Efficacy of bentonite/iron-coated sand as a sediment stabilizer in controlling cadmium, lead, zinc, and arsenic release determined using the diffusive gradients in thin film technology

Abstract

In this study, we investigated the efficiency of a bentonite/iron-coated sand (B/ICS) stabilizer in reducing the mobility and accumulation of heavy metals (Pb, Cd, Zn, and As) in contaminated sediments. Bentonite is effective in the adsorption of heavy metals, while ICS is effective in the adsorption of As. When combined, the stabilizer can be applied to mixed-contaminated sediments containing both heavy metals and As. The experimental setup involved B/ICS with sediments, followed by the analysis of heavy metal accumulation using diffusive gradients in thin-film resin gels for a period of 28 days. The results obtained showed significant decreases in Pb, Cd, and Zn accumulation owing to the use of the stabilizer, particularly when its concentration was 15 % of the sediment. Conversely, As accumulation did not show a decreasing trend owing to the low selectivity of the resin gel for As. Regardless, at the end of the 28-day test period, vertical distribution analysis indicated a notable decrease in heavy metal concentrations in the stabilizer layer of the contaminated sediment. These findings indicated that B/ICS is a cost-effective and efficient stabilizer for reducing heavy metal mobility in sediments. Long-term experiments are recommended to further validate these findings and optimize the use of the stabilizer in the field.