Plumbojarosite formation in contaminated soil to mitigate childhood exposure to lead, arsenic and antimony

Highlights: • Novel microwave assisted lead (Pb) immobilizing method developed using Fe₂(SO₄)_3. • USEPA Method 1340 showed that Pb bioaccessibility was reduced by 77–97%. • Pb accumulation in femur, liver and kidneys was reduced between 73% and 93% in mice. • XAS showed a 72–100% conversion of Pb to plumbojarosite in treated soil. • This technique also reduced arsenic and antimony bioavailability during treatment. In this study, a novel method for lead (Pb) immobilization was developed in contaminated soils using iron (III) (Fe³⁺) in conjunction with 0.05 M H₂SO₄. During method optimization, a range of microwave treatment times, solid to solution ratios, and Fe₂(SO₄)₃/H₂SO₄ concentrations were assessed using a mining/smelting impacted soil (BHK2, Pb: 3031 mg/kg), followed by treatment of additional Pb contaminated soils (PP, Pb: 1506 mg/kg, G10, Pb: 2454 mg/kg and SoFC-1, Pb: 6340 mg/kg) using the optimized method. Pb bioaccessibility was assessed using USEPA Method 1340, with Pb speciation determined by X-ray Absorption (XAS) spectroscopy. Treatment efficacy was also validated using an in vivo mouse assay, where Pb accumulation in femur, kidney and liver was assessed to confirm in vitro bioaccessibility outcomes. Results showed that Pb bioaccessibility could be reduced by 77.4–97.0% following treatment of soil with Fe₂(SO₄)₃ (0.4–1.0 M), H₂SO₄ (0.05 M) at 150 °C for 60 min in a closed microwave system. Results of bioavailability assessment demonstrated treatment effect ratio of 0.06–0.07 in femur, 0.06–0.27 in kidney and 0.06–0.11 in liver (bioavailability reduction between 73% and 93%). Formation of plumbojarosite in treated soils was confirmed by XAS analysis.