The antiepileptic drug, carbamazepine (CBZ) is one of the most detected pharmaceutical and personal care products and an aromatic drug that has been under study due to its toxicity and recent growing concentration in wastewater effluents. Currently, CBZ has very low removal efficiencies (&lt;10%) in conventional wastewater plants. Here, this study focuses on the visible light induced electrochemical transformation kinetics and mechanistic pathways of the photoelectrocatalytic oxidized intermediates of CBZ in a carbon dot-based photoelectrochemical cell (CDPEC). As an essential component of a working photoanode for photocatalytic CBZ degradation, the photoanode incorporates 2,2′-(ethylenedioxy)bis(ethylamine) carbon “quantum” dots (EDA-CDTs) on a nanorod structured TiO2 electrode. The degradation experiment was carried out under aerobic conditions at room temperature in a CDPEC in the presence of NaCl and Na2SO4. This photoelectrocatalytic process facilitates an advanced oxidation process by forming reactive species via reaction with hydroxyl radicals (or reactive oxygen species) generated from high-energy hole-electron interaction at the interface of the electrodes. As a result, this process forms free chlorine species (HOCl/ClO-), which interacts with CBZ and degrades it into intermediates and other byproducts. Moreover, the degradation products were analyzed using triple-quadrupole LC-MS/MS to provide structures for the mechanistic pathway. To elucidate the mechanistic pathways of the oxidative degradation products, the pathway was then analyzed and confirmed for each intermediate step via molecular simulation techniques from CBZ to the known intermediate acridine. These simulations were able to help further understand the kinetic and mechanistic breakdown of CBZ via visible light and the radical present in the photoelectrochemical cell. The use of an EDA-CDT photoanode-based photoelectrochemical cell system with visible light utilizing hole oxidation through reactive chlorine radicals provides a more versatile application for water remediation.

Photoelectrochemical degradation kinetics and pathways of the recalcitrant pharmaceutical compound carbamazepine

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