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08:01
Removal of Arsenic Using a Cationic Polymer Gel Impregnated with Iron Hydroxide
Published on: June 28, 2019
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Iron amendments to reduce bioaccessible arsenic
William G Cutler1, Aly El-Kadi2, Nguyen V Hue3
1Integral Consulting Inc., 285 Century Place, Suite 190, Louisville, CO 80027, USA; Department of Geology and Geophysics, University of Hawaii at Manoa, 1680 East-west Road, Honolulu, HI 96822, USA.
Journal of Hazardous Materials
|August 13, 2014
Summary
Iron-based soil treatments effectively reduce arsenic (As) bioaccessibility on Hawaii Island, offering a cost-effective alternative to landfilling. This method sequesters arsenic (As), lowering potential human health risks from contaminated soils.
Area of Science:
- Environmental Science
- Soil Science
- Geochemistry
Background:
- Historical use of arsenical pesticides has led to elevated soil arsenic (As) levels on former sugarcane lands in Hawaii.
- Assessing human health risks and determining remediation needs involves evaluating the bioaccessible fraction of total As (AsTOT).
- In vitro bioaccessible As (AsIVBA) is a key metric for understanding potential As uptake through incidental soil ingestion.
Purpose of the Study:
- To evaluate the efficacy of ferric chloride plus lime and ferrous sulfate plus lime in reducing in vitro bioaccessible As (AsIVBA) in contaminated soils.
- To investigate the role of iron (Fe) oxyhydroxide formation in sequestering arsenic (As).
- To assess the impact of phosphate (PO4) addition on AsIVBA in treated and untreated soils.
Main Methods:
- Field plot experiments were conducted on As-contaminated soils from Hawaii.
- Two iron (Fe) sources (ferric chloride and ferrous sulfate) were applied with lime at different concentrations (0.25wt% and 0.5wt% Fe).
- In vitro bioaccessibility assays were performed over a 2-year period, with additional tests involving phosphate (PO4) amendment.
Main Results:
- Both Fe sources significantly reduced AsIVBA, with higher reductions observed at the 0.5wt% Fe dosage (59-63%) compared to 0.25wt% Fe (30-41%).
- The two Fe treatments performed similarly in reducing AsIVBA over the 2-year observation period.
- Addition of phosphate (PO4) to both treated and untreated soils resulted in a significant increase in AsIVBA, more than doubling it in some cases.
Conclusions:
- In situ application of ferrous sulfate plus lime is a cost-effective method for reducing AsIVBA in contaminated soils, estimated to be significantly cheaper than excavation and landfill disposal.
- The formation of additional Fe oxyhydroxides effectively sequesters arsenic (As), lowering its bioaccessible fraction.
- Phosphate addition should be carefully considered as it can increase AsIVBA, potentially counteracting remediation efforts.
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