High Quality Ammonium Paratungstate Recycling from Waste Tungsten

Ammonium paratungstate is mainly used in the production of tungsten trioxide and tungsten powder, it can be further processed into tungsten strips, tungsten wires, tungsten carbide, alloy blades, alloy bits, alloy dies and other tungsten products, such as wear resistant, pressure resistant, and high temperature resistant mechanical components.

There are three main technologies for recycling and utilizing tungsten resources, including mechanical crushing, electrolysis and oxidation. In general, the tungsten products produced by the tungsten alloy recycling waste have the disadvantages of poor quality and low pollution emission. Therefore, some scholars have proposed a new method of high efficiency, low consumption, high recovery and environmental protection of the waste tungsten resources. The operation steps are as follows:

The 1.10 ton cemented carbide grinding waste (78% tungsten) is screened and broken, and the tungsten powder is made after ball milling for 1 hours. In the reaction container, 1m3 water is injected, acid is added, the acidity is adjusted to 70g/mL. The temperature of the acid solution is controlled at 70°C, and the impurities such as Co, Ni and Fe in the grinding material are removed.

Wet tungsten carbide slurry was obtained by solid liquid separation after acid leaching. After washing and blowing, the drying furnace was dried and dewater treated. The drying temperature was set to 250°C, the thickness of the material layer was 2.5cm. After drying, the tungsten oxide is oxidized into tungsten oxide by dry treatment in 700°C furnace.

In the ammonia solution of 150g/L, the prepared tungsten oxide was heated to 100°C, the transition pressure was controlled at 0.3MPa, and the crude tungstate solution was prepared after 7 hours of heat preservation. The trace impurity elements Co, Ni, Fe and Ca were converted into hydroxides and precipitated.

According to the residual impurities Cu, Al, Mg, Ti and other metal ions and S2^- content, the prepared crude tungstate solution was prepared by adding 10L ammonia and 50L hydrogen peroxide solution. The slag was precipitated for 6 hours. The solid solution was separated and the solution of tungsten tungstate was obtained. The soluble tungsten oxide content was 310g/L.

1.08 tons of ammonia tungstic acid A1 was prepared by evaporation crystallization and drying of ammonium tungstate solution. The performance of the product was APT-0 grade. It is estimated that the recovery rate of tungsten is up to 88%.

The ammonia gas produced in the process of evaporation and crystallization is converted directly into dilute ammonia water after the condensation water spray. The residual mother liquid after crystallization is completely crystallized and then reinvested in the acid leaching process, the production process has no wastewater discharge.

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