Unprecedented efficient degradation of phenanthrene in water by intimately coupling novel ternary composite Mn3O4/MnO2-Ag3PO4 and functional bacteria under visible light irradiation

Polycyclic aromatic hydrocarbons (PAHs) are associated with adverse health effects in humans. The intimately coupled photocatalysis and biodegradation (ICPB) is considered as a prospective green technique to clean up pollutants from environment. In this work, the Mn3O4/MnO2 -cubic Ag3PO4 with exposed {1 0 0} facets (MnOx-cAP) exhibited enhanced photocatalytic activity for the degradation of typical PAHs (phenanthrene) under visible light illumination. The photocatalysts were characterized by XRD, FESEM, TEM, FTIR, Raman, UV-vis DRS, PL, BET and XPS. Noticeably, 0.4wt% MnOx-cAP composite exhibited the optimal photocatalytic activity with the degradation efficiency of phenanthrene (PHE) up to 96.2% within 20 min. Cyclic tests indicated the stability of MnOx-cAP composite over repeated use. A photocatalytic degradation mechanism associated with Ag surface plasmon resonance (SPR) effect over MnOx-cAP composite was proposed. Subsequently, this research estimated the elimination and mineralization of PHE using visible light-induced ICPB (known as VPCB) with 0.4 wt% MnOx-cAP as the photocatalyst. In the first 2 h of assay, VPCB accelerated PHE elimination by similar to 9% compared with photocatalysis alone. The biofilms in the VPCB sponge carriers evolved to being enriched in Shewanella, Sedimentibacter, Comamonas, Acinetobacter and Pseudomonas. The intermediates were analyzed by gas chromatography-mass spectrometer (GC-MS) technique and plausible VPCB pathways of PHE were proposed. PHE was transformed to non-toxic intermediates in 10 h. It seemed that the MnOx-cAP based VPCB would be promising for degrading persistent PAHs from a realistic point of view.