Cathodic Optimization of a MFC for Energy Recovery from Industrial Wastewater

Abstract

In a photosynthetic MFC with algae at cathodic compartment, algae use inorganic carbon source, carbon dioxide, and sunlight and produce oxygen by photosynthesis. The oxygen produced is used at cathode as electron acceptor. In this way, the use of algae at the cathode of a MFC has interesting advantages: carbon dioxide fixation and oxygen supply. In order to study if algae form a biofilm on cathodic electrode of a photosynthetic microbial fuel cell and how this biofilm affects on performance of this photosynthetic MFC and on electricity production, cathodic electrode of a photosynthetic MFC at steady state was changed by another identical electrode. When cathode was changed, the cell voltage fell down from 14 mV to 0 mV (light phase). After 10 days, the cell voltage increased and steady state was reached after 22 days, with values of 9 mV (light phase). When electricity starts to increase after changing cathode, algae concentration in suspension decreased from 600 until 250 mg/L. The decrement of algae concentration and the increment of cell voltage indicated that algae in suspension could form a biofilm on cathodic electrode positively influencing on electricity production. The cathode polarization resistance increased after changing cathode due to the elimination of algae biofilm from electrode. Once biofilm was formed, this resistance decreased from 80800 until 23060 ?.