Simultaneous immobilization of lead, cadmium and arsenic in soil by iron-manganese modified biochar

• Published in: Frontiers in environmental science 2023-10, Vol.11
• Main Authors: Yang, Zhihui, Zeng, Gai, Liu, Lin, He, Fangshu, Arinzechi, Chukwuma, Liao, Qi, Yang, Weichun, Si, Mengying
• Format: Article
• Language: English
• Subjects: arsenic; biochar; cadmium; immobilization; lead
• ISSN: 2296-665X; 2296-665X
• DOI: 10.3389/fenvs.2023.1281341

Cationic lead/cadmium and anionic arsenic exhibit opposite geochemical behaviors in soils, which makes the synchronous remediation of As, Cd, and Pb challenging. In this study, we developed an iron-manganese modified biochar (BC-Fe-Mn) that prepared from straw with iron (Fe) and manganese (Mn) loading at a pyrolysis temperature of 550 °C. After BC-Fe-Mn immobilization for 90 days, the simultaneous immobilization efficiency of Pb, Cd, and As reached 57%, 51%, and 35%, respectively. Speciation distributions shows that As transformed from specific bound state into weakly low crystallinity iron bound state. Cd transformed from carbonate fraction into Fe-Mn oxide bound fraction, and Pb transformed from carbonate fraction into residual state. During the procedure, simultaneous immobilization mechanisms might involve heavy metal morphological transformation, precipitation/co-precipitation, and surface complexation. Cd and Pb absorbed onto BC-Fe-Mn. Then the increased free iron oxides (Fe d ) reacted with the dissolved As to form iron-arsenic precipitation. The results show that BC-Fe-Mn is a promising material for the simultaneous immobilization of Pb, Cd, and As in multi-metal contaminated soil.