Photo-assisted self-driven bioelectrochemical systems for simultaneous enhanced treatment of etching terminal wastewater and selective recovery of heavy metals

Abstract

Practical application of photo-assisted bioelectrochemical systems (BESs) for actual etching terminal wastewater (ETW) treatment, requires its energy-saving and high treatment efficiency with simultaneous recovery of multiple heavy metals. Herein photo-assisted self-driven BESs composed of two serially connected microbial fuel cells (MFC) in-situ utilized for powering one microbial electrolysis cell (MEC), are continuously fed with actual ETW. Such BESs achieve enhanced recalcitrant organics mineralization (37.9–38.2%) with simultaneous Cu(II) recovery (68.2 ± 0.4%-69.1 ± 0.4%) in the cathodes of MFCs, along with those (recalcitrant organics mineralization: 29.9 ± 0.4%; Ni(II) recovery: 64.9 ± 0.0% on the cathode electrodes; Zn(II) recovery: 75.7 ± 1.4% at the cathodic bottoms) in the MECs without any external energy consumption, allowing the final effluent meeting the China national wastewater discharge standards. Active species of ·OH, O2·-, holes and H2O2 varying degrees contribute to recalcitrant organics mineralization in the MFC and MEC units. This study provides an alternative zero energy consumption approach for efficient mineralization of recalcitrant organics with simultaneous selective recovery and separation of multiple heavy metals in actual ETW, moving photo-assisted self-driven BESs closer to applicable complex wastewater treatment with simultaneous recovery of multiple value-added heavy metals.