title: Uptake of arsenate by an alginate-encapsulated magnetic sorbent: process performance and characterization of adsorption chemistry.
abstract: Arsenate removal by a calcium alginate-encapsulated magnetic sorbent was studied. The morphology, microstructure, and composition properties of the sorbent were explored using X-ray diffraction (XRD) and scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDX). The SEM study demonstrates that there are many protuberances and pores on the sorbent surface; the XRD analysis reveals that the sorbent consists of Fe(3)O(4). The EDX analysis indicates that the adsorption on the surfaces of sorbent is highly location dependent. The interaction characteristics between the arsenic and the functional groups on the sorbent were studied by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). These studies indicate that the lattice oxygen in magnetite and the oxygen in hydroxyl of the calcium alginate play important roles in the sorption of arsenate ions onto the sorbent. More importantly, the XPS analysis demonstrates that the arsenate is reduced to arsenite after its adsorption onto the sorbent. It is proposed that divalent iron and the alcoholic group in alginate provide electrons to arsenate. A conceptual model for the adsorption is proposed to illustrate the mechanisms.
authors.affiliation: Division of Environmental Science and Engineering, National University of Singapore, 10 Kent Ridge Crescent, 119260 Singapore.
authors.forename: Soh-Fong
authors.initials: SF
authors.lastname: Lim
authors.forename: Yu-Ming
authors.initials: YM
authors.lastname: Zheng
authors.forename: Shuai-Wen
authors.initials: SW
authors.lastname: Zou
authors.forename: J Paul
authors.initials: JP
authors.lastname: Chen
mesh_terms: D000327:Adsorption; D000464:Alginates / Q000737:chemistry*; D001149:Arsenates / Q000737:chemistry*; D020723:Glucuronic Acid / Q000737:chemistry; D006603:Hexuronic Acids / Q000737:chemistry; D008280:Magnetics; D008855:Microscopy, Electron, Scanning; D010316:Particle Size; D013053:Spectrophotometry; D017550:Spectroscopy, Fourier Transform Infrared; D013499:Surface Properties; D014961:X-Ray Diffraction; D014965:X-Rays
chemical_list: D000464:Alginates; D001149:Arsenates; D006603:Hexuronic Acids; D020723:Glucuronic Acid; C025657:arsenic acid