Removal of sulfamethazine by a flow-Fenton reactor with H2O2 supplied with a two-compartment electrochemical generator

Abstract

A novel continuous-flow H2O2 electrochemical generator using a natural air diffusion electrode (NADE) as the cathode was designed and the two compartments of the generator were separated by a cation exchange membrane. The reactor did not require aeration, which saved aeration energy consumption. The reactor showed good performance in generating H2O2 up to 50.8 mg/h/cm2 with the energy consumption of 25.2 kWh/kg H2O2, and maintained a high current efficiency of about 70–94% in the current density range of 20 to 100 mA/cm2. The yield of H2O2 and current efficiency remained high and stable in a wide pH range of 3 ∼ 9. H2O2 produced in the generator was delivered to a flow-Fenton reactor for the occurrence of the Fenton reaction and the degradation of sulfamethazine (SMT), which avoided the problem of excessive generation and ineffective consumption of H2O2 in the electro-Fenton process and improved the utilization rate of H2O2. Moreover, due to the introduction of H2O2 solution with low pH to the flow-Fenton reactor, the pH of the working solution did not need adjustment. The flow-Fenton process achieved 99% of SMT removal, 90% of H2O2 utilization rate, and 54% of TOC removal within 20 min under the optimum conditions. The degradation of several other contaminants (2,4-dichlorophenoxyacetic acid, tetracycline and carbamazepine) was investigated and all of the removals were maintained above 97%. The study is promising for the practical electrochemical production of H2O2 and application of flow-Fenton for contaminants degradation.