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Adsorption of arsenate from aqueous solution by ferric oxide-impregnated Dowex Marathon MSA anion exchange resin: application of non-linear isotherm modeling and thermodynamic studies

Tandorn, Sujitra, Arqueropanyo, Orn-anong, Naksata, Wimol, Sooksamiti, Ponlayuth, Chaisri, Ingon
Environmental earth sciences 2019 v.78 no.5 pp. 136
Gibbs free energy, adsorbents, adsorption, anion exchange resins, aqueous solutions, arsenates, arsenic, endothermy, enthalpy, entropy, equations, models, pH, regression analysis, sorption isotherms, temperature
The characteristic of adsorption of As(V) onto ferric oxide-impregnated anion resin Dowex marathon MSA (FO-Dowex) was investigated. Batch adsorption experiment was studied as a function of pH, contact time, initial As(V) concentration, and temperature. The results revealed that the adsorption of As(V) onto FO-Dowex was highly pH-dependent and that the equilibrium time was attained within 360 min. Two-parameter equations (Langmuir, Freundlich, and Temkin) and three-parameter equations (Redlich–Peterson and Sips) isotherm models were used for modeling the experimental data for As(V) adsorption onto FO-Dowex at different temperatures through the non-linear regression method. The goodness of fit of the isotherm model to the experimental data was evaluated by comparing the statistical values of the coefficient of determination (R²), Chi-square (χ²) and the root mean square error (RMSE). From the isotherm analysis, the equilibrium data of As(V) adsorption onto FO-Dowex were found to be in good agreement with the Redlich–Peterson, Sips, and Langmuir isotherm model, based on the higher R² value and the lower values of χ² and RMSE as compared to other isotherm models. Furthermore, the calculation of thermodynamic parameters such as Gibbs free energy change (ΔG°), enthalpy change (ΔH°), and entropy change (ΔS°) revealed that the adsorption process was feasible, spontaneous, and endothermic in nature. All the results suggested that FO-Dowex could be used an effective and potential adsorbent for the removal of As(V) from aqueous solutions.