Dispersion Polymerization Of Cationic Organic Polymer Floceulant PDMDAAC-AM

Coagulation/flocculation is a widely used process for particle removal in water and wastewater treatment. Quaternary ammonium cationic polyacrylamide become the focuses of research at home and abroad at present as a new high-efficiency organic cationic flocculant. Synthetizing references, cationic copolymer acrylamide-dimethyldiallyl ammonium chloride (PDMDAAC-AM) was synthesized from acrylamide (AM) and dimethyldiallyl ammonium chloride (DMDAAC) by dispersion polymerization. The dispersion system was selected to facilitate the polymerization of AM and DMDAAC. The experiments have been done to choose the applicative stabilizer, medium, cross-linking agent etc and determine their ratio.The optimum operating conditions for preparing PAM-DMDAAC were determined. Kinetics of dispersion polymerization of AM and DMDAAC were researched by measuring the relationship of reaction time and conversion. The structures of the product PDMDAAC-AM were investigated by varies physical chemistry methods. And its application in wastewater was assessed.The main contents and results are following:1. The cationic polyacrylamide was synthesized by dispersion polymerization using the solution of ammonium sulfate as the reaction medium. When the concentration of ammonium sulfate was about 18%, the obtained product was stable. The effect of the other factor on dispersion system were investigated, the monomer concentration of 15%?22.5%, using PVP+PD as composite stabilizer whoes concentration of 2.1% of the system mass, using V50 as initiator whose concentration of 0.01%?0.04% of monomer mass. 2. The effects of various polymerization parameters (e.g., concentration of monomer and initiator, medium polarity, the ratio of AM to DMDAAC, initial temperature and ethylene diamine tetraacetic acid disodium (EDTA)) on the intrinsic viscosity and conversion of copolymer have been investigated. The optimum operating conditions for preparing PAM-DMDAAC were determined as ethanol content 50%, [M] (wt%) 40%, nAM:nDMDAAC 8:2, [I] (wt%) 0.04% and initiate temperature 40°C. On these conditions, the synthesized copolymer with the intrinsic viscosity of 98 cm3/g could be separated, purified and dissolved easily. Adding EDTA can accelerate reaction rate and increase conversion and intrinsic viscosity (molecular weight).3. Kinetics of dispersion polymerization and inverse emulsion polymerization of AM and DMDAAC were investigated. In dispersion polymerization, The rate of polymerization (Rp) increased with the increasing of the molar ratio of AM to DMDAAC, concentrations of monomers, stabilizer and initiator and temperature. The intrinsic viscosity increased with the increasing of the molar ratio of AM to DMDAAC and concentration of monomers and the decreasing of concentrations of stabilizer and initiator. The rate of polymerization and intrinsic viscosity can be represented by Rp?[M]1.44[I]0.60[S]0.39, [?]?[M]1.26[I]-0.13[S]-036. In inverse emulsion polymerization, the influences of the molar ratio of AM to DMDAAC, concentrations of monomers, emulsion and initiator on polymerization is similar with dispersion polymerization. The intrinsic viscosity increased with the increasing of the molar ratio of AM to DMDAAC and concentrations of monomers and emulsion and the decreasing of concentration of initiator. Its kinetics can be expressed as Rp?[M]2.11[I]1.21[E]0.48, [?]?[M]0.87[I]-0.30[E]0.36. The overall activation energy for the rate of polymerization was determined with a dilatometer as 20.33 kJ/mol in inverse emulsion polymerization,29.05 kJ/mol in solution polymerization,37.38 kJ/mol in dispersion polymerization.4. The mechanism of particle generation and propagation in dispersion polymerization is inclined to oligomer precipitation mechanism and grafted copolymer coalescence mechanism. The monomer reactivity ratios of AM (r1) and DMDAAC(r2) were determined by the application of Fineman-Ross methods as 6.664 and 0.120, respectively, The analysis of reactivity ratios revealed that DMDAAC is less reactive than AM, and copolymers formed are statistically in nature.5. The characteristics of polymers synthesized in dispersion polymerization were studied by means of various instrumental analysis techniques, including including infrared spectroscopy, Transmission Electron Microscope, Scanning electron microscopy, thermal analysis et al. The results show that the monomers DMDAAC and AM turn into the copolymer PAM-DMDAAC. The dispersion polymerization is helpful to heat exchange of reaction because of its merits of emulsion.6. The positive charge of PDMDAAC-AM can neutralize the negative charge of sludge particles and leave the sludge off the stable and dehydration. The treatment effect is better than inorganic coagulant ferric chloride polymer. In sludge dewatering experiment it was found that products with high cation degree (2:8 compared with 1:9) have better results both in the dehydration rate and the resistance. However, the increasing of cationic degree can decrease the viscosity of product and raise the prices. Therefore, the products with different ratio can be used to achieve the best cost performance when treating different objects. The turbidity removel of PDMDAAC-AM showed that PDMDAAC-AM had two properties of electricity neutralization and adsorption bridging. In general, the higher the cationic degree and intrinsic viscosity is, the better the turbidity removel is.