An adsorption kinetic study of ionic dyes by polyampholyte star polymers

The aim of this work was to merge the characteristics of star polymers with polyampholytes to address the issue of treating colored wastewater. To achieve the intended objective, homopolymers derived from acrylic acid were synthesized using reversible addition-fragmentation chain transfer (RAFT) polymerization with the monomer/RAFT agent ratios of 70, 130, and 200. The homopolymers were linked to the poly(2-(dimethylamino)ethyl acrylate) core using RAFT polymerization in an inverse emulsion polymerization. Star polymers had molecular weight 45 times more than homopolymers with worm-like structures, spheres of various sizes, cubic, and hexagonal morphologies during self-assembly studies at pH = 2, 4.5, 8, and 10. This study investigated the adsorption characteristics of methyl orange (MO) and methylene blue (MB), as well as their concurrent adsorption which were affected by pH, time, molecular weight, and dye concentration. At pH = 10, MB adsorption was maximum, whereas MO adsorption was the highest at pH = 2. Simultaneous adsorption of two dyes showed a similar pattern, although electrostatic forces may result in reduced adsorption. Moreover, adsorption effectiveness increased with molecular weight. Fitting the adsorption data with pseudo-second-order (PSO) kinetic model and Freundlich isotherm suggested that the adsorption process occurring on heterogeneous adsorbent surfaces can be attributed to chemisorption.