Preparation of chitosan-graft-poly(vinyl acetate) copolymers and their adsorption of copper ion

Chitosan-graft-poly(vinyl acetate) copolymers were prepared by a graft copolymerization with a redox initiator, cerium ammonium nitrate. Chitosan molecules not only participated in the reaction, but also served as a role of surfactant. As a result, a stable dispersion solution was observed during the reaction. After drying, particulate membranes were formed because of the rigid chitosan chains at particles' surface. When the membranes were soaked in the water, the hydrophilic chitosan absorbed a great amount of water, but not the hydrophobic poly(vinyl acetate) chains mainly constituted in the core of particles. A two-stage behavior was observed during the adsorption of copper ion in the copolymer membrane. The first stage was governed by both the diffusion and reaction; whereas only diffusion dominated the second stage. The diffusion rate increased with an increase in the amount of chitosan. In order to increase its mechanical strength and acid resistance, the copolymer membrane was cross-linked with a glutaraldehyde. However, the specific adsorption quantity of copper ion decreased as the extent of cross-linking was increased.