Iron(III) complex of an amino-functionalized poly(acrylamide)-grafted lignocellulosic residue as a potential adsorbent for the removal of chromium(VI) from water and industry effluents

A new adsorbent (AM-Fe-PGCP), iron(III) complex of an amino-functionalized poly(acrylamide)-grafted coconut coir pith(CP) was prepared through graft copolymerization of acrylamide onto CP (a lignocellulosic residue) in the presence of N, N′-methylenebisacrylamide as cross-linker using and potassium persulphate as an initiator, followed by loading with Fe(III) in the presence of HCl and was tested for its ability to recover chromium(VI) from water and industry effluents. The adsorbent was characterized using FTIR, SEM, XRD, TG/DTG, Surface area analyzer and potentiometric titrations. The potential of the AM-Fe-PGCP to adsorb Cr(VI) from aqueous solutions was investigated under different optimized conditions of pH, concentration of Cr(VI), contact time, and temperature. The effective pH for the removal of Cr(VI) was 4.0. Kinetic data followed a pseudo-second-order model. The equilibrium data were correlated with the Langmuir isotherm model. The equilibrium Cr(VI) sorption capacity was estimated to be 90.09 mg g^-1. Quantitative removal of 27.7 mg L^-1 Cr(VI) from 1.0 L of electroplating industry wastewater was achieved by 0.5 g adsorbent. The reusability of the adsorbent was demonstrated over four cycles using 0.1 M NaOH solution.