Polypyrrole/sewage sludge carbon as low-cost and high-effective catalyst for enhancing hexavalent chromium reduction and bio-power generation in dual chamber microbial fuel cells

Abstract

Microbial fuel cell, a potential bio-electrochemical energy transducer can extract the bio-energy from wastewater by the consumption of the electro-active microorganism adhered the surface of anode, and the MFC performance is greatly inhibited by the cathode catalysts. Herein, polypyrrole/sewage sludge carbon electrode is fabricated by an electro-polymerization loading method and the electrode is employed as the cathode electrode in MFC for the removal of Cr(VI) and bio-energy release at the same time. The electrochemical analysis finds the polypyrrole/sewage sludge carbon electrode exhibits the low charge transfer resistance and Tafel slope, which can demonstrate that the polypyrrole/sewage sludge carbon electrode possesses strong conductivity and excellent electrochemical activity. In addition, Cr(VI) in the cathode chamber of MFC with the polypyrrole/sewage sludge carbon electrode can be totally removed at 30 h. And the maximum output power and Cr(VI) reduction rate of MFCs are 760.7 mW m−2 and 2.16 g·m−3·h−3, which are 2.79 and 1.51 times higher than those of carbon cloth electrode (272.5 mW·m−2 and 1.43 g·m−3·h−3). Moreover, Cr(VI) can be removed and deposited on the electrode in the form of Cr(OH)3. And polypyrrole plays an electron shuttling role in reducing the internal resistance of MFC and enhancing electrochemical activity of the electrode for Cr(VI) reduction. Consequently, the polypyrrole/sewage sludge composite can achieve more stable Cr(VI) removal and power than those of sewage sludge carbon, polypyrrole, and carbon cloth electrodes, demonstrating an effective and low-cost catalyst for accelerating Cr(VI) reduction and strengthening bio-power production.