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This post was last edited by wang*neng on 2018-12-4 09:54. Based on years of production experience, it has been concluded that there are several issues associated with the production of polyaluminum chloride. I. Basicity issue: The higher the basicity, the better the flocculation effect of polyaluminum chloride is usually. In products with low basicity, aluminum shavings, sodium aluminate, calcium carbonate, aluminum carbonate, sodium hydroxide gel, lime, and similar substances can be added to increase the basicity. II. Product purity issue: The alumina content is an important indicator for polyaluminum chloride products. It is generally believed that the higher this content, the higher the purity, which indicates better quality. III. The issue of removing harmful ions such as heavy metals: Some raw materials contain high levels of such harmful ions. During the acid dissolution process, sulfides such as sodium sulfide and calcium sulfide can be added to convert these harmful ions into sulfide precipitates, thereby removing them. Additionally, methods such as replacement with aluminum shavings and adsorption using activated carbon can also be considered to remove harmful ions like heavy metals. IV. The issue of insoluble substances: **Standards specify exact limits for the content of insoluble substances in commercially available polyaluminum chloride. Domestic manufacturers generally use minerals as raw materials, and such minerals have complex compositions; they need to be crushed to produce powder. The finer the powder, the higher the rate of alumina dissolution, and consequently, it becomes more difficult to precipitate impurities such as insoluble substances. Therefore, how to effectively reduce insoluble substances is an issue that requires close attention in the production of polyaluminum chloride. V. Regarding the amount of hydrochloric acid to be used, in practice, the higher the concentration of hydrochloric acid, the greater the dissolution rate of alumina. However, the more volatile hydrochloric acid becomes as well. Therefore, it is necessary to determine an appropriate concentration for hydrochloric acid; generally, this concentration is around 20% by mass. When less hydrochloric acid is used, the dissolution rate of alumina is low, while excessive use results in polyaluminum chloride with a low basicity and high corrosiveness. Transportation is difficult; therefore, to produce high-quality polyaluminum chloride, it is necessary to add hydrochloric acid in an appropriate amount.