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25. EMPIRICAL MODELS DEVELOPMENT FOR THE SORPTION OF Ni(II) ONTO CLAY by Uwadiae S.E. Volume 54 (January 2020 Issue)
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EMPIRICAL MODELS DEVELOPMENT FOR THE SORPTION OF Ni(II) ONTO CLAY

Uwadiae S.E.

Department of Chemical Engineering, Faculty of Engineering, University of Benin, PMB 1154, Benin City, Edo State, Nigeria.

Abstract

This paper examined the kinetics of nickel removal from aqueous solution by a kaolinitic clay and also developed a predictive kinetic model for it. The absorbent used was first characterized before it was used for the adsorption of Ni(II) from aqueous solution using the batch mode. After a preliminary equilibrium studies, the kinetic studies were carried out by varying the adsorbent doses from 0.2g to 1g at fixed adsorbate concentration while varying the time from 5min to 120 min. The kinetic studies were also carried out by varying by varying the metal ion concentration from 2mg/l to 8mg/l at a constant adsorbent dose while varying the time from 5 min to 120 min. The kinetic profile was modeled using pseudo-first-order model, pseudo-second-order model and Elovich model. The kinetic sorption profiles offered excellent fit with pseudo-second-order model with high coefficient of determination, R2 values of 0.9970 to 0.9990 and 0.9989 to 0.9999 when varying adsorbent dose and when varying heavy metal ion concentration respectively. Empirical models were developed to predict metal ion uptake at any time in terms of varying initial metal ion concentration and contact time, as well as for varying absorbent dose at any contact time. The developed models were validated using root mean square error (RMSE).The low RMSE values of 0.0701 and 0.00620 respectively for varying absorbent dose and contact time and for varying initial metal ion concentration and contact time show that the empirical models derived from the experimental data were able to predict the metal ion uptake at any time quite well. The empirical models developed indicate that the metal ion uptake at any contact time is higher as initial metal ion concentration but decreased with a increased adsorbent dose.

Keywords: Clay, kinetic modelling, adsorbent, adsorption kinetics

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