COMPARISON OF METHYLENE BLUE ADSORPTION PERFORMANCE ON NATURAL, THERMAL AND ACID MODIFIED KAOLIN: ISOTHERM, KINETICS AND THERMODYNAMICS STUDIES

摘要

Dyes in the industrial wastewaters such as textile, food and cosmetic are the one of major water pollution source. In this study natural, thermal and acid modified kaolin have been utilized as adsorbent for the removal of methylene blue (MB) which is one of the widely used dye in the industry, from aqueous solution within a batch process. Adsorption experiments were performed at three different temperatures (298, 308, 318K). Based on the experimental data Freundlich isotherm model better than the Langmuir model. Freundlich model coefficients increase as the temperature increases, indicating that adsorption is favorable at higher temperature. The kinetic data were analyzed using pseudo first order and pseudo second order models. Adsorption of the MB on kaolin at the different conditions was best fit the pseudo second order model. Kinetic constants are closer to the both temperatures and initial concentrations and qe values are increases with increasing concentration of MB. The values of activation parameters such as free energy (?G), enthalpy (?H) and entropy (?S) were determined. Thermodynamic parameters indicates that the adsorption process is physisorption, endothermic and increased randomness at the solid-solute interface with the high affinity of the kaolin for the MB. Initial dye concentration increases from 25 to 75 mg/L, the adsorption capacity of dye onto natural, thermal modified and acid modified kaolin from 5.03 to 20.29 mg/g, 6.66 to 23.89 mg/g and 7.16 to 25.57 mg/g, respectively. It was also found that acid modified kaolin has a higher adsorption capacity compared to that of natural or thermal kaolin. The results indicate that kaolin could be interesting alternative material with respect to more costly adsorbents used for dye removal.