Adsorption of cadmium onto Al13-pillared acid-activated montmorillonite

The optimal preparation conditions for Al13-pillared acid-activated Na+-montmorillonite (Al13-PAAMt) were (1) an acid-activated Na+-montmorillonite (Na+-Mt) solution of pH 3.0, (2) a OH−/Al3+ molar ratio of 2.4 and (3) Al3+/Na+-Mt ratio of 1.0 mmol g−1. The effects of OH−/Al3+ and Al3+/Na+-Mt ratios on the adsorption of Cd2+ onto Al13-PAAMt were studied. A comparison of the adsorption of Cd2+ onto Al13-PAAMt, Al13-pillared Na+-montmorillonite (Al13-PMt) and Na+-Mt suggested that Al13-PAAMt had higher adsorption affinity for Cd2+ than the other two adsorbents. A pseudo-second-order model described the adsorption kinetics well. Cadmium adsorption followed the Langmuir two-site equation, while desorption was hysteretic.