POWER GENERATION AND ETHANOLAMINES REMOVAL BY SINGLE AIR-CATHODE MICROBIAL FUEL CELLS

Abstract

Monoethanolamine (MEA), diethanolamine (DEA), and triethanolamine (TEA) are collectively called ethanolamines. Ethanolamines are composed of alcohol and amine groups, and are compounds having both characteristics. Ethanolamines Ethanolamines are used in a variety of industries from real-life personal care products, cosmetics to adsorbents for removing carbon dioxide from flue gases and natural gas, pH adjusters, and metal corrosion inhibitors. According to the International Agency for Research on Cancer (IARC), diethanolamine is used in cosmetics but can be combined with other substances to form carcinogens. On the other hand, due to this characteristic of ethanolamine with two functional groups, it causes the increase of chemical oxygen demand and total nitrogen concentration when flowing into the water system, which causes water pollution. Microbial fuel cells (MFCs) use exoelectrogenic bacteria to convert chemical energy into electricity without special devices, and exoelectrogenic bacteria can use a variety of substrates, from pure organic matter to various organic mixtures present in wastewater. Single air-cathode microbial fuel cells are simpler than conventional two-chamber systems and require no additional equipment because they use oxygen in the air instead of in the water. In this study, the voltage production, COD, and nitrogen removal rate of single air-cathode microbial fuel cells were compared and analyzed for each ethanolamines. Although the effects of substrate type and composition on the electrochemical performance of MFC have been extensively studied, this work has generally been performed using a substrate that does not contain nitrogen. Experiments were conducted without additional ammonium in the substrate. The nitrogen that present in the ethanolamines was used as the source of nitrogen. Unlike MEA and DEA, TEA was judged to be difficult to use internal nitrogen, so that NH4Cl was injected into the substrate as an additional nitrogen source. The results showed that the maximum voltage for MEA, DEA, TEA and TEA with NH4Cl’s reactors were 0.446, 0.452, 0.023 and 0.425 V, respectively. Also, COD removal was 85.7, 83.2, 31.2 and 87.6%. Nitrogen removal was 69, 76, 23.2 and 70.1%. Finally, Maximum power density was 453.2, 484.1, 4.0328 and 329.5 mW/m2. In summary, DEA is the most suitable substrate for MFCs among ethanolamines. In other experiments except TEA, the power density and nitrogen removal rate are inversely proportional. Nitrogen ions are considered to be an obstacle to the electron transport of a single air-cathode MFC.