On the design of a jet-aerated microfluidic flow-through reactor for wastewater treatment by electro-Fenton

Abstract

The design of cost-effective reactors for wastewater treatment by electrochemical advanced oxidation processes is still a challenge. In this work, a novel electro-Fenton reactor concept is presented. The combination of a jet aerator and a microfluidic flow-through cell configures a reactor with low ohmic drop, improved mass transfer which is, in addition, aerated by a compressor-free system. The production of H2O2 was assessed, obtaining an instantaneous production rate of 12.4 mg H2O2 cm−3 electrode h−1 at an instantaneous current efficiency of 98.6% with a low electrical energy consumption of 7.8 kWh kg H2O2−1 in 0.05 M Na2SO4 using a RVC with a deposition of CB/PTFE as the cathode. The performance of two mesh anodes (covered with mixed mineral oxides and boron doped diamond) and two cathodes (Duocel® RVC and Aluminium foams) was evaluated for the degradation of 0.75 dm3 with 100 mg dm−3 of clopyralid as model bio-refractory organic pollutant. The combination of BDD + CB/PTFE – Al was found to be synergistic due to the production of oxidizing radicals from water oxidation and electro-generated Fenton reagent. It was selected as the optimum configuration allowing a fast and efficient degradation of clopyralid after the application of approximately 0.44 Ah dm−3 (less than 1 h) resulting in an energy consumption of 0.02 kWh g−1 clopyralid at 20 mA cm−3 in a medium with only 7 mM Na2SO4 of supporting electrolyte.