Electrochemically assisted photocatalytic degradation of contaminants of emerging concern in simulated wastewater using WO3 – Elucidation of mechanisms

Abstract

In this work, the performance of a photoelectrochemical cell to degrade a mixture of contaminants of emerging concern (CECs) in distilled water and simulated wastewater effluents (SWWE) was assessed. The CECs mixture included trimethoprim (TMP), diclofenac (DFC), sulfamethoxazole (SMX) and carbamazepine (CBZ) (100 μg·L−1 each). WO3 nanoplate-like structures synthesized on fluorine tin oxide coated glass (FTO) were used as the photoanode with Pt or carbon gas diffusion electrodes (GDE) as the counter electrode. The most efficient degradation of the CECs was obtained with the WO3-GDE combination. Significant degradation of the CECs was observed under visible only radiation. Even under visible radiation, reasonable rate constants 5.67·10-3, 5.35·10-3, 2.9·10-3 and 4.35·10-3 min−1 were obtained for TMP, SMX, CBZ and DFC degradation. The degradation mechanism at the cathode and the photoanode was elucidated using a two-compartment cell, which allowed the identification of reactive species generated at each electrode. Photogenerated holes were the main responsible for CEC degradation in SWWE. With the carbon GDE, a high Faradaic efficiency (55 %) for H2O2 production was observed.