Autochthonous N-doped carbon nanotube/activated carbon composites derived from industrial paper sludge for chromate (VI) reduction in microbial fuel cells

The performance of microbial electrochemical system for hexavalent chromium (Cr (VI)) contaminant has been a severe challenge remaining active for further development. In this study, we developed a novel biochar material from industrial paper sludge for microbial fuel cell cathode fabrication to reduce aquatic Cr(VI) to non-toxic Cr (III). With additive melamine as nitrogen source and self-containing small portion of Fe as catalyst, the sludge evolved into electroactive biochar (BC-M) rendering a unique N-doped carbon nanotubes/activated carbon (N-CNT/AC) frame after pyrolyzecl at 900 degrees C for 2 h. Electrochemical analysis revealed enhanced electron transference capacity of this composite material, such effectiveness was attributed to the increased surface area and superior electroconcluctivity of N-doped CNTs. For performance of Cr(VI) reduction, a 55.1% reduction efficiency was achieved in an microbial fuel cell equipped with BC-M cathode while it reduced to about 41.8% when the cathode was replaced by electrode modified with no-melamine-involved biochar. The strategy of biochar upgrading from industrial paper sludge proposed in this work is expected to not only bring technical solution for low-cost CNT materials preparation for Cr(VI) reduction, but also put forward further research on value-added chemical synthesis from waste in various fields of energy and environment. (C) 2020 Elsevier B.V. All rights reserved.