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Endogenous inorganic carbon buffers accumulation and self-buffering capacity enhancement of air-cathode microbial fuel cells through anolyte recycling
- Chen, Jinli, Lv, Ying, Wang, Yue, Ren, Yueping, Li, Xiufen, Wang, Xinhua
- The Science of the total environment 2019 v.676 pp. 11-17
- acetates, acidification, bacteria, bicarbonates, buffers, carbon dioxide, carbonates, electric power, inorganic carbon, metabolism, microbial fuel cells, models, recycling
- Anolyte acidification is inevitable in the operation of buffer-free microbial fuel cells (MFCs), which restricts the proliferation and metabolism of electroactive bacteria, and results in electric-power deterioration. The anodic metabolic end-products, inorganic carbons (IC), which are composed of H2CO3 (dissolved CO2), HCO3−, and CO32−, are ideal endogenous buffers, whereas the naturally accumulated IC are far from enough to prevent anolyte acidification. In this work, different volume ratios of the anolytes (10%, 30%, and 50%) were recycled to increase the IC concentrations of the single-chamber air-cathode buffer-free MFCs. Under anolyte recycling running mode, IC accumulation agreed with the SGompertz model and the fitting IC-asymptotic concentrations (ICAC) grew exponentially to 18.5 mM, 24.4 mM, and 32.8 mM as the anolyte recycling ratio increased from 10% to 30% and 50%. Self-buffering running can be realized when the anolyte recycling ratio exceeds 50% for the MFC feeding on 1 g·L−1 of acetate. The electric power for the 50% recycling scenario increased from the baseline control of 272.4 mW·m−2 to 628.5 mW·m−2. The coulombic efficiency (CE) was also apparently improved. This paper for the first time clarifies the accumulation law of endogenous IC buffers under anolyte partially recycling mode and their self-buffering effects.