Ammonium Paratungstate Preparation -- Evaporation Crystallization
Evaporation crystallization method is the most commonly used method of preparation of ammonium paratungstate , this method of technology and equipment is simple, easy to large-scale, have a certain role in the purification at the same time,it has been favored by industrial production. When the ammonium tungstate solution heated, the ammonia concentration decreased, (NH 4 ) 2WO 4 solution concentration gradually increased, ammonium paratungstate crystallization, the reaction is: 12(NH 4 )2WO 4 ==5(NH 4 )2O·12WO 3 ·5H 2 O+14NH 3 ↑+2H 2 O In industrial production, the degree of evaporation crystallization is generally based on the amount of molybdenum allowed in the solution and the product. There are usually two ways of batch intermittent operation and continuous crystal operation. The batch intermittent operation was carried out in a jacketed heated stirred tank, and a solution of (NH 4 ) 2WO 4 having a density of 1.16-1.28 g / cm3 was added to the reactor an...