Continuous Hydrogen Peroxide Production in Microbial Electrochemical Cells

Sunday, February 14, 2016
Nadratun Chowdhury, School of Engineering Matter, Transport & Energy, Arizona State University, Tempe, AZ
Hydrogen peroxide (H2O2) is a commonly used chemical in the water and wastewater industries. H2Ois an oxidizing agent to organic contaminants in water. H2Ois coupled with the Fenton process or UV treatment in advanced oxidation processes to disinfect drinking water. Complex organic contaminants can be oxidized by H2O2 to form simpler products that are bioavailable for consumption by microorganisms. Currently, 95% of H2Ois produced using the anthraquinone process, which requires large amounts of energy and uses potentially carcinogenic catalysts. Producing H2Ousing microbial electrochemical cells (MECs) may be a more sustainable alternative to these processes. An MEC consists of an anode, where bacteria oxidize wastewater organics and respire electrons to the anode to produce current. The reduction of O2 is carried out with relatively low-cost catalysts at the cathode. My MEC is a flat plate reactor with two chambers. It includes a carbon fiber, which serves as the anode, an anion exchange membrane and a carbon cloth exposed to catholyte on one side and air on the other. All of these components have areas of 49 cm2, and are compressed together to construct the MEC. The MEC is fed continuously at the anode chamber with acetate media. The MEC operates at a set air flow with a chosen electrolyte and a set hourly retention time (HRT). My research objective is to demonstrate continuous H2O2 production and optimize operation conditions for H2O2 production. This MEC is the first continuously produce H2O2, and at concentrations greater than 0.15%The cathode chamber was fed continuously for more than two months without downtime.  My MEC produced a maximum H2O2 concentration of 0.3076 wt%, using 200 mM NaCl electrolyte with no EDTA stabilizer, 20 ccm air flow rate and 4 hour HRT. Increasing HRT from 1 and 4 hours led to an increase in H2Oproduction from about 0.12 wt% to 0.3 wt%; 6 hour HRT showed a decrease in H2O2. Changes in air flow rate have no significant effect on H2Oproduction. Including EDTA as a H2O2 stabilizer decreased H2Oproduction from about 0.35 wt% to 0.15 wt%, likely due to its diffusion through the AEM to the anode chamber preventing microbial growth. In future research, I will test other electrolytes for improved H2O2 production. I believe that sustainable technologies like MECs have the potential to remediate wastewater and produce H2O2 for water disinfection at remote communities that do not have access to clean, running water, like the rural communities on the Navajo and Hopi reservations and military forward operating bases.