title: Different modes of adsorptions of arsenate on silica grafted with Fe3+-coordinated silanes.
abstract: In order to optimize the adsorption of arsenate, we prepared silica based adsorbents by grafting Fe(3+)-coordinated N-(2-aminoethyl)-3-aminopropyltriethoxysilanes (aeaptes) in various Fe:aeaptes ratios (mixing ratios). Two kinds of mesoporous silica (MCM-41 and SBA-15) and fumed silica (Cab-O-sil M7D) were used as substrates. The adsorption of arsenate saturated at As/Fe=1, 2 and 3 on mesoporous silica based adsorbents from with Fe:aeaptes ratios of 1:1, 1:2 and 1:3, respectively. On the other hand, saturation occurred at As/Fe=1 on Cab-O-sil M7D-based adsorbents for all three Fe:aeaptes ratios. In addition to this dependence of the adsorption on the coordination conditions, two different modes were clearly distinguished in the adsorption isotherm for the MCM-41 based adsorbent prepared with a Fe:aeaptes ratio of 1:1. These two distinct adsorptions are likely to be due to the induction of well-defined coordination structures by this method. This result is significantly different from that found in a previous study where adsorbents were prepared by the grafting of aeaptes followed by the coordination of Fe(3+), where a single mode of adsorption was observed. The adsorptions were further analyzed using the Langmuir equation and by X-ray adsorption spectroscopy.
authors.affiliation: Division of Materials Science and Chemical Engineering, Yokohama National University, 79-5 Tokiwadai, Hodogaya-ku, Yokohama 240-8501, Japan.
authors.forename: Ryo
authors.initials: R
authors.lastname: Otsuka
authors.forename: Hideaki
authors.initials: H
authors.lastname: Yoshitake
mesh_terms: D000327:Adsorption; D001149:Arsenates / Q000302:isolation & purification*; D056831:Coordination Complexes / Q000737:chemistry*; D005290:Ferric Compounds / Q000737:chemistry*; D060587:Groundwater / Q000737:chemistry*; D012821:Silanes / Q000737:chemistry*; D012822:Silicon Dioxide / Q000737:chemistry; D014874:Water Pollutants, Chemical / Q000302:isolation & purification*; D056928:X-Ray Absorption Spectroscopy
chemical_list: D001149:Arsenates; D056831:Coordination Complexes; D005290:Ferric Compounds; C509968:MCM-41; C509969:SBA-15; D012821:Silanes; D014874:Water Pollutants, Chemical; D012822:Silicon Dioxide; C025657:arsenic acid
keywords: Arsenate adsorption; Fe-amine complexes; Grafting of organosilane; Mesoporous silicas