A study published in Environmental Technology & Innovation by Xin Teng and colleagues explores a novel approach to address the simultaneous removal of cadmium (Cd(II)) and selenite (Se(IV)) from contaminated water and soil. By impregnating sulfidated nanoscale zerovalent iron (SNZVI) into shrimp shell-derived biocharBiochar is a carbon-rich material created from biomass decomposition in low-oxygen conditions. It has important applications in environmental remediation, soil improvement, agriculture, carbon sequestration, energy storage, and sustainable materials, promoting efficiency and reducing waste in various contexts while addressing climate change challenges. More, the researchers created a material with dual functionality to target these contaminants, which often coexist and have opposite charges.

The optimized composite (SNZVI/BC0.3) demonstrated adsorption capacities of 128.4 mg/g for Cd(II) and 282.8 mg/g for Se(IV) in mixed systems, surpassing prior technologies. Additionally, it removed over 97% of Se(IV) and 99% of Cd(II) from real-world water samples with contaminant levels of 1 mg/L. The mechanism involves the reduction of Se(IV) by Fe(0) and the substitution of Fe(II) in FeS by Cd(II). Synergistic effects were observed, where immobilized Cd(II) facilitated further adsorption of Se(IV).

Field applications showed the composite reduced bioavailable Cd and Se in soil by 63% and 44%, respectively, under waterlogged conditions. However, its performance decreased over four reuse cycles due to material degradation.

This innovative approach highlights the potential of combining biochar with nanoscale materials for efficient remediation of complex contaminant mixtures in water and soil, offering an eco-friendly solution for environmental cleanup.

SOURCE: Teng, et al (2025) Simultaneous sequestration of Cd(II) and Se(IV) by sulfidated nanoscale zerovalent iron impregnated in shrimp shell-derived biochar: Mechanism and site energy distribution analysis. Environmental Technology & Innovation. https://doi.org/10.1016/j.eti.2025.104032