In situ chemical fixation of arsenic-contaminated soils: An experimental study

Abstract

This paper reports the results of an experimental study testing a low-cost in situ chemical fixation method designed to reclaim arsenic-contaminated subsurface soils. Subsurface soils from several industrial sites in southeastern U.S. were contaminated with arsenic through heavy application of herbicide containing arsenic trioxide. The mean concentrations of environmentally available arsenic in soils collected from the two study sites, FW and BH, are 325 mg/kg and 900 mg/kg, respectively. The soils are sandy loams with varying mineralogical and organic contents. The previous study [Yang L, Donahoe RJ. The form, distribution and mobility of arsenic in soils contaminated by arsenic trioxide, at sites in Southeast USA. Appl Geochem 2007;22:320-341] indicated that a large portion of the arsenic in both soils is associated with amorphous aluminum and iron oxyhydroxides and shows very slow release against leaching by synthetic precipitation. The soil's amorphous aluminum and iron oxyhydroxides content was found to have the most significant effect on its ability to retain arsenic. Based on this observation, contaminated soils were reacted with different treatment solutions in an effort to promote the formation of insoluble arsenic-bearing phases and thereby decrease the leachability of arsenic. Ferrous sulfate, potassium permanganate and calcium carbonate were used as the reagents for the chemical fixation solutions evaluated in three sets of batch experiments: (1) FeSO4; (2) FeSO4 and KMnO4; (3) FeSO4, KMnO4 and CaCO3. The optimum treatment solutions for each soil were identified based on the mobility of arsenic during sequential leaching of treated and untreated soils using the fluids described in EPA (SPLP). Both FW and BH soils showed significant decreases in arsenic leachability for all three treatment solutions, compared to untreated soil. While soils treated with solution (3) showed the best results with subsequent TCLP sequential leaching, SPLP sequential leaching of treated soils indicated that lowest arsenic mobility was obtained using treatment solution (1). Treatment solution (1) with only FeSO4 is considered the best choice for remediation of arseniccontaminated soil because SPLP sequential leaching better simulates natural weathering. Analysis of treated soils produced no evidence of newly-formed arsenic-bearing phases in either soil after treatment. Sequential chemical extractions of treated soils indicate that surface complexation of arsenic on ferric hydroxide is the major mechanism for the fixation process.

Retention Studies on Arsenic From Aqueous Solutions by Lime Treated Semi Arid Soils

“…For instance, a distinctive pattern in the mineral samples with soluble contamination was detected with respect to the samples from the accidental spill of pyritic sludge. The increase in the As leaching rate at acid pH in the latter samples is attributed to the solubilization of the sludge itself and related minerals (e.g.,As-jarosite), rather than to the variation of the surface charge as a function of pH [16][17][18][19][20][21][22][23]. The above study suggests lime amendment to be used with caution.…”

Assessment of In Situ Immobilization of Lead (Pb) and Arsenic (As) in Contaminated Soils with Phosphate and Iron: Solubility and Bioaccessibility

“…Under oxidized soil conditions, Fe 2+ can be oxidized to the less soluble Fe 3+ within a few days. The concentration of As in the first step of a sequential extraction, which included the most labile As fraction, was greatly reduced with the FeSO 4 addition (Yang et al 2007). Moore et al (2000) used FeSO 4 to immobilize As in contaminated soils from wood-preserving solution at a timber-framing site and achieved good results.…”

“…In situ immobilization is a cost-effective treatment to remediate As and Pb-contaminated soil and to alleviate the environmental and health hazards (Kim and Davis 2003;Miretzky and Fernandez-Cirelli 2008;Yang et al 2007). For example, cement, quicklime, bone char, and phosphate are used in immobilizing Pb (Cao et al 2008a;Chen et al 2006).…”

Uso de fosfato para remoção de arsênio de solo contaminado

“…A dependên-cia das cargas positivas nas superfícies das argilas com o pH pode ser a responsável pela associação encontrada entre o arsênio e os óxidos de ferro e de alumínio e as argilas silicatadas do tipo 1:1 (caulinita) (Mahimairaja et al, 2005). Em solos ácidos nos quais a superfície das partículas pode estar carregada positivamente, a adsorção específica de arsênio tem sido observada (Waychunas et al, 1993;Yang et al, 2007). O aumento da adsorção do arsênio com o decréscimo do pH e a associação do arsê-nio com os óxidos, oxi-hidróxidos e hidróxidos de ferro, tem sido observado em vários trabalhos (Spuller et al, 2007;Fayiga et al, 2007).…”