ADSORPTION STUDIES FOR THE REMOVAL OF CU(II) AND PB(II) FROM AQUEOUS SOLUTION BY LOCAL ADSORBENT USING NONLINEAR REGRESSION METHODS
Uwadiae, S. E.
1Department of Chemical Engineering
Afe Babalola University, Ado-Ekiti, Ekiti state.
Email: suwadiae@yahoo.com
ABSTRACT
The sorption of two divalent metal ions – copper and lead – from aqueous solution onto Ikpoba clay in single component systems has been studied. Batch adsorption study for the clay fraction was conducted at ambient temperature, using <0.02mm particle sizes. The experimental data have been analysed using the Langmuir, Freundlich, Redlich-Peterson, Toth and Sips isotherm models. In order to determine the best fit isotherm for each system, five error analysis methods were used to evaluate the data: hybrid fractional error function (HYBRID), Marquardt’s percent standard deviation (MPSD), average relative error (ARE), sum of the errors squared (ERRSQ) and sum of the absolute errors (EABS). However, the sum of normalized error (SNE) was further employed in order to have a better comparison between the error functions sets for the isotherm models. The error values indicated that the Sips isotherm was able to provide the best quality of fit for all the experimental data, over the concentration range (3-6 mg/L) studied for Cu(II) with error values of 13.9609 , 0.3104, 0.0025, 2.9965, 0.1220 and 0.2111 for ARE, EABS, ERRSQ, HYBRID, MPSD and SNE respectively; while Toth isotherm gave the best quality of fit for all the experimental data, over the concentration range (20-40 mg/L) studied for Pb(II) with error values of 19.9202, 0.4070, 0.0469, 6.0984, 0.2316, 0.33072 for ARE, EABS, ERRSQ, HYBRID, MPSD and SNE respectively.
Keywords: Isotherms, Error-functions, Sorption, nonlinear regression, heavy metal
