Development of a hybrid bifunctional rotating drum electrode system for the enhanced oxidation of ciprofloxacin: An integrated photoelectrocatalysis and photo-electro-Fenton processes

Mismanaged antibiotics ending up in aquatic environment due to inadequate conventional treatment urges the need to develop powerful advanced oxidation techniques. In this study, hybrid bifunctional rotating drum reactor (BRDR) has been developed and its potency in enhancing the degradation of ciprofloxacin has been demonstrated. BRDR is a hybrid reactor that integrates - photoelectrocatalysis (PEC) and photo-electro-Fenton (PEF) processes with UVA irradiation. It consists of MoS2-TiO2-coated carbon cloth as anode and Ferrocene-functionalized graphene-coated graphite felt as cathode. BRDR system significantly improved the removal efficiency (99.9 %) as compared to individual efficiencies of PEC (71 %) and PEF (78.8 %) processes. An increase in electrode rotation speed significantly enhanced the removal without external aeration (0.059 min(-1) for 60 rpm). Maximum removal rate was achieved at pH 3 (0.061 min(-1)) followed by 7 (0.040 min(-1)) and 9 (0.020 min(-1)). The increase in applied potential from open circuit voltage to 1.5 V improved the removal rate from 0.005 min(-1) to 0.040 min(-1). The mechanism of reactive oxygen species production in BRDR system is elaborated. BRDR is demonstrated to be cleaner treatment system which excludes the external chemical addition, aeration, and sludge formation.