In the existing technology, using waste tungsten oxide (WO3) as a raw material, only low value-added ammonium paratungstate (APT) can be obtained, and high value-added ammonium metatungstate (AMT) products cannot be obtained. Moreover, WO3 waste ammonia after leaching, APT is needed to crystallize, so a crystallization reactor is necessary, and the investment in crystallization reactor equipment is relatively large, resulting in higher production costs and poor economic benefits, and the recovery rate of WO3 waste is low. Therefore, it is important to develop a method for producing AMT from WO3 waste with low equipment investment, low production cost, and high raw material recovery rate.
A method for preparing AMT with WO3 waste as a raw material is characterized in that it includes three main steps: ammonia leaching step, ammonium tungstate solution conversion step to dilute AMT solution, and dilute AMT solution concentration spray drying. The WO3 waste is directly implemented after ammonia leaching. The acid leaching step, after concentration, is directly spray-dried to obtain the AMT product.
The leaching step of WO3 waste material specifically includes: slowly adding the tungsten oxide waste material into the agitated ammonia water, while slowly flushing into the liquid ammonia, and controlling the free ammonia to 50-60g/L. The precautions for this process are as follows: when the WO3 content of the solution reaches 160-200g/L, boil and stir for more than 20 minutes, keep the temperature for at least 2 hours, let stand, filter, and obtain AMP; stand for 8-14 hours, let stand still The time selection is from the day before get off work to work the next day, which is the so-called overnight stay.
The precautions for the process of converting ammonium tungstate solution into ammonium metatungstate solution are as follows: pump the obtained ammonium tungstate solution into the reaction kettle and heat it to boiling, adjust the solution to a pH value of 4-5 with 1:4 nitric acid, when the solution content of WO3 is less than 30g/L, keep it for at least 2 hours, let stand for 3-5 hours, siphon the supernatant, slowly adjust the solution to pH 4-5 with 1:4 nitric acid, and then let it dissolve and stand still 2. Filter to obtain dilute ammonium metatungstate solution; concentrate and spray dry dilute AMT solution to prepare AMT powder product.
