Microbial reverse-electrodialysis chemical-production cell for acid and alkali production

A new type of bioelectrochemical system, called a microbial reverse-electrodialysis chemical-production cell (MRCC), was developed to produce acid and alkali using energy derived from organic matter (acetate) and salinity gradients (NaCl solutions representative of seawater and river water). A bipolar membrane (BPM) was placed next to the anode to prevent Cl- contamination and acidification of the anolyte, and to produce protons for HCl recovery. A 5-cell paired reverse-electrodialysis (RED) stack provided the electrical energy required to overcome the BPM over-potential (03-0.6 V), making the overall process spontaneous. The MRCC reactor produced electricity (908 mW/m(2)) as well as concentrated acidic and alkaline solutions, and therefore did not require an external power supply. After a fed-batch cycle, the pHs of the chemical product solutions were 1.65 +/- 0.04 and 11.98 +/- 0.10, due to the production. of 1.35 +/- 0.13 mmol of acid, and 0.59 +/- 0.14 mmol of alkali. The acid- and alkali-production efficiencies based on generated current were 58 +/- 3% and 25 +/- 3%. These results demonstrated proof-of-concept acid and alkali production using only renewable energy sources. (c) 2013 Elsevier B.V. All rights reserved.