Ammonium-pillared montmorillonite-CoFe 2 O 4 composite caged in calcium alginate beads for the removal of Cs + from wastewater.

Novel and magnetic adsorbent ammonium-pillared montmorillonite-CoFe2 O4 composite caged in calcium alginate beads was prepared by using non-toxic raw materials. The morphology, magnetic properties, functional groups, and crystal structure of the compound were characterized by SEM, VSM, FT-IR and XRD. The adsorption behaviors were also investigated via adsorption experiments and response surface methodology was used to optimize the operation conditions. The beads showed high selectivity for Cs+ in the presence of Na+ and could be rapidly separated from the mixed solution under an external magnetic field. The maximum adsorption capacity was 86.46mg/g, which is higher than that of previously reported magnetic adsorbents. The adsorption kinetics and adsorption isotherms could be expressed by the pseudo-second-order and Langmuir isotherm, respectively. The relationship between a dependent variable (i.e., removal efficiency or adsorption capacity) and an independent variable (i.e., initial concentration, contact time, and adsorbent dosage) could be fitted to a quadratic second-order polynomial equation. The adsorption mechanism primarily involved ion exchange while coordination reactions also contributed.