OPTIMIZATION OF BIOCATHODES: BIOCHAR AS ELECTRODE MATERIAL FOR GROWTH OF ELECTROACTIVE BACTERIAS

ANTIC GORRAZZI SOFIA; MASSAZZA DIEGO; PEDETTA ANDREA; BUSALMEN JUAN PABLO; BONANNI P. SEBASTIAN

Congreso; SAMIGE 2022; 2022

Cathodic electro-active microorganisms can use an electrode as electron donor to reduce nitrates,sulfates or chlorinated compounds. In this context, the electrode acts as an inexhaustible electronsource that enhances microorganisms activity, allowing numerous applications related withbiocatalysis, biosynthesis and wastewater treatment. However, their application has been relegateddue to the low current density they produce. The performance of bioelectrochemical systemsdepends mainly on the ability and efficiency of microorganisms to adhere and exchange electronswith the polarized surface. The current density obtained on biocathodes may be limited by anadverse bacterial adherence on the electrode surface caused by electrostatic repulsion between the bacteria and the electrode. Still, basic studies are required to improve the interaction betweenelectroactive microorganisms and electrodes. Growth medium parameters such as ionic strength,presence of organic compounds, pH, flow rate, and temperature have been shown to affectadherence of bacteria to surfaces. On the other hand, material and surface properties such ashydrophobicity and electrostatic charge also play a fundamental role in the biofilm formationprocess. Biochar is a carbonaceous compound obtained through the pyrolysis of biomass.Previously, we found that this material has electrochemical properties that improvebacteria-electrode interaction. Biochar electrodes obtained at relatively low temperatures(600/800ºC) enhance current density produced by Geobacter sulfurreducens on anodes. Because the biochar has charged organic functional groups on its surface that could improve initial attachment of cathodic bacteria to electrodes, we test it as growing substrate in electrochemical cells. Biochar electrodes of different temperatures (500ºC-1200ºC) were polarized at -0,3V vs SHE. The growth of cathodic bacteria Thiobacillus denitrificans on biochar cathodes was followed by measuring the electric current density through chronoamperometry. Scanning microscopy images were taken to analyze bacterial coverage. In agreement with previous results with anodic bacterias, higher current densities were registered when biochar obtained at 600ºC/800ºC were used as electrode donor. Current densities values were comparable to those obtained with graphite, the most common electrode material used for the growth of electroactive bacteria. This results not only provided information to optimize biocathode performance, but also reinforces the evidence that biochar could be a cheap and ecofriendly electrode material, which revalues waste.