ISOTHERM AND KINETIC STUDIES OF Pb(II) ADSORPTION ON RAW AND MODIFIED DIATOMITE BY USING NON-LINEAR REGRESSION METHOD

摘要

This study presents the evaluation of the original diatomite (Do) and manganese oxide modified (DMn) diatomite used as adsorbents for Pb (II) removal from aqueous solution. The experimental data were fitted to the non-linear two-parameter equation of Langmuir, Freundlich, Dubinin-Radushkevich, and non-linear three-parameter equation of Redlich-Peterson, Sips and Toth Isotherms. The correlation coefficient (R2), standard error (S.E) and Chi-square (x2) values were used to select the best theoretical isotherm. Adsorption mechanism of Pb(II) ion onto the DO was explained by heterogeneous adsorption model while homogenous adsorption model was used to explain the adsorption on DMn. Also, both adsorbents were observed to comply better with the three-parameter isotherms. Pseudo first-order, pseudo second-order, Elovich and intraparticle diffusion equations were used to describe the adsorption rate of Pb(II). The experimental data were well fitted by the pseudosecond-order kinetic model. Thermodynamic parameters such as free energy (AGo), enthalpy (AHo) and entropy (ASo) showed spontaneous and endothermic in nature of adsorption for both of adsorbents.