Synthesis and Characterization of Graft Polyelectrolytes

Abstract

<p> Water soluble polymers are used as flocculants in wastewater treatment, mineral processing, and pulp and paper production. The work in this thesis focuses on the synthesis of graft polyelectrolytes and the efficiency of the copolymers in flocculation. It was proposed that it would be advantageous to have clusters of high charge that can adsorb strongly to the particle surface, and a long chain of nonionic polymer to bridge the particles together.</p> <p> Electrolyte copolymers were produced using a high molecular weight polyacrylamide as the backbone polymer and a redox agent, ceric ammonium nitrate, to form a radical site on the polymer. DADMAC monomer was polymerized from these radical sites producing grafts of cationic charge. The copolymers were produced at a range of polymerization conditions including PAM concentration, amount of nitric acid, amount of ceric ion and polymerization temperature. Grafting was successful and homopolymerization of DADMAC was found not to occur. The graft polymers were characterized using NMR, charge titration, viscosity measurements, and gel fraction measurements.</p> <p> The copolymers were tested for flocculating properties using a model TiO2 system. The graft copolymers produced performed better than the backbone polyacrylamide, low and high molecular weigh polyDADMAC, and a commercial random copolymer of acrylamide and DADMAC. It was found that both the amount of charge and gel is very important in flocculation performance. However, the testing of the copolymers as a conditioner for a municipal sludge did not show improvement in the drainage rate.</p>