Effect of silicic acid on arsenate and arsenite retention mechanisms on 6-L ferrihydrite: A spectroscopic and batch adsorption approach
AffiliationUniv Arizona, Dept Soil Water & Environm Sci
Univ Arizona, Dept Chem & Environm Engn
MetadataShow full item record
PublisherPERGAMON-ELSEVIER SCIENCE LTD
CitationGao, X., Root, R. A., Farrell, J., Ela, W., & Chorover, J. (2013). Effect of silicic acid on arsenate and arsenite retention mechanisms on 6-L ferrihydrite: A spectroscopic and batch adsorption approach. Applied Geochemistry, 38, 110-120.
RightsPublished by Elsevier Ltd.
Collection InformationThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at firstname.lastname@example.org.
AbstractThe competitive adsorption of arsenate and arsenite with silicic acid at the ferrihydrite-water interface was investigated over a wide pH range using batch sorption experiments, attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, extended X-ray absorption fine structure (EXAFS) spectroscopy, and density functional theory (DFT) modeling. Batch sorption results indicate that the adsorption of arsenate and arsenite on the 6-L ferrihydrite surface exhibits a strong pH-dependence, and the effect of pH on arsenic sorption differs between arsenate and arsenite. Arsenate adsorption decreases consistently with increasing pH; whereas arsenite adsorption initially increases with pH to a sorption maximum at pH 7-9, where after sorption decreases with further increases in pH. Results indicate that competitive adsorption between silicic acid and arsenate is negligible under the experimental conditions; whereas strong competitive adsorption was observed between silicic acid and arsenite, particularly at low and high pH. In-situ, flow-through ATR-FTIR data reveal that in the absence of silicic acid, arsenate forms inner-sphere, binuclear bidentate, complexes at the ferrihydrite surface across the entire pH range. Silicic acid also forms inner-sphere complexes at ferrihydrite surfaces throughout the entire pH range probed by this study (pH 2.8 - 9.0). The ATR-FTIR data also reveal that silicic acid undergoes polymerization at the ferrihydrite surface under the environmentally-relevant concentrations studied (e.g., 1.0 mM). According to ATR-FTIR data, arsenate complexation mode was not affected by the presence of silicic acid. EXAFS analyses and DFT modeling confirmed that arsenate tetrahedra were bonded to Fe metal centers via binuclear bidentate complexation with average As(V)-Fe bond distance of 3.27 Å. The EXAFS data indicate that arsenite forms both mononuclear bidentate and binuclear bidentate complexes with 6-L ferrihydrite as indicated by two As(III)-Fe bond distances of ~2.92-2.94 and 3.41-3.44 Å, respectively. The As-Fe bond distances in both arsenate and arsenite EXAFS spectra remained unchanged in the presence of Si, suggesting that whereas Si diminishes arsenite adsorption preferentially, it has a negligible effect on As-Fe bonding mechanisms.
Note24 month embargo; published online: 18 September 2013
VersionFinal accepted manuscript
- Competitive sorption of carbonate and arsenic to hematite: combined ATR-FTIR and batch experiments.
- Authors: Brechbühl Y, Christl I, Elzinga EJ, Kretzschmar R
- Issue date: 2012 Jul 1
- Extended X-ray absorption fine structure analysis of arsenite and arsenate adsorption on maghemite.
- Authors: Morin G, Ona-Nguema G, Wang Y, Menguy N, Juillot F, Proux O, Guyot F, Calas G, Brown GE Jr
- Issue date: 2008 Apr 1
- Equilibria, kinetics, and spectroscopic analyses on the uptake of aqueous arsenite by two-line ferrihydrite.
- Authors: Kim SO, Lee WC, Cho HG, Lee BT, Lee PK, Choi SH
- Issue date: 2014 Jan-Feb
- Evidence for different surface speciation of arsenite and arsenate on green rust: an EXAFS and XANES study.
- Authors: Wang Y, Morin G, Ona-Nguema G, Juillot F, Guyot F, Calas G, Brown GE
- Issue date: 2010 Jan 1
- X-ray Absorption Spectroscopic Investigation of Arsenite and Arsenate Adsorption at the Aluminum Oxide-Water Interface.
- Authors: Arai Y, Elzinga EJ, Sparks DL
- Issue date: 2001 Mar 1