishes is 10.0～13.0;

b, the reaction solution A is left to stand, take the supernatant liquid, add ethanol to the supernatant liquid, by volume ethanol: supernatant liquid=1:1～1:5, let stand for 30～60min, filter, and get after washing Sodium polyvanadate solid;

c. Dissolve the sodium polyvanadate solid obtained in step b in high-purity water to obtain a vanadium-containing solution, add ammonium salt, in molar ratio, NH ₄ ⁺ :V=2.3～4.5:1, and stir at a temperature of 45～65°C Precipitate vanadium for 0.5-2h, let stand to cool, filter, and get ammonium metavanadate solid after washing;

d. Treating the ammonium metavanadate solid to obtain vanadium pentoxide.

Wherein, the concentration of the sodium hydroxide solution in step a is 60-80 g/L.

Wherein, the ammonia gas produced by the reaction of ammonium polyvanadate and sodium hydroxide solution in step a is absorbed by sulfuric acid solution to prepare ammonium sulfate solution for recovery, and is used to precipitate ammonium polyvanadate or ammonium metavanadate after recovery.

Wherein, in step b, the reaction solution A is left to stand for 30-40 hours, and the supernatant liquid is taken; in step b, the ethanol solution with a volume concentration of 30-80% is used for washing three times.

Wherein, the filtrate filtered and washed in step b is separated by distillation, and the isolated ethanol is returned to use in step b, and the remaining waste liquid of distillation is used to precipitate ammonium polyvanadate.

Wherein, the vanadium concentration of the vanadium-containing solution in step c is 30-130 g/L, preferably 40-70 g/L; the washing in step c is washed three times with saturated ammonium bicarbonate solution.

Wherein, the filtration in step b and step c is suction filtration.

Wherein, the step of treating the ammonium metavanadate solid described in step d is: drying the ammonium metavanadate solid obtained in step c, crushing and roasting at 500-550°C for 1.5-2.5h to obtain vanadium pentoxide .

In the present invention, ammonium polyvanadate is remelted to remove ammonia, and then the pH value is adjusted to between 10 and 13 to settle and remove impurities. Sodium polyvanadate solid is crystallized with ethanol, and ammonium metavanadate is precipitated after remelting the sodium polyvanadate solid. Calcined to obtain vanadium pentoxide with a purity of 99.9%. Compared with the prior art, the present invention has the following advantages:

1) The process is simple, the operation is convenient, and the requirements for equipment are not high;

2) the vanadium pentoxide that the present invention obtains has high purity and wide application range;

3) Recycling of ammonia gas, recycling of ethanol through rectification, less material loss and cost saving;

4) The waste liquid is put into the process of sinking ammonium polyvanadate in the vanadium plant, which realizes waste recycling, reduces pollution, and promotes environmental protection and comprehensive utilization of waste resources.

Detailed ways

The present invention prepares the method for vanadium pentoxide, comprises the steps:

A, ammonium polyvanadate and sodium hydroxide solution are reacted, obtain reaction solution A, wherein, reaction temperature is 80～100 ℃, and the reaction time is more than 2h, and the pH value of reaction solution A after reaction finishes is 10.0～13.0; When ammonium polyvanadate reacts with sodium hydroxide, ammonia gas will be produced. In order to make ammonium polyvanadate fully react, the amount of sodium hydroxide should be slightly excessive. After the reaction, the pH value of the reaction solution A can be controlled. The amount of addition, to ensure that the pH of the reaction solution A is 10.0 to 13.0 is more conducive to sedimentation and removal of impurities.

B, the reaction solution A is left standstill, get the supernatant liquid, add ethanol in the supernatant liquid, by volume ratio, ethanol: supernatant liquid=1:1～5, leave standstill more than 30min, filter, there is more vanadium after washing Sodium polyvanadate solid; and sodium polyvanadate solid is insoluble in ethanol, therefore, ethanol can be used to precipitate sodium polyvanadate solid.

c. Dissolve the sodium polyvanadate solid obtained in step b in high-purity water to obtain a vanadium-containing solution, add ammonium salt, in molar ratio, NH ₄ ⁺ :V=2.3～4.5:1, and stir at a temperature of 45～65°C Precipitate vanadium for 0.5-2 hours, filter after standing for cooling, and obtain ammonium metavanadate solid after washing; the high-purity water is water with extremely high chemical purity, and the content of impurities in it is less than 0.1mg/L. The purpose of using high-purity water is to maximize Avoid introducing impurities to obtain high-purity ammonium metavanadate.

d. Treat the ammonium metavanadate solid to obtain high-purity vanadium pentoxide.

The raw material ammonium polyvanadate of the present invention is crude ammonium polyvanadate with a purity of 95%-98% and contains various impurities such as silicon, calcium, chromium, magnesium and iron.

In the method for preparing vanadium pentoxide of the present invention, the sodium polyvanadate in the reaction solution A is soluble in water, but the impurities are insoluble in water, and the reaction solution A will be layered after standing, and the supernatant liquid is taken for subsequent operations, which can remove Impurities in reaction solution A. In order to ensure sufficient sedimentation and removal of impurities, the concentration of the sodium hydroxide solution in step a is preferably 60-80 g/L. In step b, the reaction solution A is left to stand for more than 30 hours, and the supernatant liquid is taken. In order to save time and improve efficiency, it is preferred that the reaction solution A be left to stand for 30-40 hours.

Further, in order to increase the yield of sodium polyvanadate solid, thereby increasing the yield of vanadium pentoxide, the washing in step b is preferably washed three times with an ethanol solution with a volume concentration of 30-80%.

Further, in order to improve the purity and yield of vanadium pentoxide, the vanadium concentration of the vanadium-containing solution in step c is 30-130 g/L, preferably 40-70 g/L; the washing in step c uses saturated ammonium bicarbonate solution Wash 3 times.

Further, in order to reduce costs and improve material utilization, the ammonia gas produced by the reaction of ammonium polyvanadate and sodium hydroxide solution in step a is absorbed by high-concentration sulfuric acid solution to prepare ammonium sulfate solution for recovery, and is used to precipitate polyvanadate after recovery. ammonium or ammonium metavanadate. In order to improve absorption efficiency, the sulfuric acid solution is preferably a sulfuric acid solution with a mass concentration of 70% or more.

The filtrate filtered and washed in the step b is separated by rectifying tower distillation, and the ethanol separated is returned to the step b for repeated use, and the remaining waste liquid of the distillation is returned to the operation of sinking ammonium polyvanadate in the vanadium plant to precipitate ammonium polyvanadate, Reduce pollution and promote environmental protection.

Ammonium salts commonly used in the art are applicable to the present invention, such as ammonium chloride, ammonium sulfate, ammonium bisulfate, ammonium nitrate, ammonium carbonate, ammonium bicarbonate and the like. In order to improve the purity of vanadium pentoxide, the ammonium salt in step c is preferably ammonium sulfate.

In order to simplify the operation and improve the filtering effect, the filtering in step b and step c is suction filtering.

Wherein, the step of treating the ammonium metavanadate solid described in step d is: drying the ammonium metavanadate solid obtained in step c, crushing and roasting at 500-550°C for more than 1.5h to obtain high-purity di vanadium. In order to save time and improve efficiency, the roasting time is preferably 1.5-2.5 hours.

The specific implementation of the present invention will be further described below in conjunction with the examples, and the present invention is not limited to the scope of the examples.

Example 1

Add 300g of ammonium polyvanadate to 3L of 60g/L sodium hydroxide solution, heat to maintain the reaction temperature at about 85°C and stir for 2 hours. At this time, the pH value of the solution after the reaction is 10.67; the solution after the reaction is allowed to stand 30h, pour out the supernatant, add 1L of ethanol to the supernatant while stirring, let it stand for 30min, filter with suction, wash the filter cake three times with 300ml of 30% ethanol solution and drain it; Sodium acid filter cake was dissolved in 1L of high-purity water to obtain a vanadium-containing solution with a vanadium concentration of 67.2g/L. Add 200g of ammonium sulfate and stir slowly at about 65°C for 2 hours to precipitate ammonium metavanadate. After standing and cooling, suction filter, and use 300ml The saturated ammonium bicarbonate solution was washed for 3 times, drained to obtain high-purity ammonium metavanadate solid; the ammonium metavanadate solid was dried, ground and pulverized, and roasted at 500°C for 1.5 hours to obtain high-purity ammonium pentoxide Two vanadium. The ammonia gas produced in the process is sent to the high-concentration sulfuric acid absorption pool through the exhaust equipment to absorb and prepare high-concentration ammonium sulfate solution, which is used to precipitate ammonium polyvanadate or ammonium metavanadate; The distilled ethanol can be used repeatedly, and the waste liquid left by rectification is returned to the process of sinking ammonium polyvanadate in the vanadium plant to sink ammonium polyvanadate.

Example 2

Add 300g of ammonium polyvanadate to 3L of 70g/L sodium hydroxide solution, heat and maintain the reaction temperature at about 90°C and stir for 2.5h. At this time, the pH value of the solution after the reaction is 11.35; Set aside for 35 hours, pour out the supernatant, add 1.5L of ethanol to the supernatant while stirring, let it stand for 45min, filter with suction, wash the filter cake three times with 400ml of 50% ethanol solution and drain it; Sodium polyvanadate filter cake was dissolved in 1.5L of high-purity water to obtain a vanadium-containing solution with a vanadium concentration of 49.3g/L. Add 300g of ammonium sulfate and stir slowly at about 50°C for 1.5h to precipitate ammonium metavanadate. Filter, wash with 400ml saturated ammonium bicarbonate solution for 3 times, and drain to obtain high-purity ammonium metavanadate solid; dry ammonium metavanadate solid, grind and pulverize, and roast at 520°C for 2 hours to obtain high-purity ammonium metavanadate solid Pure vanadium pentoxide. The ammonia gas produced in the process is sent to the high-concentration sulfuric acid absorption pool through the exhaust equipment to absorb and prepare high-concentration ammonium sulfate solution, which is used to precipitate ammonium polyvanadate or ammonium metavanadate; The distilled ethanol can be used repeatedly, and the waste liquid left by rectification is returned to the process of sinking ammonium polyvanadate in the vanadium plant to sink ammonium polyvanadate.

Example 3

Add 300g of ammonium polyvanadate to 3L of 80g/L sodium hydroxide solution, heat to maintain the reaction temperature at about 95°C and stir for 3 hours. At this time, the pH of the solution after the reaction is 11.82; the solution after the reaction is allowed to stand 40h, pour out the supernatant, add 2L of ethanol to the supernatant while stirring, let it stand for 60min, filter with suction, wash the filter cake three times with 500ml of 80% ethanol solution and drain it; Sodium acid filter cake was dissolved in 2L of high-purity water to obtain a vanadium-containing solution with a vanadium concentration of 40.7g/L. Add 400g of ammonium sulfate and stir slowly at about 45°C for 1h to precipitate ammonium metavanadate. The saturated ammonium bicarbonate solution was washed for 3 times, drained to obtain high-purity ammonium metavanadate solid; the ammonium metavanadate solid was dried, ground and pulverized, and roasted at 540°C for 2.5 hours to obtain high-purity ammonium pentoxide Two vanadium. The ammonia gas produced in the process is sent to the high-concentration sulfuric acid absorption pool through the exhaust equipment to absorb and prepare high-concentration ammonium sulfate solution, which is used to precipitate ammonium polyvanadate or ammonium metavanadate; The distilled ethanol can be used repeatedly, and the waste liquid left by rectification is returned to the process of sinking ammonium polyvanadate in the vanadium plant to sink ammonium polyvanadate.

Test example 1

The content of Na was measured by atomic absorption spectrometry, and the content of vanadium and other impurities in the prepared vanadium pentoxide was measured by ICP. The results are shown in Table 1, and the chemical composition in Table 1 is weight percent.

Table 1

To sum up, the method for preparing vanadium pentoxide of the present invention can effectively remove impurities in vanadium pentoxide, so that the purity of vanadium pentoxide can reach more than 99.9%, and its metal impurity content is low.

Claims (8)

1. prepare the method for vanadium pentoxide, it is characterized in that comprising the steps: a, react ammonium polyvanadate and sodium hydroxide solution, obtain reaction solution A, wherein, reaction temperature is 80～100 ℃, reaction time is more than 2h, and the pH value of reaction solution A after reaction finishes is 10.0～13.0; b, the reaction solution A is left to stand, take the supernatant liquid, add ethanol to the supernatant liquid, by volume ethanol: supernatant liquid=1:1～1:5, let stand for 30～60min, filter, and get after washing Sodium polyvanadate solid; c. Dissolve the sodium polyvanadate solid obtained in step b in high-purity water to obtain a vanadium-containing solution, add ammonium salt, in molar ratio, NH ₄ ⁺ :V=2.3～4.5:1, and stir at a temperature of 45～65°C Precipitate vanadium for 0.5-2 hours, let stand to cool, filter, and get ammonium metavanadate solid after washing; d. Treating the ammonium metavanadate solid to obtain vanadium pentoxide. 2. The method for preparing vanadium pentoxide according to claim 1, characterized in that: the concentration of the sodium hydroxide solution in step a is 60-80 g/L. 3. according to the method for claim 1 and 2 described preparation vanadium pentoxides, it is characterized in that: ammonium polyvanadate and sodium hydroxide solution react the ammonia gas that produces in the step a through sulfuric acid solution absorption and be prepared into ammonium sulfate solution recovery , After recovery, it is used to precipitate ammonium polyvanadate or ammonium metavanadate. 4. according to the method for preparing vanadium pentoxide described in any one of claim 1～3, it is characterized in that: in step b, reaction solution A is left standstill 30～40h, gets supernatant liquid; Washing in step b adopts volume Wash with 30-80% ethanol solution for 3 times. 5. according to the method for preparing vanadium pentoxide described in any one of claim 1～4, it is characterized in that: the filtrate that filters and washs in the step b is separated through distillation, and the ethanol that isolates returns to use in the step b, and the distillation residue The waste liquid below is used to precipitate ammonium polyvanadate. 6. The method for preparing vanadium pentoxide according to any one of claims 1 to 5, characterized in that: the vanadium concentration of the vanadium-containing solution in step c is 30 to 130 g/L, preferably 40 to 70 g/L; The washing in step c was washed 3 times with saturated ammonium bicarbonate solution. 7. The method for preparing vanadium pentoxide according to any one of claims 1 to 6, characterized in that: the filtration in step b and step c is suction filtration. 8. The method for preparing vanadium pentoxide according to any one of claims 1 to 7, characterized in that: the step of processing the ammonium metavanadate solid described in step d is: the ammonium metavanadate solid obtained by step c Drying, crushing, and roasting at 500-550°C for 1.5-2.5 hours to obtain vanadium pentoxide.