title: Removal of methylated arsenic in groundwater with iron filings.
abstract: Field and laboratory experiments were conducted to study the potential use of Fe filings to remove monomethyl arsenate (MMA) and dimethyl arsenate (DMA) from contaminated waters. Batch experiments show that the affinity of MMAfor Fe filings is comparable to that of inorganic arsenate, but lower than that for arsenite. In contrast, very little DMA was retained by Fe filings or their corrosion products. The wide range of affinities of different As species for Fe filings was confirmed by a series of retention and selective-leaching experiments using small columns and As-spiked groundwater. The effectiveness of Fe filings was also demonstrated with a field deployment at a U.S. Superfund site where groundwater is highly contaminated with both organic and inorganic As species. Over the course of 4 months, a 3 L cartridge of Fe filings removed > 85% of As contained in 16000 L of groundwater containing 1-1.5 mg/L total dissolved As, approximately 30% of which was organic As. The results indicate that Fe filings could be used to treat groundwater contaminated with MMA, which is the main organic form of As at most contaminated sites. Indications of partial demethylation in the column of Fe filings suggest conditions might be optimized further to enhance the removal of DMA.
authors.affiliation: Lamont Doherty Earth Observatory of Columbia University, 61 Route 9W, Palisades, New York 10964, USA. czhongqi@ldeo.columbia.edu
authors.forename: Zhongqi
authors.initials: Z
authors.lastname: Cheng
authors.forename: Alexander
authors.initials: A
authors.lastname: Van Geen
authors.forename: Roseline
authors.initials: R
authors.lastname: Louis
authors.forename: Nikolaos
authors.initials: N
authors.lastname: Nikolaidis
authors.forename: Richard
authors.initials: R
authors.lastname: Bailey
mesh_terms: D001149:Arsenates / Q000032:analysis* / Q000737:chemistry; D005618:Fresh Water / Q000737:chemistry*; D007501:Iron / Q000737:chemistry*; D013058:Mass Spectrometry; D013054:Spectrophotometry, Atomic; D014874:Water Pollutants, Chemical / Q000032:analysis*; D014876:Water Pollution / Q000517:prevention & control*; D018508:Water Purification / Q000379:methods*
chemical_list: D001149:Arsenates; D014874:Water Pollutants, Chemical; D007501:Iron