Equilibria and Kinetic Studies on the Adsorption of Cadmium onto Cameroonian Wetland Clays
C. M. Kede *
Department of Chemistry, Tshwane University of Technology, P.O. Box 56208, 0007 Arcadia, Pretoria, Republic of South Africa and Department of Chemistry, Faculty of Science, University of Douala, 00(237)3340 75 69; PO Box 24175 Douala, Cameroon.
MA Etoh
Department of Chemistry, Faculty of Science, University of Douala, 00(237)3340 75 69; PO Box 24175 Douala, Cameroon.
P. P. Ndibewu
Department of Chemistry, Tshwane University of Technology, P.O. Box 56208, 0007 Arcadia, Pretoria, Republic of South Africa.
H. M. Ngomo
Department of Chemistry, Faculty of Science, University of Yaoundé I, PO Box 812 Yaoundé, Cameroon.
P. M. Ghogomu
Department of Chemistry, Faculty of Science, University of Yaoundé I, PO Box 812 Yaoundé, Cameroon.
*Author to whom correspondence should be addressed.
Abstract
The possible use of clay (AL2Si3O5(OH)4, locally mined (Make pe, Cameroon), as an adsorbent, for the removal of cadmium from wastewater was investigated. Spectroscopic studies including FTIR, elemental analysis (EA), XRPD, and SEM were used for its characterization. The effect of different variables, namely: concentration of metal ions, pH and time of interaction were studied. The adsorptive property of clay was tested using Cd(II) as the model adsorbate. Equilibrium data was examined using a comparison of linear isotherm models. The adsorption behavior was well described by the linear Langmuir isotherm model, showing a monolayer adsorption capacity for Cd(II). The kinetic rates were modeled by using the Lagergren-first-order, pseudo-second-order and intra particle model. The pseudo-second-order model was found to explain the adsorption kinetics most effectively. It was also found that the pore diffusion played an important role in the adsorption and intraparticle diffusion was the rate-limiting step during the first 30 min. of interaction.
Keywords: Adsorption, kinetic, equilibrium, wetland clays, cadmium.