Microwave-enhanced simultaneous immobilization of lead and arsenic in a field soil using ferrous sulfate.

Remediation of soil contaminated by mixed heavy metals and metalloids has been a major challenge in the global environmental field. To address this critical issue, we tested a new technology for simultaneous immobilization of lead (Pb) and arsenic (As) in a field contaminated soil using a microwave-assisted FeSO·7HO treatment process. The process was able to rapidly reduce the TCLP-based leachability of Pb from 12.74 to 0.1 mg L and As from 2.704 to 0.002 mg L (MW power = 800 W, Irradiation time = 20 min, and FeSO·7HO = 4 wt%). The effects of FeSO·7HO dosage, microwave power, and irradiation time were determined and optimized. After 365 days of curing under atmospheric conditions, the TCLP-leached concentration of Pb and As in the treated soil remained below the regulatory limits of 0.1 and 0.002 mg L, respectively. The microwave irradiation promoted the formation of insoluble PbSO(s) and Fe(AsO)·8HO(s), resulting in the long-term stability of Pb and As in the soil. The technology offers an effective alternative for remediation of Pb- and/or As-contaminated soil and groundwater.