Ammonium Paratungstate from Fine Tungsten Slime

Fine tungsten slime refers to materials content tungsten hard to recover by re-election method in selecting tungsten concentrate, which the particle diameter is 0.074mm.   There are three kinds of technical methods for preparing ammonium paratungstate (APT) by using fine tungsten slime as following: classical, alkali extraction-ion exchange and alkali-extraction method.

Processing of low grade wolfram disposed with classical method is like below: alkaline leaching→ sodium tungstate solution crystallization→ P, As, Si removal→ molybdenum removal→ hydrochloric acid decomposition→ dissolution with ammonia→ ammonium paratungstate crystallization. The advantages of classical method are mature technology, simple equipment, easy to operate. However, the shortages are longer process, strict requirements of impurity content in material; besides, two specialized processes for impurities removal are needed.

A new process for preparing APT from fine tungsten slime is based in the classic method, and using appropriate technical measure, controlling the right conditions, simplify removing impurity process, save two steps in the classical method. Concrete steps are as following: alkali leaching→ sodium tungstate crystallization→ stirring and lye→ decomposition with hydrochloric acid→ ammonia solution dissolution with ammonia→ ammonium paratungstate crystallization→ stirring and washing in NH₄Cl solution.


The advantages of this method are as follows:
1. Solve the problems separated W and impurities like Mo, P, Si, As effectively, do not need a special purification process, so as to shorten the process, less equipment investment, reducing production costs, and with significant economic benefits;
2. Tungsten smelting total recovery rate can reach 90% or more, and APT with high purity and grain that can be controlled can be directly prepared reference to WO3GB3457-82;
3. The scale of production is not limited, can be large or small, strong adaptability to raw materials;
4. Simple equipment, extensive auxiliary material source, easy to operate;
5. To the environmental benefits, less displacement of waste gas, water and solid, and meeting industrial emission standards only simple handling.

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