Synthesis of a new chelating resin bearing amidoxime group for adsorption of Cu(II), Ni(II) and Pb(II) by batch and fixed-bed column methods

Abstract

A new amidoxime chelating resin (PAO-AM) was synthesized from the functionalization of poly(acrylamide-co-N,N′-methylenebisacrylamide) (CPM) supported acrylonitrile group (CPM-EA-AN) with hydroxylamine under alkaline conditions. The CPM-EA-AN was prepared by treatment of CPM with ethylenediamine; the amino group in CPM-EA was reacted with acrylonitrile to give CPM-EA-AN. The resulting chelating resin was characterized with FTIR spectroscopy, scanning electron microscopy (SEM), thermogravimetric analysis (TGA), water regain and Brunauer–Emmett–Teller (BET). Batch experiments were performed to study the effects of solution pH, metal ions concentration, contact time and adsorption temperature on metal ion adsorption. It was found that PAO-AM showed high affinity toward Cu(II), Ni(II) and Pb(II) ions. The maximum adsorption capacities were found to be 2.3, 1.94 and 1.14mmol/g resin for Cu(II), Ni(II) and Pb(II), respectively. The adsorption isotherms were analyzed using the Langmuir, Freundlich and Temkin isotherms. The adsorption isotherms were better fitted by the Langmuir equation. The kinetics data were analyzed by pseudo-first order, pseudo-second order, and intra-particle diffusion equations. The results showed that the adsorption process could be described by pseudo-second-order kinetic model. Thermodynamic parameters revealed the spontaneity of adsorption process and higher temperatures favor the adsorption process. Additionally, the adsorption performance of (PAO-AM) toward Cu(II), Ni(II) and Pb(II) using fixed bed column method was investigated. Regeneration of chelating resin loaded with metal ions was effectively performed and the resin could be used repetitively for 5 times with a small decrease in adsorption capacity.