Isotherm Modeling on the Equilibrium Sorption of Cadmium (II) from Solution by Agbani Clay

Abstract

The main objective of this study was to remove Cadmium(II) ions from aqueous solution by adsorption unto Agbani clay as a low-cost adsorbent. The clay was used without chemical modification or treatment in order to maintain a low process cost. The effect of pH, initial Cadmium ion concentration and time were determined using batch adsorption technique. Maximum adsorption was recorded at a pH of 5.0 and equilibrium sorption was achieved within 50 minutes of the process. Equilibrium isotherm models applied showed the Freundlich isotherm model with the best regression coefficient R 2 of 0.9907, followed by the Temkin isotherm, (0.9220) and the least value was obtained with the Dubinin-Radushkevich, (0.8159) and Langmuir isotherm, (0.8158). The Langmuir isotherm constant (b) and the Freundlich constant (n) indicated a high affinity of Agbani clay for Cadmium(II) ions. A chemical adsorption process was indicated by the value of the apparent energy of adsorption (9.13KJ/mol) obtained from the Dubinin- Radushkevich isotherm. The experimental results indicated the potential of Agbani clay as a low-cost adsorbent for cadmium removal from industrial wastewaters.