Insight into the highly efficient degradation of PAHs in water over graphene oxide/Ag3PO4 composites under visible light irradiation

Polycyclic aromatic hydrocarbons (PAHs) are associated with adverse health effects in humans, and the photocatalysis degradation is regarded as promising technology to remove contaminants from environment. Although many TiO2-based photocatalysts were reported to be active for this process, the efficiency is still quite low. In this work, graphene oxide (GO) enwrapped silver phosphate composites were found to exhibit superior activities in the photocatalytic degradation process of a variety of PAHs (naphthalene, phenanthrene and pyrene) under visible light irradiation. The optimum amount of GO was 3.0 wt%. Within several minutes or even seconds' visible light irradiation, naphthalene, phenanthrene and pyrene can be completely oxidized. Meanwhile, good photocatalytic activity was retained after six cycles run. The trapping experiments gave evidence that degradation was mediated by photogenerated holes, superoxide radicals and hydroxyl radical, different from others % OH was found to play a role in the process of pyrene photoreaction. Gas chromatography-mass spectrometer (GC-MS) technique was employed to analyze photodegradation intermediates. Based on the identified intermediates, the plausible photooxidation pathways of PAHs over the surface of GO/Ag3PO4 were proposed. Ultimately, a possible synergetic mechanism associated with Ag surface plasmon resonance effect of GO/Ag3PO4 composite for PAHs photodegradation was suggested. The superior photocatalytic system for the removal of PAHs was presented and simultaneously it shed light on photodegradation of PAHs from a practical point of view.