Removal of polycyclic aromatic hydrocarbons by g-C3N4 nanosheets under visible light irradiation and effect of typical co-existence substances in river water

Abstract

Polycyclic aromatic hydrocarbons (PAHs) ubiquitously exist in aqueous environment, posing considerable chronic and acute ecological risk to aquatic species. Non-metallic photocatalyst g-C3N4 is a promising photocatalyst that can be used in river remediation under visible light irradiation. The removal of a typical PAH phenanthrene (PHE) by g-C3N4 under visible light was detailed studied. The removal efficiency of PHE (initial concentration 5 mg/L) by g-C3N4-nano sheet (NS) (1 g/L) reached 100% within 10 min under visible light. Reactive oxygenated species, including •O2-, 1O2, and •OH, were generated in the g-C3N4-NS/visible light system. •O2- and 1O2 were determined as the main active species, whereas photoelectric-hole and •OH were also involved in the reaction. The effects of co-existed substances were investigated, including humic acid (HA), Cl-, and NO3-. HA decreased the removal rate of PHE, probably due to its reaction with photo-generated holes. Cl- with lower concentration (0.2 – 10.0 mmol/L) decreased the removal rate of PHE, while with higher concentration (20 mmol/L) increased the removal rate of PHE, probably because of the interaction of Cl- with •OH. NO3- with the concentration of 10–100 μmol/L did not significantly affect the removal rate of PHE. This study will provide a possible in-situ route for the removal of typical PAHs in urban river environment.