Inorganic Flocculant Polymeric Aluminum Chloride and Polymeric Ferric Chloride Inorganic Flocculant is the earliest application of flocculant, ancient China has already begun to use alum to water purification, until the United States to develop aluminum sulfate, people on the application of inorganic flocculant and R & D, it entered a new stage of development. Inorganic polymer raw materials from a wide range of sources, low prices, the best scope for a wide range of drugs, but its relative molecular mass and particle size is not high enough, the adsorption capacity of aggregates is not strong enough, especially for the adsorption of colloidal bridging capacity than organic Many polymer poor, and there is more dosage, the amount of sludge generated, post-treatment which shortcomings. (1) polyaluminum chloride flocculant. Poly aluminum chloride can be hydrolyzed to produce high-valent ions to form various types of hydroxyl polynuclear complexes. These hydroxyl polynuclear complexes are metastable by carbonyl-type bridging. Among them, the ratio of OH- and AL3 + concentration (generally referred to as basal salinity or alkalinity, expressed as a percentage) has the greatest effect on the flocculation effect. Under normal circumstances, the higher the base of the salt, the greater the effect of flocculation, but the high base of the salt itself easily generate insoluble aluminum hydroxide precipitation, resulting in reduced flocculation. Studies have shown that the best base of the salt at 75% -85%, floc production at this time fast, large particles and heavy precipitation performance. Polyaluminum chloride with a small dosage, rapid settling velocity, dense particles, in addition to the obvious effect of removing turbidity and other characteristics, in industrial water treatment, has been widely used. It is noteworthy that aluminum, especially active aluminum, is more toxic and at the same time due to the poor preparation of polyaluminum chloride, more fine particles of hydrolyzed aluminum are present in the solution, which to some extent limits the polymerization Use of aluminum chloride. However, by improving the coagulation reaction conditions, to extend the slow coagulation time, can effectively reduce the aluminum content in water. (2) Polymeric aluminum ferric chloride flocculant. Poly aluminum ferric chloride is another new type of inorganic flocculant, the flocculation mechanism similar to polyaluminum chloride. Poly aluminum ferric chloride main types of polyferric sulfate, polyaluminum chloride, polychlorinated ferric sulfate and so on. Among them, polychlorinated ferric sulfate in addition to the characteristics of aluminum salt inorganic polymer flocculant, but also has a low price, PH value for a wide range of applications. However, in general, polyaluminum chloride requires a relatively low degree of basicity of the alkalinity, and generally it is necessary to control the amount of OH-species to 8% to 15% of that of Fe3 +. Beyond this range, the ferrohydrolysis reaction will be abrupt changes from the high price of polymeric hydroxyl complex ions into cheap polymeric gelling products. In addition, PACF product stability is poor, the polymerization within a few hours to one week that turned to precipitation, so that the flocculation effect is reduced, so its application is far less than polyaluminum chloride.