Sulfur-Doped Biochar Stabilized Harmful Trace Elements in FGD Sludge to Achieve Cyclic Utilization for Landfill Soil Remediation

Trace elements in FGD sludge from four power plants were stabilized with H₂S-modified biochar. A TCLP experiment demonstrated that the incorporation of 5% biochar proved to be the most efficacious method for stabilizing trace elements. The migration capacity of harmful elements is mitigated by the mechanisms of physical adsorption and the action of surface R-SO₃H groups. The average effective fractions of Hg, As, Pb, Cd, Cr, Ni, Cu, Zn, and Sb in the FGD sludge from four power plants after stabilization decreased by 28.7, 3.2, 24.8, 11.2, 8.2, 15.3, 16.3, 17.9, and 0.3%, respectively. Hg was decreased from 61.2 μg/kg and 2.3 mg/kg to 6.6 μg/kg and 1.5 mg/kg in soil and corns, respectively. As, Se, Pb, Cd, Cr, Ni, Cu, Zn, and Sb were decreased by 0.3–89.2% and 2.1–41.4% in the soil and corn, respectively. The germination rate of corn in soil remediated with modified biochar rose from 29.2 to 50.0%.