Hydrogen peroxide production in a pilot-scale microbial electrolysis cell

Abstract

A pilot-scale dual-chamber microbial electrolysis cell (MEC) equipped with a carbon gas-diffusion cathode was evaluated for H₂O₂ production using acetate medium as the electron donor. To assess the effect of cathodic pH on H₂O₂ yield, the MEC was tested with an anion exchange membrane (AEM) and a cation exchange membrane (CEM), respectively. The maximum current density reached 0.94-0.96 A/m² in the MEC at applied voltage of 0.35-1.9 V, regardless of membranes. The highest H₂O₂ conversion efficiency was only 7.2 ± 0.09% for the CEM-MEC. This low conversion would be due to further H₂O₂ reduction to H₂O on the cathode or H₂O₂ decomposition in bulk liquid. This low H₂O₂ conversion indicates that large-scale MECs are not ideal for production of concentrated H₂O₂ but could be useful for a sustainable in-situ oxidation process in wastewater treatment.

Keywords: Decomposition; Hydrogen peroxide; Microbial electrolysis cells; Peroxide loss; Pilot tests.

Fig. 1

Schematic diagram of a large-scale microbial electrochemical cell (MEC). (A) MEC components, (B) photo of the MEC, (C) anode modulation, and (D) photo of an anode module.

Fig. 2

The evolution of current density in the MEC. Red arrows indicate addition of tap water into the cathode due to catholyte evaporation.

Fig. 3

H₂O₂ concentration and H₂O₂ conversion efficiency in the MEC.

Fig. 4

Small-scale H₂O₂ electrolysis cell performance. Tests were performed in a dual chamber reactor with 10 mL cathode chamber volume using 0.1 M NaCl as electrolyte and the same GDE and AEM as used in the pilot MEC. Cathode potential was fixed at −1.25 V vs SCE. Hydraulic retention time was 0.6, 1.0, and 11.2 min, respectively. The same trends were observed for the cathode potential at −1.5 to −2 V vs SCE (data not shown).