Novel hexamethylene diamine-functionalized macroporous copolymer for chromium removal from aqueous solutions

Abstract

Macroporous copolymers of poly[(glycidyl methacrylate)-co-(ethylene glycol dimethacrylate)] (PGME) with various crosslinker (ethylene glycol dimethacrylate) concentrations and porosity parameters and additionally functionalized with hexamethylene diamine (PGME-HD) were tested as potential Cr(VI) oxyanion sorbents from aqueous solutions. Kinetics of Cr(VI) sorption was investigated in the temperature range 298–343 K and the results were fitted to chemical reaction and particle diffusion models. The Cr(VI) sorption obeys the pseudo-second-order model with definite influence of pore diffusion. A temperature rise promotes chromium removal, with a maximum experimental uptake capacity of 4.21 mmol g−1 at 343 K for the sample with the highest amino group concentration. Equilibrium data were analysed with Langmuir, Freundlich and Temkin adsorption isotherm models. Thermodynamic parameters, i.e. Gibbs free energy (ΔG0), enthalpy (ΔH0) and entropy change (ΔS0) and activation energy of sorption (Ea), were calculated. The Cr(VI) adsorption onto PGME-HD was found to be spontaneous and endothermic, with increased randomness in the system. Desorption experiments show that chromium anion sorption was reversible and the PGME-HD sample GMA 60 HD was easily regenerated with 0.1 mol L−1 NaOH up to 90% recovery in the fourth sorption/desorption cycle. In the fifth cycle, a substantial sorption loss of 37% was observed. © 2016 Society of Chemical Industry.