Highly efficient electrochemical dechlorination of florfenicol by an ultrathin molybdenum disulfide cathode

Abstract The efficient elimination of biotoxicity of halogenated antibiotics by electrochemical dehalogenation pretreatment is required by a subsequent biochemical treatment process. Molybdenum disulfide (MoS2) has been applied as an efficient catalyst for the hydrogen evolution and water splitting, without any investigation in electrochemical dehalogenation, particularly under complex environmental conditions. In this study, ultrathin MoS2 nanosheets are fabricated via a simple one-step hydrothermal process, and proved as a promising catalyst for enhancing electrochemical dehalogenation of halogenated antibiotics of a chlorinated antibiotic florfenicol (FLO) under relevant environmental conditions. Results showed that the reaction rate constant of the ultrathin MoS2 electrode (0.0135 min−1) was 4.1- and 28- fold higher than those of commercial MoS2 and bare carbon paper, respectively, and the biotoxicity of treated effluent could almost be neglected. Free radical scavenging experiments and electrochemical performance test suggested that the dechlorination of FLO on ultrathin MoS2 electrode was synergistically accomplished via the direct electron transfer and indirect reduction of active H*. Environmental conditions, namely, dissolved oxygen and humic acid had only a slight effect on the dechlorination efficiency. Electrochemical dechlorination of FLO was a gradual dechlorination process and FLO-2Cl (representing the removal of two chlorine atoms from FLO) was the final main product. Besides, the ultrathin MoS2 electrode retained a good stability and the energy consumption of the ultrathin MoS2 cathode at −1.2 V was 0.02643 kWh g−1, more than those of commercial MoS2 cathode and bare carbon paper. This study develops a new application of noble-metal-free electrode material for electrochemical dechlorination in wastewater.