To understand the difference between the modified single cation and multiple cation in CPAM, first of all let’s talk about what the modified single cation polyacrylamide is. In addition to the poly-aluminium chloride and poly-ferric, poly-activated silica gel and its modified products are also commonly used as the modified single cation inorganic flocculants, such as PSAF and PPAF. The purpose of modification is to introduce some high charged ions in order to enhance the ion neutralizing ability, by introducing hydroxy and phosphate radical so as to increase the coordination complex ability, then further changing the flocculation effect, the possible reason is that some anion or cation is able to change the polymer structure and distribution, or there is an effect of synergistic enhancement between more than two kinds of polymers.

In recently years some compound inorganic flocculants and compound inorganic high molecule flocculants have been developed in succession. PSAA, a new type of inorganic high molecule flocculant, with the characters of simple production, wide material sources and low cost, has the better oil removal ability in the heavy oil producing water treatment of oil field, thus it has great development value and wide application future. Another flocculant PFSS, we find that high polymerized silicic acid and metal ions can produce good coagulating effect. By introducing the metal ion into the polysilicate, the average molecular weight of the flocculants can reach up to 2 x 105, which might partially replace the organic compound high molecule flocculants in the water treatment.

The commonly used modified multiple CPAM inorganic flocculant is PAFCS, and in the drinking water and wastewater treatment, it has better effect than the alums. In the oily wastewater and printing and dyeing wastewater treatment, PAFCS has better effect and better decoloring ability than PAC. It also has the advantages such as larger flocs proportion, faster flocculating speed, easy to filter and high water outlet. Its raw material comes from the industrial waste so the cost is less, which is suitable for the industrial water treatment. The aluminium and ferric copolymerized compound flocculant also belongs to this kind of product, its production material aluminim chloride and ferric chloride are both cheap conventional inorganic flocculants, its wide source and simple production benefit its development and application. The copolymer of aluminium and ferric is different from the mixture of the two, it is a flocculant more efficiently synthesizing the advantage of PAC and FeCl3, and enhancing the turbidity removal effect.

With the better knowledge of the water treatment, the toxic effect of aluminium residues to the organism attracts more and more attention from the society, and the question how to reduce the second pollution has been brought to the forefront. The domestic current production method for the drinking water causes the aluminium content 1 - 2 times than the raw water. The reason why drinking water contains high aluminium residues might lie in the deficient flocculation process, which causes some aluminium to be contained in the form of aluminium hydroxide micro granular in the water. Applying strengthened flocculation cleaning method, improving the conditions of flocculating reaction, and prolonging the slow flocculating time can effectively reduce the aluminium content. Considering the inorganic flocculants might have some corrosivity and toxicity to the human health and ecological environment, people have developed the organic high molecule flocculants.

The production and application of inorganic high molecule flocculants in China have been made significant progress, the research of the most representative poly aluminium chloride and polymeric ferric sulfate has occupied the first row of the world. The organic and inorganic compound flocculants with the characteristics of numerous variety and property take the predominant place in the market. The mechanism of reaction is related with the synergism. The inorganic high molecule part absorbs impurities and suspending micro particles to form some bigger and bigger granules, while the organic high molecule part by its bridging and net capturing function which uses the activated groups attached on the high molecules, captures the other impurities together to precipitate. At the same time, the existence of the inorganic has the charges neutralize in the pollutant surfaces, enhances the organic high molecule flocculation, and greatly improves the flocculating effect.