e-Journal of Surface Science and Nanotechnology
Online ISSN : 1348-0391
ISSN-L : 1348-0391
Conference -ISSS-7-
Monitoring of Arsenite Sorption to Biogenic Iron Oxide in a Flow-Through Column by X-Ray Absorption Spectroscopy
Yoko FujikawaMasataka SugaharaTetsuo HonmaSayaka HirayamaPhan Do HungShinji SakuraiHiroshi YashimaAyumi HashiguchiShogo TaniguchiHiroaki OzakiPaul Lewtas
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2015 Volume 13 Pages 455-460

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Abstract

We have conducted a pilot study of a biological filtration (BF) system for low-cost arsenic (As) removal from groundwater containing both ferrous iron (Fe(II)) and arsenic (As). Throughout the study, we have observed that arsenite (As(III)) as well as arsenate (As(V)) could be removed with this system. In conventional water treatment technologies, the preoxidation of As(III) to As(V) by oxidizing chemical is a mandatory step for As(III) removal However, such a preoxidation unit has not been used in our BF pilot unit, and hence the mechanisms of As(III) removal by BF have been of interest. Using a flow-through column reactor that simulates the actual BF pond for analysis by X-ray absorption spectroscopy (XAS), we could observe the adsorption of As(III) in water onto iron hydroxides deposited on the biological filter. The time-resolved As K-edge X-ray absorption near-edge structure (XANES) spectra were obtained when the water containing As(III) and Fe(II) was continuously fed to the reactor. An increase in the absorption intensity of the X-ray with time was clearly observed in the time-resolved spectra, indicating that the spectra represented the concentration and chemical state of As adsorbed at the solid-liquid interface of the biological filter. The XAS results also show that while the original water fed to the reactor was supposed to contain only As(III) and Fe(II), a small portion of As(III) was oxidized to As(V) in the influent line when the As(III) solution met the Fe(II) solution before flowing into the reactor. Consequently, besides As(III), As(V) probably formed by the oxidation of As(III) in the influent, was detected on the filter by XAS. The results demonstrate that, in BF, mechanisms of As(III) removal are at least partially explained by the adsorption of As(III) in the raw water to the biological filter as it is. [DOI: 10.1380/ejssnt.2015.455]

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https://creativecommons.org/licenses/by/4.0/deed.ja
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