Synthesis Of Aqueous Dispersion Of Amphoteric Polyacrylamide And Its Flocculation Properties

A rapid increase in population, the rapid development of industry and many other factors lead to water shortage and water pollution, water pollution has become more and more serious since the twentieth century. Flocculating settling process is a simple and economic method of water treatment, in order to improve the flocculation efficiency, a kind of green water treatment agent, amphoteric polyacrylamides, has been proposed and synthesized. Amphoteric polyacrylamide has been used widely because of its less dosage, low toxicity, and could be used over a wide range of pH in waste water treatment. Aqueous dispersion polymerization is one of the latest technologies in preparing amphoteric polyacrylamide, it has many advantages such as the inherent simplicity of single-step process, avoiding secondary pollution of organic solvents and so on. In a word, it is a green technology.In this paper, amphoteric copolymer poly(acrylamide-co-itaconic acid-co-acryloyloxyethyltrimethyl ammonium chloride-co-methacryloyloxyethyl trimethyl ammonium chloride)(P(AM-co-IA-co-DAC-co-DMC)) was prepared by dispersion polymerization in the solution of ammonium sulfate using2,2’-azobis (2-amidinopro-pane) dihydrochloride (AIBA) as the initiator. The morphology of the product was observed by transmission electron microscopy (TEM) and the particle size and its distribution was measured by Particle Size Analyzer. To prepare stable dispersions, the effects of ammonium sulfate concentration, total monomer, the molar ratio of different monomers, initiator and stabilizer content on the stability of the dispersion polymerization were investigated.The results of the experiments revealed that the concentration of ammonium sulfate, stabilizer, total monomer and initiator has important effect on the products. With increasing the concentration of ammonium sulfate, the intrinsic viscosity and apparent viscosity decreased; with the increase of the initiator concentration gave rise to an increase in intrinsic viscosity at first and then decrease, and the same to the stabilizer concentration; when the total monomer concentration was lower than11wt%, as the monomer concentration increased, the product of apparent viscosity, average particle size and intrinsic viscosity showed an increasing trend, but the monomer concentration was over11%, with the monomer mass fraction increased further, the intrinsic viscosity decreased while the apparent viscosity and average particle size increased; when the total monomer concentration exceeded15wt%, the product is easy to gel. The results showed a stable system was obtained under the following optimized conditions:concentrations of10wt%～16wt%for PDAC,16wt%-25wt%for ammonium sulfate,0.5%-0.9%for initiator, n+:n(?)=1/2-1/4, monomer content is10%to13%, reaction temperature45℃and reaction time is15h.The flocculation performance of the copolymer was investigated in kaolin suspension; the effects of addition dosage, intrinsic viscosity, the pH value of the system, temperature and monomer ratio on flocculation were investigated. The results showed that transmittance of supernatant liquid was98.7at room temperature when n+/n-=3:1, addition dosage is3mg/L and intrinsic viscosity is3.16dL/g. It was found that amphoteric acrylamide is more efficient in flocculation behavior as compared to cationic or anionic polyacrylamide,especially in alkaline conditions, the flocculation effect is greatly improved.