As mentioned above, the amide group of polyacrylamide can form hydrogen bonds with many substances. The polymer polyacrylamide forms a "bridge" between the adsorbed particles, and it can also be transformed into a complete flocculant system containing anion, cation, nonionic and zwitterionic ions through chemical conversion or copolymerization. These make polyacrylamide the most ideal and important flocculant at present. Polyacrylamide is widely used in foreign water treatment industry. About 43% of polyacrylamide is used in water treatment in the United States and about 30% in Japan.
nonionic polyacrylamide is suitable for wastewater treatment in chemical industry, oil mining, metallurgy, paper making, electroplating, coal and other industries. Strengthen the rapid solid-liquid separation of wastewater, quickly flocculate a small amount of mechanical impurities contained in wastewater, and achieve the purpose of sewage purification. In use, the dosage is generally controlled at 1 - 15ppm, and the pH of the water system is 6 - 8; Cationic polyacrylamide (c-polyacrylamide) is suitable for the treatment of papermaking water. If about 20ppm c-polyacrylamide is added to the papermaking white water recovery system, satisfactory results can be achieved, and the cost per ton of paper can be saved by more than 10 yuan.
polyacrylamide with high molecular weight (M > 107) and low residue (am < 0.05%) can increase the filtration rate, reduce the sludge volume by 50% and increase the production capacity of waterworks by nearly 40% in the purification of tap water. At present, the traditional industry of alum or other inorganic flocculants is still used in tap water treatment in China. It is estimated that by 2000, China will need more than 80000 tons of polyacrylamide per year in tap water treatment.
Compared with traditional inorganic flocculants, polyacrylamide flocculants have the following advantages:
① there are many varieties and complete specifications, which can meet various conditions and material needs
② small dosage, high efficiency, strong treatment capacity, less sludge, simple post-treatment, organic flocculants such as polyacrylamide and inorganic flocculants can sometimes achieve better results.
