Insights in the Aqueous and Adsorbed Photocatalytic Degradation of Carbamazepine by a Biosourced Composite: Kinetics, Mechanisms and DFT Calculations

Abstract

Although the degradation of carbamazepine (CBZ) in the aqueous phase was widely studied for a better comprehension of its photocatalytic behavior in the aqueous solution, the knowledge about its photodegradation adsorbed on solid surfaces is yet very limited. In this work, the combination of two processes (adsorption and photocatalysis) has been applied for the degradation of CBZ adsorbed on TiO2 and activated carbon AC/TiO2 and aqueous phase. The degradation efficiency of CBZ could reach 100%, and 99% in CBZ dissolved and adsorbed parts, respectively. Moreover, the CBZ mineralization starts at 4 h of irradiation. Hydroxy radical (·OH) has an essential role in CBZ degradation, and It accompanies a synergistic effect of the photogenerated hole (h+) and oxygen active species during the reaction. Thereafter, the transformation products and possible degradation pathways of CBZ were identified by LC/MS-Qtof. Density functional theory calculation successfully predicts the degradation mechanism of CBZ molecule by means of Fukui indexes, including the ring hydroxylation, photocyclization, C–C and C–N bond cleavage processes.