title: XAFS study of starch-stabilized magnetite nanoparticles and surface speciation of arsenate.
abstract: It has been shown that starch can effectively stabilize nanoscale magnetite particles, and starch-stabilized magnetite nanoparticles (SMNP) are promising for in situ remediation of arsenic-contaminated soils. However, a molecular level understanding has been lacking. Here, we carried out XAFS studies to bridge this knowledge gap. Fe K-edge XAFS spectra indicated that the Fe-O and Fe-Fe coordination numbers of SMNP were lower than those for bare magnetite particles, and these coordination numbers decreased with increasing starch concentration. The decrease in the average coordination number at elevated stabilizer concentration was attributed to the increase in the surface-to-volume ratio. Arsenic K-edge XAFS spectra indicated that adsorbed arsenate on SMNP consisted primarily of binuclear bidentate (BB) complexes and monodentate mononuclear (MM) complexes. More BB complexes (energetically more favorable) were observed at higher starch concentrations, indicating that SMNP not only offered greater adsorption surface area, but also stronger adsorption affinity toward arsenate.
authors: State Key Laboratory of Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, People's Republic of China. myzhang@rcees.ac.cn
authors: Meiyi
authors: M
authors: Zhang
authors: Gang
authors: G
authors: Pan
authors: Dongye
authors: D
authors: Zhao
authors: Guangzhi
authors: G
authors: He
mesh_terms: D000327:Adsorption; D001149:Arsenates / Q000737:chemistry*; D052918:Environmental Restoration and Remediation / Q000295:instrumentation*; D058185:Magnetite Nanoparticles / Q000737:chemistry*; D013213:Starch / Q000737:chemistry*; D013499:Surface Properties; D014874:Water Pollutants, Chemical / Q000737:chemistry*; D056928:X-Ray Absorption Spectroscopy
chemical_list: D001149:Arsenates; D058185:Magnetite Nanoparticles; D014874:Water Pollutants, Chemical; D013213:Starch