Adsorption of phenol, phosphate and Cd(II) by inorganic-organic montmorillonites: A comparative study of single and multiple solute

Inorganic-organic montmorillonites (IOMts) obtained by modifying polyhydroxy-aluminum (Al13)-pillared montmorillonite (AlPMt) with the cationic surfactant (C16) and zwtterionic surfactant (Z16) were investigated with the aim to remove phenol, phosphate and Cd(II) simultaneously. The structures of IOMts prepared using different surfactant doses (0.4 and 1.0 CEC) strongly depended on the types and doses of the surfactants. The Al13 contents of C16 modified AlPMts (C-AlPMts) decreased with increasing C16 loading while that of Z16 modified AlPMt (Z-AlPMts) did not. In the single adsorption system, all IOMts could efficiently remove phenol and phosphate, but not Cd(II). IOMts, however, could efficiently remove all three contaminants simultaneously in the multi-contaminant adsorption system. The adsorptions of phenol on IOMts were not affected by the other two inorganic components and vice versa. Whereas the adsorptions of phosphate and Cd(II) were significantly enhanced in the multi-contaminant system, and the adsorption of one increased with increasing initial concentration of the other one, especially the adsorption of Cd(II). The enhancements of adsorption of phosphate and Cd(II) on the IOMts with higher Al13 content were much larger than that on IOMts with lower Al13 content. The adsorption mechanism for phosphate and Cd(II) uptake in the multi-contaminant system possible involve the formation of phosphate-bridged ternary complexes