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

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 center dot O2-, 1O2, and center dot OH, were generated in the g-C3N4-NS/visible light system. center dot O2- and 1O2 were determined as the main active species, whereas photoelectric-hole and center dot 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 photogenerated 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 center dot OH. NO3- with the concentration of 10-100 mu mol/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.

Automated summary

Polycyclic aromatic hydrocarbons (PAHs) widely exist in aquatic environment and pose significant ecological risks to aquatic species. This study investigated the removal of a typical PAH, phenanthrene (PHE), using a non-metallic photocatalyst g-C3N4 under visible light irradiation. The results showed that g-C3N4-nano sheet achieved 100% removal efficiency of PHE within 10 minutes under visible light. Reactive oxygenated species, such as center dot O2-, 1O2, and center dot OH, were generated in the g-C3N4/visible light system, with center dot O2- and 1O2 identified as the primary active species. The study also examined the effects of co-existing substances, including humic acid (HA), Cl-, and NO3-, on the removal process.