Experimental study of surfaces of hydrogel polymers HEMA, HEMA-EEMA-MA, and PVA as adsorbent for removal of azo dyes from liquid phase

Applications of compounds like 2-Hydroxyethylmethacrylate (HEMA), 2-Hydroxyethyl methacrylate-ethoxy ethyl methacrylate-methacrylic acid (HEMA-EEMA-MA), and Polyvinyl alcohol (PVA) as an adsorbent for the removal of two hazardous toxic azo dyes i.e. Malachite green (MG) and Congo red (CR) from aqueous solutions were well explained and elucidated. The adsorbents under consideration were synthesized and characterized by using SEM, and ATR-FTIR. The dye removal depends on the pH of the solution, the optimum pH for this experimentation was found to be 9. The adsorption affinity of MG onto HEMA-EEMA-MA was increased from 245 to 330 mg/g > CR onto PVA 169-236 mg/g > MG onto HEMA 130-205 mg/g > CR onto HEMA-EEMA-MA 90-155 mg/g > MG onto PVA 35-140 mg/g > CR onto HEMA 17-57 mg/g, respectively. Impact of various important physico-chemical parameters i.e. contact time, and it was found that the time required for equilibrium adsorption of MG onto HEMA, HEMA-EEMA-MA and PVA is 80, 90, and 100 min, respectively, and that of CR onto HEMA, HEMA-EEMA-MA and PVA is 70, 80, and 100 min respectively, dye concentration and agitation speed were studied and optimized. The experimental kinetics data was well suited and well fitted to the pseudo-second order model, results clearly depict that the kinetics of the removal of azo dye using polymer adsorbents follows a pseudo-second order model.