Streamlining of commercial berl saddles: new material to improve the performance of Microbial Fuel Cells

Microbial fuel cell (MFC) is a prospective technology that allows oxidizing organic and inorganic matter to generate current by activity of bacteria. Recently, interest in the electrode material has steadily increased the performance of MFCs. Electrode-based materials should have good electrical conduction, chemical stability and biocompatibility, and should guarantee efficient electrons transfer between the bacteria and electrode surface. Additionally, to render MFCs a cost-effective and energy sustainable technology, low-cost packing materials can be employed as support for bacteria growth and proliferation. In the present work, we used ceramic berl saddles, which is extensively used in Unit Operation of Chemical Engineering as well as in biotechnology processes to favor biomass adhesion. Considering that microbial fuel cells combine biological process with traditional fuel cell one, it is necessary to render conductive the packing material. Therefore, in this work, deposition of a conductive carbon layer on ceramic berl saddles was performed to obtain a novel low cost anode material necessary for the direct recovery of electrons by bacteria metabolisms. α-D-glucose was used as carbon layer source on the berl saddles. The impregnation processes with glucose solution (500g/L) underwent the following consecutive sequence: (i) drying, (ii) caramelization, and (iii) pyrolysis. The phase composition of the samples was determined by Raman Spectrometer (Renishaw) with laser excitation wavelength 514 nm. The Raman spectra obtained were typical of polycrystalline graphitic carbon, with a certain disorder arising from nanostructuring of clusters indicated by the presence of D peak. The position of G peak was shifted respect to that of pure graphite (1581 cm-1) to 1593 cm-1, indicating some degree of nanostructuring of graphitic clusters. The surface area and pore size distribution were determined by a Tristar II 3020 gas adsorption (BET). After deposition of carbon on the berl saddles was obtained an increase in surface area and porosimetry, both keys points for the overall anode performance. The carbon-coated berl saddles were used as anode material in a two-compartments laboratory prototype of MFC, in batch mode, using Saccaromyces cerevisiae as active microorganism. Electrochemical experiments were carried out in terms of open circuit voltage and Linear Sweep Voltammeter behavior of the MFC, using a Bio-Logic potentiostat. Results show a maximum power density of 12 mW/L using carbon-coated berl saddles, which is comparable to results obtained previously with commercial carbon felt, tested under the same condition as anode in MFCs. The results confirmed that the innovative carbon-coated berl saddles could be used as anode packing in MFC, favoring electrical requirements and bacteria adhesion.