Dual Ions Neutralized and Stabilized Red Mud for Chromium(VI) Polluted Soil Remediation

作者：Dazhong Yang, Zheting Chu, Xuezhen Feng, Qiuyue Ge, Ranhao Wang, Juan Zhang, Shangying Li, Renji Zheng, Wenfei Wei, Shuping Yi, Hong Chen · 发表于：ACS ES&T Engineering · 年份：2022 · DOI：10.1021/acsestengg.1c00420 · 被引用次数：21 · 研究领域：Bauxite Residue and Utilization、Arsenic contamination and mitigation、Environmental remediation with nanomaterials

Both alkaline heavy metal (HM) contaminated red mud (RM) recycling and Cr(VI) polluted soil remediation are severe hazardous environmental problems. Herein, we developed a novel integrated approach to neutralize and stabilize the hazardous RM via the introduction of Ca 2+ and Cl – dual ions. When 3% CaCl 2 ·2H 2 O is added, the pH of RM is reduced from 11.0 to 8.9, and the Pb, Cr, Zn, Cu, and As leaching concentrations from RM are suppressed lower than the environmental standards of China and the World Health Organization (Pb, Cr, Zn, Cu < 0.50 mg/L; As < 10 μg/L). Detailed mechanism studies reveal that the pH neutralization is attributed to the novel OH – flocculation effect ascribing to Ca 2+ charge neutralization and Cl – promoted proton neutralization. Furthermore, as the pH decreases, the HM adsorption capacity of RM is enhanced, achieving stable HM immobilization. The treated RM can be further employed to remediate Cr(VI) contaminated soil (Cr concentration 570 ppm; treated RM weight percentage in soil 5.0%), which can suppress 56.0% Cr mobility in soil and 68.4% bioaccumulated Cr in the harvested vegetables. Overall, this work demonstrates an ecofriendly “waste-to-soil remediation” strategy to solve both the solid waste and soil pollution problems.