Ecology & Safety ISSN 1314-7234, Volume 11, 2017 Journal of International Scientific Publications www.scientific-publications.net Page 55 SULFITE DRIVEN FUEL CELL FOR ENVIRONMENTAL PURPOSES: OPTIMIZATION OF THE OPERATING CONDITION M. Martinov, E. Razkazova-Velkova, S. Stefanov Institute of Chemical Engineering, Bulgarian Academy of Sciences, Acad. G. Bonchev, str. Bld.103, 1113 Sofia, Bulgaria Abstract Sulfite ions are by-products in different industrial processes. As they are highly toxic the way for their disposal is to oxidize them to harmless sulfates that can be commercially useful product such as building gypsum or fertilizers. The oxidation process used up to now is an expensive and energy consuming one. The present study is an attempt for their removal with energy generation at the same time in a fuel cell of our design. In our previous papers, we have shown the process of optimization of the design of the cell and the electrodes. This paper shows the process of optimization of the operating conditions by the choice of membranes, initial concentrations, electrolyte content and pH. Kew words: sulfite driven fuel cell, operating condition, optimization 1. INTRODUCTION In our age the demand for energy, electric or other, is ever increasing. According to the International Energy Agency, [IEA, http://www.iea.org/] for 2015 over 80% of all energy gained has come from fossil fuels. Fossil fuels contain varying quantities of sulfur that becomes a real environmental problem after the burning of the fuel when the sulfur is transformed to sulfur dioxide. Methods are developed to neutralize this hazardous product, but most of them are either too expensive for massive industrial applications or as in the cases of the lime and limestone methods require additional treatment that further complicates and increases the cost. Nevertheless all the ecological directives of the EU dictate that it is absolutely prohibited to release SO 2 in the atmosphere in high concentrations, which forces all factories and power plants to neutralize their flue gases despite the high costs. The most economical way of scrubbing SO 2 from flue gases is via hydrated lime (Ca(OH) 2 ) or limestone (CaCO 3 ) to CaSO 3 and via caustic soda (NaOH) to Na 2 SO 3 . Other industries whose wastewaters are contaminated with sodium sulfate are the pulp and paper industries (Kraft process), photographic industry (fixer), mineral processing (froth flotation), oil industry (oil recovery), food industry (preservatives) and textile industries (dyes). But sulfates in wastewaters are substances that need to be oxidized to sulfites before their disposal in the environment. The oxidation process is a high energy consuming one and is accompanied with a lot of exploitation difficulties. Many studies are dedicated to the kinetics of oxidation [Karatza D et al., ( 2004), Karatza D et al.,( 2008), Lancia A. et al.(1997), Lancia A. et al.(1999), Pisu M et al. , (2004)] as well as the improvement of apparatuses equipment [Gohara Wаdie F.and Steve Feeney, Zheng Y et al.(2003), Zheng Y et al.(2004),]. The high expenses make them inefficient for small-scale desulfurization installations. In recent years there is accelerating scientific interest for oxidation of different pollutants (including organic) in fuel cells (FC) [Kwiyong Kim and Jong-In Han, (2014), Razkazova-Velkova, E Razkazova-Velkova, E et al (2014), Zhai Lin-Feng, et al,]. This increasing interest is due to the possibility of eliminating pollutants with minimum exploitation costs while harvesting electrical energy at the same time. Particularly relevant way to be intensifying the process of oxidation of the pollutions is the use of micro-organisms in a so-called microbial fuel cells (MFC). But the possibilities for use of modern microbial fuel cells in our case are very limited because the sulfites are preservatives and are toxic for most bacterial species.