Enhancing Coimmobilization Capacity of Schwertmannite for Arsenic and Cadmium through pH Elevation after Chemical Oxidation
Xiaomeng Wang, Lijie Wang, Jingran Fu, Yiming Zhang, Yan Dong, Guanyu Zheng, Lixiang Zhou
Abstract
Schwertmannite (Sch) is a promising environmental functional material for remediation of arsenic pollution, particularly arsenite [As(III)], due to its unique adsorption mechanism. However, its application in metal–metalloid cocontamination is greatly limited by its ineffective immobilization of cationic metals. In this study, a preparation method of chemical oxidation–pH elevation was proposed to optimize the immobilization capacity of schwertmannite for As and cadmium [Cd(II)], which referred to promoting solution pH to neutral conditions after FeSO 4 –H 2 O 2 chemical oxidation. The resultant schwertmannite mixture (Sch-M) had a slightly increased Fe content (by 14.2–17.7%) and a reduced sulfate content (by 24.5–42.1%) compared to Sch. Sch-M displayed stronger mineral phase stability under anaerobic Fe(II)-catalyzed condition. The adsorption capacity of Sch-M for As(III) was basically consistent with that of Sch (172.9–211.3 vs 196.5 mg/g) and reached 19.7–22.4 mg/g for Cd(II) at pH 6.5. Sch-M performed better stabilization effects for metals and metalloids in a contaminated soil than zerovalent iron. In addition, its passivation ability was resistant to acidic conditions (pH 2.6). The practical application of the Sch-based environmental functional material in the remediation of metal(loid)-contaminated soils is worthy of in-depth study.