Tungsten is a very important non-ferrous metal. It has the properties of high density and high hardness. It is commonly used in counterweight materials, shielding materials and military materials. Tungsten-zirconium alloy has a broad application prospect in the military field due to its strong resistance to corrosion.

Nitrogen oxides (NOx) are recognized as one of the major sources of atmospheric pollution, including combustion fumes and automobile exhaust. Monolithic vanadium-titanium-based catalysts have been widely used for the removal of NOx from combustion fumes or automobile exhaust, and NOx is removed by selectively catalyzing the reduction of NOx by NH3 to N2. The catalyst uses TiO2 as a carrier (usually 80-90% of the total mass), V2O5 as an active component (1-2%), and WO3 as a co-catalyst (5-10%).

Heterojunctions have become an essential element of the modern semiconductor industry, and they play an important role in high-speed electronic devices and optoelectronic devices. Two-dimensional layered materials, including graphene and transition metal disulfide, can serve as a constituent unit of a heterostructure due to their unique electrical and optical properties.

At present, ammonium paratungstate can completely dissolve for 1~4 hours at a temperature of 120~160°C with high concentration of ammonia, some enterprises promote the decomposition of ammonium paratungstate and even through high temperature roasting to get tungsten oxide, then ammonium tungstate solution is dissolved in ammonia water, and some enterprises use sodium hydroxide and other strong alkali to dissolve ammonium paratungstate. The ammonium tungstate solution is regenerated from sodium tungstate solution, the process is complex and costly. Therefore, it is necessary to develop a new low-cost and simple dissolution process for ammonium paratungstate / tungsten trioxide.