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 4 ·7H 2 O treatment process. The process was able to rapidly reduce the TCLP-based leachability of Pb from 12.74 to 0.1 mg L −1 and As from 2.704 to 0.002 mg L −1 (MW power = 800 W, Irradiation time = 20 min, and FeSO 4 ·7H 2 O = 4 wt%). The effects of FeSO 4 ·7H 2 O 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 −1 , respectively. The microwave irradiation promoted the formation of insoluble PbSO 4 (s) and Fe 3 (AsO 4 ) 2 ·8H 2 O(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.