The raw materials for the synthesis of polyaluminum chloride by the metal aluminum method are mainly leftovers from aluminum processing, such as aluminum scraps, aluminum ash, and aluminum slag. The aluminum ash is slowly added with hydrochloric acid in a certain proportion under stirring to react, and the liquid polyaluminum chloride is prepared by mature polymerization and sedimentation, and then is prepared by diluting, filtering, concentrating, and drying. In terms of technology, it can be divided into three types: acid method, alkali method, and neutralization method. The acid method mainly uses HCl, and the product quality is not easy to control; the alkaline production process is more difficult, the equipment investment is large, the amount of alkali used is large, the pH control costs raw materials, and the cost is high; the neutralization method is the most used, as long as the control is required Good ratio, generally can meet national standards.
Aluminum hydroxide method
The purity of aluminum hydroxide powder is relatively high, and the content of toxic substances such as heavy metals such as synthetic polyaluminum chloride is low. Generally, the production process of heating, pressing and acid dissolving is adopted. This process is relatively simple, but the base degree of the produced polyaluminum chloride is low. Therefore, aluminum hydroxide is generally used for heating and acid dissolving, plus calcium aluminate powder for neutralization.
Alumina Method
The raw materials containing aluminum oxide mainly include gibbsite, bauxite, kaolin, coal gangue and so on. The production process can be divided into two steps: the first step is to obtain crystalline aluminum chloride, and the second step is to obtain polyaluminum chloride by pyrolysis or neutralization;
Aluminum Chloride Method
Use aluminum chloride powder as raw material to process polyaluminum chloride. This method is most commonly used. It can be prepared by boiling pyrolysis at 170°C with crystalline aluminum chloride, aging and polymerization with water, solidification and drying.