Ammonium Paratungstate Acid Extraction from Tungsten Waste

Tungsten is an important rare metal element and has a wide range of uses in industry. There are two kinds of tungsten materials in industry, one is to extract tungsten from tungsten ore, which is called primary tungsten. The other is to recycle waste from tungsten products, such as catalysts, waste alloys and so on. This secondary resource called tungsten, tungsten resources become increasingly scarce, the proportion of secondary resources of tungsten is also growing.

Tungsten waste made of ammonium paratungstate generally need to used in the two process of soda leaching and solution extraction. An important method of preparing ammonium tungstate solution from soda leachate containing tungsten material is solvent extraction. Current industrial extraction method to weak alkaline polymer amines (such as polymer tertiary amines, primary amines, secondary amines, etc.) as an extractant in the acidic (pH 2 ~ 4) under the conditions of extraction of tungsten, loaded with organic phase ammonium tungstate solution obtained by stripping with ammonia solution is called acidic extraction method.

Taking tertiary amine as an example, the organic solvent extraction process has four stages: pretreatment and acidification, extraction, washing and stripping. The whole extraction process is carried out in a box mixer settler.

In the preprocessing stage, the extraction process, phosphorus, arsenic and silicon and tungsten slime will form heteropoly acid ions are extracted into organic phase, tertiary amine extraction process does not separate these impurities, affecting the extraction quality, so we should work before the start of extraction and purification, chemical precipitation method, general with hydrochloric acid removing silicon, tin, MgCl2 removal of phosphorus, arsenic and fluorine.

There are some disadvantages of acidic extraction: (1) The leachate containing a large amount of free sodium carbonate should be adjusted to acidic (pH 2 ~ 4) to waste both the free sodium carbonate in the leachate and the consumption of a large amount of inorganic acid (sulfuric acid or hydrochloric acid ), and inorganic salts produced by acid-base neutralization will also pollute the environment; (2) Since P, As and Si can form heteropolyacid with tungsten under acidic conditions, impurities such as P, As and Si will be extracted into the organic phase together with tungsten during the extraction process, so acidic extraction method does not have the exception of P, As, Si and other impurities but only the function of sodium tungstate solution into ammonium tungstate solution. Impurities P, As, Si, etc. need to be chemically precipitated (magnesium salt method or ammonium magnesium salt method) pre-removed in sodium tungstate solution, chemical reagents consumed and the process of tungsten loss.

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