Heavy-metal uptake by a high cation-exchange-capacity montmorillonite: the role of permanent charge sites

A High Cation Exchange Capacity (HCM) montmorillonite clay has been prepared by acetate
treatment of Zenith clay. The HCM has been evaluated for metal-uptake from aqueous solutions.
The present data show that the cation exchange sites can play a significant role in the adsorption of
metals in smectite clays. A theoretical analysis scheme has been developed which shows that
permanent-charge sites can become dominant in metal-uptake by clays. In addition, it was shown
that the permanent charge can influence the ionic-strength sensitivity of the Point of Zero Charge of
the clay.