In the process of producing APT, about 10% ~ 15% of tungsten enters all kinds of slag washing water and APT crystallization mother liquor, the tungsten concentration of this solution is relatively low. The sediment filtrate and discharge waste water contains WO₃ about 0.1 ~ 2g/L, the exchange fluid discharged by the ion exchange contains about 0.1 ~ 0.5g/L of WO₃, and the mother liquor of evaporation crystallization contains WO₃ about 5 ~ 20g/L. The recovery and utilization of these tungsten containing wastewater is particularly important, and all tungsten smelting manufacturers attach great importance to it.

At present, there are two methods for the production of ammonium paratungstate. First, the industrial sodium tungstate solution is first made to make white tungsten, then the concentrated acid is made into tungstate under the condition of heating and cooking. Then tungstate is made into ammonium paratungstate. The industrial sodium tungstate solution through anion exchange resin and then rinse with concentrated ammonium chloride, so that tungsten is made into ammonium tungstate. Then, the tungsten is made into ammonium tungstate. It is evaporated into ammonium paratungstate. Both of two methods have no molybdenum removal. To achieve the purpose of removing molybdenum, or to reduce the crystallization rate of ammonium paratungstate to 70-80%, the mother liquid should be removed from molybdenum after reducing the crystallization rate.

At present, the recovery and processing of tungsten waste has become a large scale, forming industry, mainly using tungsten waste to treat the sodium tungstate with wet process. This method has a large amount of treatment and is widely used for the tungsten containing waste. However, this method has serious pollution to the environment and the process is more complex.

Selective catalytic reduction (SCR) technology and its key equipment denitration catalyst industry have been vigorously developed for the treatment of thermal power plants. Vanadium tungsten (molybdenum) titanium catalyst is the most widely used SCR denitration catalyst in SCR technology.