Adsorption of cadmium onto Al(13)-pillared acid-activated montmorillonite

The optimal preparation conditions for Al(13)-pillared acid-activated Na(+)-montmorillonite (Al(13)-PAAMt) were (1) an acid-activated Na(+)-montmorillonite (Na(+)-Mt) solution of pH 3.0, (2) a OH(-)/Al(3+) molar ratio of 2.4 and (3) Al(3+)/Na(+)-Mt ratio of 1.0 mmol g(-1). The effects of OH(-)/Al(3+) and Al(3+)/Na(+)-Mt ratios on the adsorption of Cd(2+) onto Al(13)-PAAMt were studied. A comparison of the adsorption of Cd(2+) onto Al(13)-PAAMt, Al(13)-pillared Na(+)-montmorillonite (Al(13)-PMt) and Na(+)-Mt suggested that Al(13)-PAAMt had higher adsorption affinity for Cd(2+) 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.