What is tungstic acid?
The general formula of tungstic acid is mWO3•nH2O, the known tungstic acid is variety, and most of them are compounds which formed by the combination of tungsten trioxide WO3 and then united with water at different ratio and formation. Tungstic acid includes yellow, white tungstic acid and metatungstic acid ect..
Tungsten chloride hydrolysis method preparing tungsten acid has been researched for a long time, and with the developing of comprehensive utilization of low grade tungsten ore and recycling of waste tungsten material, it has been further promoted and applied. When tungsten or tungsten compounds reacts with chlorinating agent, it will generate the volatile tungsten compounds of oxychlorination tungsten (WOCl4, b.P.227℃), tungsten hexachloride (WCl6, b.P.346℃) and tungsten dichloride (WO2CI2,b.p.246℃) which are easily generating tungstic acid after hydrolysis, while the purity is as high as more than 99.9%; at present, the often used chlorinating agents are Cl2, HCl, CCl4, S2Cl2, SCl2 ect., and the chlorination efficiency is difference with the changing of chlorinating agents and reaction condition. However, since the harsh conditions of high toxicity of chlorinating agents and the temperature (Required among 500~1000℃), it will cause serious corrosion to the equipments, thus this method is still not widely promoted in industrial; but this process is widely used in vapor deposition to prepare tungsten composite materials, it can be predicted that this method is a promising new method for recycling waste tungsten.