Ammonium Paratungstate Recycle from Tungsten Waste by Centrifugal Extraction

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 the recycle of waste products from tungsten, such as catalysts, waste alloys, the 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. The leaching solution obtained from the above two leaching methods is a mixture of sodium tungstate and sodium carbonate, which usually contains a small amount of impurities such as P, As, Si and so on. This solution is a soda leaching solution containing tungsten.

The traditional acid extraction method has the shortcomings of low recycle efficiency and high pollution. In order to overcome the shortcomings of acid extraction, some scholars have improved it. The improved process is short and the consumption of chemical reagents is small, which is good for environmental protection. The volume percentage concentration of the carbonates of the extractant methyl three alkyl ammonium in the organic phase is between 10% and 60%. The whole process of extraction and anti extraction were carried out in centrifugal extractor.

Compared with the current acid extraction method, the improved scheme has the following advantages: (1) The extraction of tungsten is directly carried out in alkaline medium, without consuming inorganic acid to neutralize the free alkali and acidity of the soda leaching solution of tungsten containing materials. (2) Separation of impurities P, As, Si and tungsten from tungsten can be realized at the same time of transformation (converting sodium tungstate solution into ammonium tungstate solution), eliminating the steps of removing P, As and Si by chemical precipitation; (3) The raffinate is sodium carbonate solution, which can be returned directly to the soda leaching of tungsten containing materials, and can form a closed cycle of water with the leaching process, which not only restores sodium carbonate, but also reduces wastewater discharge.

The problem of the difficulty of phase separation and the low concentration of WO₃ in the extraction solution in the alkaline extraction system can be effectively solved, so that the alkaline extraction method is easy to be industrialized.

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