Performance of a zerovalent iron reactive barrier for the treatment of arsenic in groundwater: Part 2. Geochemical modeling and solid phase studies

Journal Article · Fri Jun 12 00:00:00 EDT 2009 · J. Contam. Hydrol.

DOI:https://doi.org/10.1016/j.jconhyd.2008.12.003· OSTI ID:1005577

Beak, Douglas G; Wilkin, Richard T

Arsenic uptake processes were evaluated in a zerovalent iron reactive barrier installed at a lead smelting facility using geochemical modeling, solid-phase analysis, and X-ray absorption spectroscopy techniques. Aqueous speciation of arsenic is expected to play a key role in directing arsenic uptake processes. Geochemical modeling reveals contrasting pH-dependencies for As(III) and As(V) precipitation. At the moderately alkaline pH conditions typically encountered in zerovalent iron reactive barriers, As(III) is unlikely to precipitate as an oxide or a sulfide phase. Conversely, increasing pH is expected to drive precipitation of metal arsenates including ferrous arsenate. Bacterially mediated sulfate reduction plays an important role in field installations of granular iron. Neoformed iron sulfides provide surfaces for adsorption of oxyanion and thioarsenic species of As(III) and As(V) and are expected to provide enhanced arsenic removal capacity. X-ray absorption near edge structure (XANES) spectra indicate that arsenic is sequestered in the solid phase as both As(III) and As(V) in coordination environments with O and S. Arsenic removal in the PRB probably results from several pathways, including adsorption to iron oxide and iron sulfide surfaces, and possible precipitation of ferrous arsenate. Corrosion of granular iron appears to result in some As(III) oxidation to As(V) as the proportion of As(V) to As(III) in the solid phase is greater compared to influent groundwater. As(0) was not detected in the PRB materials. These results are broadly comparable to laboratory based studies of arsenic removal by zerovalent iron, but additional complexity is revealed in the field environment, which is largely due to the influence of subsurface microbiota.

• Research Organization: Argonne National Lab. (ANL), Argonne, IL (United States)
• Sponsoring Organization: USDOE
• OSTI ID: 1005577
• Journal Information: J. Contam. Hydrol., Vol. 106, Issue (1-2) ; 04, 2009; ISSN 0169-7722
• Country of Publication: United States
• Language: ENGLISH

Related Subjects

54 ENVIRONMENTAL SCIENCES
ABSORPTION
ABSORPTION SPECTROSCOPY
ADSORPTION
ARSENATES
ARSENIC
CAPACITY
CORROSION
ENVIRONMENT
IRON
IRON OXIDES
IRON SULFIDES
LEAD
MATERIALS
METALS
OXIDATION
OXIDES
PERFORMANCE
PH VALUE
PHASE STUDIES
PRECIPITATION
REDUCTION
REMOVAL
SIMULATION
SMELTING
SOLIDS
SPECTRA
SULFATES
SULFIDES
SURFACES
UPTAKE