Tetrasodium iminodisuccinate modified montmorillonite for Pb and Cd adsorption from water: Characterization and mechanism

Heavy metal pollution is a huge hazard to the water environment and modified clay adsorbents have been widely used to remove heavy metals from water. Degradable anionic chelating agents have a greater potential for the immobilization of heavy metals, so tetrasodium iminodisuccinate (IDS) was introduced to modify montmorillonite (Mt) for Pb(II) and Cd(II) adsorption from water in this study. IDS was bound with Mt by sonication, heating, and acidity to form IDS-Mt, and characterized by XRD, FT-IR, SEM, and zeta potential analyzer. The batch adsorption experiments revealed that IDS-Mt5 had excellent adsorption capacity of Pb(II) and Cd(II) up to 214.73 mg/L and 104.07 mg/L, respectively. The adsorption process of IDS-Mt on Pb(II) and Cd(II) was consistent with the Sips model and PSO model, indicating that the adsorption was heterogeneous and chemical. The adsorption capacities of IDS-Mt in the second cycle remained above 76 % for Pb(II) and 69 % for Cd(II) of the initial ones, respectively. IDS was immobilized on the interlayer and edge surfaces of Mt through interactions or forming hydrogen bonds facilitated by ultrasonic under acidic heating conditions. Pb(II) and Cd(II) were immobilized by IDS-Mt through cation exchange, negative charge attraction at the edge surface, and IDS chelation. IDS-Mt was an excellent adsorbent with strong dispersibility and swelling properties for Pb(II) and Cd(II) removal from contaminated water. This study provides a new solution for the anionic modification of Mt and a new material for the treatment of heavy metal wastewater.