A Trickle Bed Electrochemical Reactor for Generation of Hydrogen Peroxide and Degradation of an Azo Dye in Water

Abstract

A trickle bed electrochemical reactor was used to generate hydrogen peroxide in dilute electrolyte and then degrade an azo dye, i.e. reactive brilliant red X-3B in water by electro-Fenton process. The trickle bed reactor was composed of carbon black-polytetrafluoroethylene coated graphite chips. During the preparation of coated graphite chips, coating times and surfactant dosage were optimized to improve electro-generation of H₂O₂. In addition, the optimal electrolysis conditions for H₂O₂ electro-generation were obtained as follows, cell voltage of 4.5 V, air flow rate of 0.1 m³/h, electrolyte flow rate of 15 mL/min, and initial pH of 3. Under the given conditions, H₂O₂ concentration, production rate and current efficiency were 5.01 mmol/L, 134 μmol/(h·cm²) and 63.7%, respectively, after 1 h of electrolysis. With addition of 0.1 mmol/L Fe²⁺, 123 mg/L X-3B was completely removed from water after 30 min of electro-Fenton treatment, whereas total organic carbon dropped slowly from 17.8 mg/L to 2.28 mg/L (87% mineralization) after 3 h. The trickle bed reactor was sufficient to treat low-strength wastewater or be used in tandem with other treatment units.