HR: 11:20h
AN: H32C-05    [Abstracts]
TI: Removal of Arsenic(III) from Groundwater with Nano Scale Zero-Valent Iron
AU: * Manning, B A
EM: bmanning@sfsu.edu
AF: San Francisco State University, 1600 Holloway Avenue, San Francisco, CA 94132 United States
AU: Kiser, J
EM: jkiser@sbcglobal.net
AF: San Francisco State University, 1600 Holloway Avenue, San Francisco, CA 94132 United States
AU: Kanel, S R
EM: skanel@gist.ac.kr
AF: Gwangju Institute of Science and Technology, 1 Oryong-dong, Buk-gu, Gwangju, 500-712 Korea, Republic of
AU: Choi, H
EM: hcchoi@gist.ac.kr
AF: Gwangju Institute of Science and Technology, 1 Oryong-dong, Buk-gu, Gwangju, 500-712 Korea, Republic of
AB: Arsenite (As(III)) is a highly toxic, soluble species that is a naturally occurring groundwater contaminant of environmental concern. There is a need for detailed information about the natural geochemical cycling of As(III), including the fundamental chemical mechanisms of the reactions of As(III) with a variety of surfaces, both natural and engineered. In this paper we focus on the development of ultra-fine, synthetic nanoscale zero-valent iron (nano-Fe(0)) material as both a potential candidate for As(III) remediation and a high surface area model compound to study the remediation of groundwater containing As(III) with larger Fe(0) particles. A variety of techniques were used including SEM, AFM, XRD, and X-ray absorption spectroscopy (XAS) to characterize particle size, surface morphology, corrosion layers formed, and As(III)-nano-Fe(0) surface complexation chemistry. Results from AFM showed particle size ranged from 1-120 nm. XRD and SEM results revealed that nano-Fe(0) gradually converted to magnetite/maghemite corrosion products mixed with lepidocrocite over 60 d. Arsenic(III) batch adsorption kinetics were rapid following a pseudo-first-order rate expression with observed reaction rate constants (kobs) of up to 1.3 per min (at varying Fe(0) densities). These values are about 1000 times higher than kobs literature values for As(III) adsorption on micron size Fe(0). Results from laser light scattering (electrophoretic mobility) and XAS confirmed that inner-sphere surface complexation occurred on nano-Fe(0) corrosion products. In addition, oxidation of As(III) to As(V) was evident in batch experiments. Addition of 10 mM anions (bicarbonate, sulfate, nitrate, and arsenate) had no effect on the uptake of As(III) whereas 10 mM silicic acid and phosphate reduced the uptake of As(III) from 99.9% to 44.9 and 66.3%, respectively. Our results suggest that nano-Fe(0) is an appropriate material for further investigation of the feasibility of using Fe(0) for As(III) remediation.
DE: 1831 Groundwater quality
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting