CN-120757147-B - Method for removing chromium from sodium tungstate solution

Abstract

The application belongs to the technical field of tungsten hydrometallurgy, and particularly relates to a method for removing chromium from a sodium tungstate solution, which comprises the following steps of adjusting the pH value of the chromium-containing sodium tungstate solution to 9-12, heating to 80-90 ℃ and preserving heat to obtain a pretreated sodium tungstate solution, mixing ferrous salt and aluminum salt with the mass ratio of 3:1-4:1, adding a proper amount of water, stirring until the ferrous salt and the aluminum salt are dissolved to obtain a chromium removing reagent, adding the chromium removing reagent into the pretreated sodium tungstate solution, stirring, standing and filtering to obtain the chromium-removed sodium tungstate solution. The application adopts ferrous salt and aluminum salt to prepare solution, reduces the consumption of precipitant, thereby reducing the chromium removal cost, generates Al (OH) 3 by introducing aluminum salt to wrap the surface of formed Fe (OH) 3 colloid precipitate, reduces tungsten loss, has less sludge produced by the technical scheme, is simple to treat, improves the purity of sodium tungstate, improves the quality and performance of tungsten products, meets the production requirements of different scales, and has stronger adaptability.

Inventors

• ZHANG XIN
• XU GUOZUAN
• ZHANG LONGHUI
• HUANG QINGLAN
• ZHANG DAIBIN
• ZENG HUI
• FU YU

Assignees

• 崇义章源钨业股份有限公司

Dates

Publication Date

20260512

Application Date

20250908

Claims (4)

1. 1. A method for removing chromium from a sodium tungstate solution, comprising the steps of: S1, obtaining a sodium tungstate solution, wherein the sodium tungstate solution contains chromium elements, the content of the chromium elements in the sodium tungstate solution is 0.01-10 g/L, and the existence form of the chromium elements in the sodium tungstate solution comprises at least one of CrO 4 2－ 、Cr 2 O 7 2－ ; S2, mixing ferrous sulfate and aluminum sulfate, adding a proper amount of water, and stirring until the ferrous sulfate and the aluminum sulfate are dissolved to obtain a chromium removal reagent, wherein the molar ratio of ferrous ions in the chromium removal reagent to chromium elements in the sodium tungstate solution is 3.15:1-4.50:1, and the mass ratio of the ferrous sulfate to the aluminum sulfate is 3:1-4:1; S3, adding the chromium removing reagent into the pretreated sodium tungstate solution, stirring, standing, and filtering to obtain a chromium-removed sodium tungstate solution and precipitated slag; the content of chromium element in the sodium tungstate solution after chromium removal is less than 10mg/L, and the content of WO 3 in the precipitation slag is less than 1.5%.
2. 2. The method for removing chromium from a sodium tungstate solution according to claim 1, wherein in the step S1, the pH of the sodium tungstate solution is adjusted to 11-12 at normal temperature.
3. 3. The method for removing chromium from a sodium tungstate solution according to claim 1, wherein in the step S3, the stirring time is 1 to 2 hours.
4. 4. The method for removing chromium from a sodium tungstate solution according to claim 1, wherein in the step S3, the standing time is 1 to 2 hours.

Description

Method for removing chromium from sodium tungstate solution Technical Field The application belongs to the technical field of tungsten hydrometallurgy, and particularly relates to a method for removing chromium from a sodium tungstate solution. Background Sodium tungstate is an important tungsten compound and plays a key role in the production of tungsten materials. Aiming at the problems of long process flow, poor comprehensive utilization, poor applicability and the like of the traditional recycling treatment technology of the waste hard alloy, the novel process route for treating the waste hard alloy by an alkali fusion roasting-water leaching process is gradually accepted by various manufacturers, wherein the main component WC can be converted into soluble Na 2WO4 to be dissolved in a solution in one step, and components such as cobalt, copper, iron and the like exist in slag in the form of solid-phase slag to realize the selective separation of tungsten, and particularly, when the waste hard alloy blade is treated, the alkali fusion decomposition of the waste hard alloy blade can be realized in one step and high efficiency without pretreatment such as oxidative decomposition, physical crushing, ball milling and the like, and the coarse sodium tungstate solution and cobalt slag are respectively obtained by water leaching. However, in the production process of sodium tungstate, the purity and performance of tungsten products are seriously affected by the existence of chromium impurities, and meanwhile, environmental pollution and health risks are brought. Therefore, how to efficiently remove chromium impurities in sodium tungstate becomes an important challenge in the technical field of tungsten material production. Currently, in order to remove chromium impurities in sodium tungstate, methods mainly adopted include a chemical precipitation method, an ion exchange method, a membrane separation method and the like. These methods are capable of removing chromium impurities to some extent, but suffer from significant drawbacks. The chemical precipitation method generally needs to add a large amount of precipitant, so that the chromium removal cost is high, the generated sludge is complex to treat, the ion exchange method can remove chromium ions, but the exchange resin is difficult to regenerate, the treatment efficiency is low, the requirement of mass production is difficult to meet, the membrane separation method has the problems of membrane pollution and short membrane service life, and the maintenance cost is high, so that the method is limited in practical application. In CN114635041B, a sodium tungstate solution is dechromized by using a ferrous salt, a part of Fe 2+ reduces hexavalent chromium to trivalent chromium and forms Fe 3+,Fe3+ by hydrolysis to form Fe (OH) 3, a part of Fe 2+ is hydrolyzed to form Fe (OH) 2, oxygen in the solution or in the air oxidizes a part of Fe (OH) 2 to Fe (OH) 3, and finally forms an intermediate product Fe (OH) 2·2Fe(OH)3, which has adsorptivity, and trivalent chromium is hydrolyzed to Cr (OH) 3,Cr(OH)3 and forms coprecipitation with Fe (OH) 2·2Fe(OH)3, but the amount of ferrous salt added in the patent is too large, the generated Fe 3+ itself forms iron tungstate with tungstate ions in the sodium tungstate solution, and the precipitated ferrous hydroxide (iron) has adsorptivity to WO 3, resulting in a large tungsten loss. Patent CN106186064B proposes a method of co-precipitation, in which aluminum salt is added first, then ferrous salt is added, and chromium in ammonium metavanadate is reduced by means of ion precipitation, although the method can deeply remove chromium, the loss of main elements is neglected. The prior art can remove chromium impurities in sodium tungstate to a certain extent, but still has some problems and disadvantages. Therefore, a novel efficient chromium removal method is developed, and the method has important practical significance and application value. Disclosure of Invention Aiming at the problems, the application provides a method for removing chromium from a sodium tungstate solution, which is characterized in that ferrous salt and aluminum salt are mixed according to a certain proportion to prepare a chromium removing reagent, and under the specific pH condition, the chromium content is reduced and the tungsten loss is reduced through oxidation-reduction reaction and hydrolysis reaction, so that the recovery rate of sodium tungstate is improved. The application discloses a method for removing chromium from a sodium tungstate solution, which comprises the following steps: s1, obtaining a sodium tungstate solution, wherein the sodium tungstate solution contains chromium element, regulating the pH of the sodium tungstate solution to 9-12, then heating to 80-90 ℃ and preserving heat to obtain a pretreated sodium tungstate solution; S2, mixing ferrous salt and aluminum salt, adding a proper amount of water, and stirring until the ferrou