Effects of temperature on adsorption and oxidative degradation of bisphenol A in an acid-treated iron-amended granular activated carbon

The present study suggests a combined adsorption and Fenton oxidation using an acid-treated Fe-amended granular activated carbon (Fe-GAC) for effective removal of bisphenol A in water. When the Fe-GAC adsorbs, and is saturated with BPA in water, Fenton oxidation of BPA occurs in the BPA-spent Fe-GAC for regeneration of the GAC. Particularly this study showed temperature as an effective mean to enhance adsorption, desorption, diffusion and Fenton oxidation associated with the adsorption and Fenton oxidation of BPA on the Fe-GAC. The adsorption rates of BPA onto the Fe-GAC were enhanced with increasing temperature mainly due to increase in diffusion of BPA. The estimated thermodynamic parameters associated with adsorption of BPA indicated that the adsorption of BPA onto the Fe-GAC was a spontaneous, exothermic and physical adsorption process. On the other hand, the molar ratio of [H2O2]:[BPA] (36-108 H2O2/mol BPA) in the Fenton oxidation of the BPA-spent Fe-GAC led to 91-99% removal of BPA with negligible aromatic products and some soluble organic acids. The oxidation rates of BPA and H2O2 during the Fenton oxidation of the BPA-spent Fe-GAC were drastically enhanced by the factor of 2.5 and 5 when the reaction temperature increased from 293 to 331 K, respectively. The comparative analysis of temperature-dependent enhancement in diffusion, desorption and oxidation rates of BPA in Fe-GAC indicated that the BPA oxidation in the Fe-GAC is mainly controlled by diffusive transport of BPA from the Fe-GAC. Besides, the Thiele-modulus analysis clearly supported more significant pore diffusion limitation of H2O2 in the Fe-GAC with increasing temperature and the Fe-GAC particle size.