Ammonium Paratungstate Purifying Method

Tungsten is important strategic metal resource, ammonium paratungstate is significant tungsten chemical products. There is strict requirement for ammonium paratungstate purity. Impurity content requirement for APT-0 is potassium, sodium and sulfide content respectively lower than 0.001%, 0.001%, 0.0008%. 

Especially with development of industry, traditional APT-0 can no longer satisfy requirement for high end tungsten product. So it is important to lower potassium, sodium, sulfide and chloride content.

Traditional method to remove these impurities is firstly dissolve APT in ammonia under 120~160℃, then remove impurity by recrystallization. Or use water or ammonia salt to wash APT product. However, the recycling rate of above is not high, the process is complex, cost high power and lots of water, results in environmental pollution.

Regarding the existing deficient technique, below method is brought up to remove potassium, sodium, sulfide and chloride in APT.

1)Mix 50g ammonium paratungstate with 280ml organic phase(15% N235, 15% octanol, 70% sulfonated kerosene), then stirring for 10 mins under 25℃ with 45ml nitride acid of concentration 3 mol/L. Dissolvent rate of APT is 100%, organic phase and water phase carrying tungsten is obtained.

2)Separate organic phase and water phase from step1, organic phase id 280ml, water phase is 45ml. WO3, Na, K, Cl, S concentration in water phase are 0.98, 0.82, 0.12, 0.54, 0.86g/L. Na, K, Cl, S removing rate are: 92.55, 86.3, 96.5, 96.5%.

3)Take 150ml ammonia water with weight content 15% to mix with carried organic phase to wash tungsten, stirring for 30min under 30℃, obtained ammonium tungstate solution with WO3, Na, K, Cl, S concentration respectively are 293.373、0.020、0.005、0.006、0.009g/L.

4)Evaporating ammonium tungstate solution from step 3 to 40ml, APT is obtained, among which WO3, Na, K, Cl, S weight content is respectively 88.5%、0.0008%、 0.0005%、0.0006%、0.0007%.

Compared to existing technology, new method can decompose APT directly under room temperature without traditional ammonium dissolvent method, at the same time realize separation of tungsten, potassium, sodium, sulphide, chloride. Decomposition time of APT is 3~15min, it is time consuming with high recycling rate of tungsten, has good separating effect, is easy to operate, can solve the deficiency of existing method.

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