Co-sorption of phthalate esters and Cd²⁺ on biochar-sulfhydryl modified montmorillonite composites

Developing efficient passivating sorption materials for the treatment of combined pollution by phthalate esters (PAEs) and Cd²⁺ has become a critical focus in environmental protection and soil remediation. In this study, biochar-sulfhydryl modified montmorillonite composites (BC-SHMMT) were synthesized, characterized, and evaluated for the co-sorption of PAEs (DMP, DEP) and Cd²⁺. The integration of sulfhydryl-modified montmorillonite (MMT-SH) with biochar improved the material's surface structure, enhancing both co-sorption capacity and structural stability. Molecular dynamics simulation indicated a monolayer chemical sorption of pollutants by BC-SHMMT, in alignment with the sorption theoretical model. In the co-sorption system, the coexistence of pollutants increased the adsorption of Cd²⁺ and decreased the sorption of PAEs. The smaller molecular size and higher diffusion coefficient of Cd²⁺ facilitated its pore filling and interaction with oxygen-containing functional groups of the material, leading to competition with PAEs for sorption sites. Notably, the ion exchange and complexation of Cd²⁺ adsorption by MMT-SH are pivotal in enhancing BC-SHMMT co-sorption capacity. These findings provide valuable insights into the development of eco-friendly novel materials and the improvement of co-pollution remediation efficiency.