Synthesis and characterization of a new class of polymeric ligand exchangers for selective removal of arsenate from drinking water

Six new chelating resins were prepared by functionalizing three commercially available XAD resins of various matrix properties, including XAD1180, XAD16 and XAD7HP. Two types of pyridinyl functional groups were loaded on these sorbents, one with two nitrogen donor atoms (2N) per functional group and the other with three N-donor (3N) atoms per functional group. Consequently, six polymeric ligand exchangers (PLE's) were prepared by immobilizing Cu(II) ions onto these chelating resins, where Cu(II) serves as the surface central metal. The highest Cu(II) loading was determined to be 44 mg/g. Unlike standard strong base anion (SBA) exchangers. the PLE's displayed greater affinity toward arsenate than for sulfate. The binary arsenate-sulfate separation factor (alpha(As/S)) ranged from 5.1 to 10. Bench-scale column breakthrough tests confirmed the greater selectivity for arsenate over other common anions (sulfate, bicarbonate and chloride). The breakthrough of arsenate occurred last at similar to 920 BV for XAD1180-3N-Cu. From batch kinetic tests, the PLE's intraparticle diffusivity (D) was determined to be more than one order of magnitude greater than standard SBA resins. The PLE's can be effectively regenerated using 8% NaCl at pH 10. The arsenate capacity can be completely recovered using the brine. Despite the high surface area, the PLE's sorption capacity was limited by the hyper-crosslinkage and the degree of methylation/amination of the template XAD resins. (C) 2010 Elsevier Ltd. All rights reserved.