DIFFUSION-LIMITED SORPTION OF DYES ON MODIFIED ACRYLICS AND ACRYLIC COPOLYMERS

Acrylonitrile was polymerized using a redox system. The polyacrylonitr ile was modified by heating with aqueous 50% H2SO4 or with aqueous 50% NaOH. Acrylonitrile was also copolymerized with acrylic acid or acryl amide or methylenebisacrylamide using a redox system. The sorption abi lities of the modified acrylics and copolymers were determined from aq ueous solutions of two dyes, namely methylene blue and alizarin yellow R. The porous structure of the polymers was determined by using mercu ry porosimetry. The experimental results of the dye uptake were theore tically treated by using a diffusion-limited adsorption method. The eq uation was applied for short reaction times and the parameters were gr aphically determined from log-log plots: the specific rate constant k' from the intercept A and the parameter n (0 < n < 1) from the slope. The diffusion coefficient D was calculated from Fick's equation. The r esults were discussed taking into consideration the pore structure of the polymers as well as the 'pore model' and the 'free volume model' o f the diffusion process. The electron donor-acceptor interactions betw een the functional groups of the polymers and the functional groups of the dyes strongly influence the sorption process.