| On the basis of the relevant literatures, the preparation rules and the swelling property on the aqueous dispersion of amphoteric polyacrylamide were investigated in this thesis. At the same time, the performances of the coagulation-flocculation were discussed.1. Acrylamide(AM) was selected as main raw material, dimethylaminoethyl methacrylate methyl chloride (DMC) as the cationic co-monomer, acrylic acid as the anionic co-monomer, poly(dimethylaminoethyl methacrylate methyl chloride) (PDMC) as stabilizer and azo-compounds(V-50) as initiator, the amphoteric polyelectrolyte of P(DMC/AM/AA) was synthesized by the aqueous dispersion polymerization in the ammonium sulfate solution.2. The effects of varying factors, i.e. the sorts and concentration of inorganic salt, the concentration and molecular weight of the stabilizer, the total concentration of monomers and the molar ratios of DMC:AM:AA , the concentration of initiator, the temperature and the pH value of the system on the polymerization process, product characters (such as molecular weight, particle size and size distribution) and the stability of the system were investigated. By the single-factor experiments, the optimum conditions of synthesis were determined as follows: the concentration of ammonium sulfate28%~32%, the concentration of stabilizer 2.0%~4.0%, the molecular weight of stabilizer 20.0×104~57.0×104, the monomer concentration 8%~15%, the pH value of the system 5.0, and the reaction temperature 50~60℃.By the orthogonal experiment, the optimum conditions of synthesis were determined as follows: the concentration of stabilizer 3.0%, the concentration of initiator 400mg·L-1, the concentration of ammonium sulfate 30%, and the initiation temperature 60℃.3. The aqueous dispersion copolymers were characterized with Fourier Transform Infra-Red (FTIR), it revealed that the main chain units of AM,AA,DMC were showed in the FTIR figure, and all of the monomers participated in the polymerization. Utilizing the optical microscope, the morphology of copolymer particles were observed. The particles were basically round shape, the slide was smooth, and the size was in average. Utilizing the Laser Particle-size Analyzer, the particle size and size distribution of the aqueous dispersion were characterized. The average particle size was 2.31μm. The stability of the aqueous dispersion was good, it didn't delaminate in half a year.4. Utilizing the digital rotational viscometer, the Laser Particle-size Analyzer, and the optical microscope, the swelling properties of the aqueous dispersion were studied. The apparent viscosity of the system, the size distribution of the aqueous dispersion, and the morphology of copolymer particles in the swelling course were investigated with the variables of rotation speed and inorganic salts concentration. It revealed that, with decreasing the concentration of ammonium sulfate, the apparent viscosity of the aqueous dispersion and the particle size increased, and the system became less stable, most of the particles swelled or dissolved in the ammonium sulfate solution.5. The prepared copolymer P(DMC/AM/AA) was used as flocculant to treat the simulate waste water of kaolin suspended solution. The influences of the dosage, the cationic and anionic degree, and the pH value on flocculation efficiency were investigated. The different types of organic flocculant, inorganic flocculant (PAC) and the cooperation of them on the flocculation efficiency were investigated. It was found that the pH value had little effect on the flocculation efficiency of amphoteric polyacrylamide, which was better than that of cationic and nonionic polyacrylamide. Better flocculation efficiency could be obtained when they cooperated with inorganic flocculant PAC in the treatment of waste water, and the dosage could be decreased.
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