Isotherm studies of lead(II), manganese(II), and cadmium(II) adsorption by Nigerian bentonite clay in single and multimetal solutions

Abstract

ABSTRACTThis study was aimed at evaluating the isotherm of lead(II), manganese(II), and cadmium(II) adsorption in single and multimetal solutions using Nigerian bentonite. The natural and calcined clays were characterized for specific surface area, surface morphology, elemental composition, and cation exchange capacity (CEC). The adsorption data were analyzed and interpreted using isotherm models. The natural bentonite exhibits a specific surface area of 23.5 m2/g and a CEC value of 47.7 mEq/100 g and displays a higher adsorption capacity of all heavy metals in both single and multimetal solutions than the calcined bentonite. The removal of lead(II) by natural bentonite in single-component system is 0.0448 mmol/g. The order of selectivity is lead(II) > cadmium(II) > manganese(II). Result also shows that both clays demonstrate a preferable adsorption toward lead(II). Lead(II) adsorption is less affected by the presence of counter cations in multimetal solution. The adsorption of heavy metals onto Dijah-Monkin bentonite is site selective and site specific, and the adsorption data are well presented by the Langmuir model. The CEC could be the primary mechanism for the uptake of heavy metals, and the removal capacity was shown to depend on the ionic radius of metal ions.