Sorption of Cd2+ on mercapto and amino functionalized palygorskite

Sorption of Cd2+ on PAL, PAL-SH and PAL-NH2 involved different mechanisms. For pristine palygorskite, Cd2+ reacted with surface hydroxyl groups to form surface complexation; for mercapto functionalized palygorskite, the complexation of Cd2+ with mercapto groups existed in addition to the complexation with surface hydroxyl groups; for amino functionalized palygorskite, surface precipitation of Cd2+ with OH and CO2 to form CdCO3 played an important role in the sorption process except complexation with amino and hydroxyl groups.