What Factors Should be Paid Attention to in Producing High Purity APT
High purity quaternary ammonium paratungstate (APT) is a crystalline powder of ammonium paratungstate with a purity of 99.999% to 99.9999%. At present, the methods of producing high purity APT by controlling impurity content in industrial production are: re dissolution method, ion exchange method, ammonium tungstate method, electrolysis method, recrystallization method, etc.. But because of the different chemical properties of impurity elements, using only one method to achieve the purpose of removing all impurities, so the preparation of high purity APT often need two times of ion exchange, activated carbon adsorption and other means of further purification. It is found that the following three problems should be paid attention to during the purification of high purity ammonium paratungstate (APT). (1). The higher the crystallization rate, the higher the impurity content in APT crystallization. When the crystallization rate is more than 65%, the precipitation of impurities is accelera...