Magnetic Sulfide–Modified MFe₂O₄/Montmorillonite (M=Fe, Zn) for Efficient Sorption of Cd(II)

Modified montmorillonite has been widely used for the adsorption of heavy metal Cd(II), but there are few studies on the preparation of adsorbents that are easy to recover and can be efficiently adsorbed. In this paper, magnetic S-MFe₂O₄/MMT (M=Fe, Zn) composites with huge specific surface multi-class functional groups were prepared on montmorillonite loaded with Zn and S doubly-modified Fe₃O₄ to explore its performance in Cd(II)-contamination, to reveal the removal mechanism of Cd contamination, and to evaluate the stabilization effect of S-MFe₂O₄/MMT (M=Fe, Zn). The results showed that the optimum adsorption pH of S-ZnFe₂O₄/MMT for single Cd(II) was 6.0, the maximum adsorption was 56.68 mg·g⁻¹, and the adsorption process was by the quasi-secondary kinetic model and Langmuir isothermal adsorption model. In addition, the effects of the coexistence of Cr³⁺, Ni²⁺, and Pb²⁺ on the adsorption performance of Cd(II) were not significant, and the adsorption of Cd(II) remained above 55.70 mg·g⁻¹ and showed better adsorption of Pb²⁺ (98.20 mg·g⁻¹) and Cr³⁺ (92.78 mg·g⁻¹). In conclusion, the composites can be used as an effective remediation reagent for Cd(II)-contaminated soil.