Removal of model cationic dye by adsorption onto poly(methacrylic acid)/zeolite hydrogel composites: Kinetics, equilibrium study and image analysis

Abstract

Composites based on poly(methacrylic acid) (PMAA) and two types of zeolite, hydrophilic zeolite A and hydrophobic zeolite ZSM-5, were synthesized. The obtained hydrogel composites that combine well the strong interaction between PMAA and cationic species, the accessibility of active sites in the swollen network and fine mechanical stability of zeolites are considered promising candidates for removal of cationic dye, basic yellow 28 (BY28) from aqueous solutions. The adsorption was found to be highly dependent on composition of hydrogel composites, initial dye concentration, solution pH, sorbent mass and temperature, while the effect of zeolite type is less manifested. It was found that the surface adsorption influenced the kinetics of adsorption which was determined by the rate of movement of the boundary layer of BY28 adsorbed on hydrogel surface. Adsorption processes were found to be favorable and preferably physical in nature with maximum adsorption capacity that could reach up to 180mg/g for PMAA/30A hydrogel composite. Image analysis was applied on differently colored hydrogels and revealed the linear correlation between equilibrium adsorption capacities and the mean values of pixel intensity, as well as the strong effect of initial dye concentration on uniformity of coloration along the hydrogel diameter.