Synergistic light irradiation and circuital current for efficient mineralization of recalcitrant organics and sequential recovery of heavy metals from etching terminal wastewater using photo-assisted bioelectrochemical systems

Abstract

Practical application of photo-assisted bioelectrochemical systems (BESs) requires its treatment for actual wastewaters. Herein photo-assisted BESs fed with actual etching terminal wastewater (ETW), achieve sequentially recovering copper (85.8 ± 2.3%) in one microbial fuel cell (MFCCu), nickel (71.6 ± 0.2%) in one microbial electrolysis cell (MECNi) and zinc (67.7 ± 1.3%) in the other MEC (MECZn) with simultaneous efficient mineralization of recalcitrant organics in each units (MFCCu: 34.1 ± 0.8%; MECNi: 22.8 ± 1.3%; MECZn: 13.7 ± 2.7%) and the effluent meeting China wastewater discharge standard. Light irradiation and circuital current play synergistic roles in recalcitrant organics mineralization and heavy metals recovery, 1.9–4.2 folds (organics mineralization) and 1.2–1.4 times (heavy metals recovery) of sole circuital current, and 3.5–7.1 times (organics mineralization) and 35.8–112.8 folds (heavy metals recovery) of light irradiation only. Oxidative active species (˙OH, O2·-, holes and H2O2) variably contribute to recalcitrant organics mineralization whereas heavy metals recovery is mainly ascribed to circuital current. This study provides an alternative and environmentally benign approach for recovery and separation of multiple heavy metals with simultaneous efficient mineralization of recalcitrant organics in ETW, moving photo-assisted BESs closer to applicable ETW treatment.