Degradation of contaminants of emerging concern in a secondary effluent using synthesized MOF-derived photoanodes: A comparative study between photo-, electro- and photoelectrocatalysis

Abstract

Three metal-organic framework (MOF)-based photoanodes were prepared by deposition on TiO₂ nanotubes using Ti as substrate (Ti/TiO₂NT): i) Ti/TiO₂NT-Au@ZIF-8, ii) Ti/TiO₂NT-Ru₃(BTC)₂, iii) Ti/TiO₂NT-UiO-66(Zr)NH₂. These photoanodes were characterized by FEG-SEM, EDX and DRX. The analyses showed a successful modification and a high homogeneity of the different MOFs on the Ti/TiO₂NT surface. The photoanodes were studied in the degradation of Contaminants of Emerging Concern (CECs) in a spiked secondary effluent from a Municipal Wastewater Treatment Plant (MWWTP). Sodium diclofenac (DCF), sulfamethazine (SMT) and carbamazepine (CBZ) were used as CECs at low concentration (200 μg/L each CEC). The samples were preconcentrated using Solid Phase Extraction (SPE) and analyzed by a HPLC-DAD system. The MOF-based photoanodes exhibited a high photoelectrochemical (PEC) activity towards the oxidation of CECs, achieving up to 50%, 70% and 80% of removal using Ti/TiO₂NT-Au@ZIF-8, Ti/TiO₂NT-UiO-66(Zr)NH₂, Ti/TiO₂NT-Ru₃(BTC), respectively. The influence of the generation of hydroxyl radical was then studied. The results indicate that PEC degradation using Ti/TiO₂NT-Ru₃(BTC)₂ and Ti/TiO₂NT-UiO-66(Zr)NH₂ is more affected by the concentration of the radical.

Keywords: Contaminants of emerging concern; Hydroxyl radical; MOF-Derived photoanode; Photoelectrochemical degradation; Secondary effluent.