Fabrication Of TiO₂ And G-C₃N₄ Composites And For Their Degradation Mechanism Of Naproxen

With economic development,the increasing use of pharmaceuticals and personal care products（PPCPs）has led to their high frequency detection in urban sewage and natural water bodies.Due to the biological toxicity,pseudo-persistence and bioaccumulation of PPCPs,even at low concentrations（ng/L～mg/L）,PPCPs will pose a threat to human health and the ecological environment.Therefore,the development of efficient removal technology of PPCPs in water has become a hot issue in the environmental field.In recent years,semiconductor-based photocatalytic technology has been considered as a highly efficient and environmentally friendly PPCPs treatment technology because it can directly use solar energy to produce a series of active species to degrade pollutants.Metal oxide TiO₂ and non-metal g-C₃N₄semiconductor materials have been widely used in the degradation of PPCPs due to their suitable photoredox capacity and favourable photocatalytic performance.However,the traditional TiO₂ has the disadvantages of low quantum yield and narrow light response range,and the bulk g-C₃N₄ has a small specific surface area,poor visible light absorption ability and high photo-generated charge carriers recombination rate,which greatly limits their application in the field of photocatalysis.In this paper,TiO₂ and g-C₃N₄-based photocatalysts are employed as substrates,and the active sites and specific surface area are adjusted by controlling the crystal surface exposure and morphology of the material.The metal material（silver carbonate Ag₂CO₃）or non-metallic material（carbon dots CDs）with a good light absorption range was used to modify the photocatalysts,while improving the separation efficiency of charge carriers.The designed high-activity composites are applied to the photocatalytic degradation of typical PPCPs.Through characterization and experiments,the photocatalytic mechanism of the photocatalysts,the degradation mechanism of pollutants and product toxicity,and the effect of natural water matrix on the degradation process are systematically studied.The main research contents are as follows:A novel Z-scheme Ag₂CO₃/TNS-001 nanocomposite photocatalyst with excellent solar-light response was synthesized using a simple hydrothermal and deposition reaction.The Ag₂CO₃/TNS-001 exhibited superior photocatalytic activity for removal of naproxen（NPX）under solar light irradiation,demonstrating kinetics of 40.7,23.9,and 6.9 times higher than that of Ag₂CO₃,P25,and TNS-001,respectively.This remarkably improved photocatalytic efficiency was attributed to the synergistic effects of highly active（001）facets,efficient solar light response,and enhanced separation of photogenerated carriers.The charge transfer process was confirmed to be Z-scheme mechanism via scavenging experiments and electron paramagnetic resonance（EPR）analysis.Intermediate detection and density functional theory（DFT）calculations revealed the degradation mechanism of NPX.Moreover,the chlorella acute toxicity test indicated that mineralization translated to a reduction in the toxicity of the NPX solution.In order to enrich the diversity of PPCPS nanomaterials for photocatalytic degradation,we studied the typical non-metal g-C₃N₄ materials.In this work,a novel metal-free photocatalytic nanoreactor was successfully fabricated by anchoring carbon dots to hollow carbon nitride nanospheres（HCNS/CDs）.The unique hollow nanospherical structures of the HCNS/CDs endowed them with a high population of reactive sites,while enhancing optical absorption due to internal light reflection.Simultaneously,the CDs served as“artificial antennas”to absorb and convert photons with low energy due to their superior up-converting properties.As a result,the HCNS/CDs demonstrated excellent photodegradation activity for the degradation of PPCPs under broad-spectrum irradiation.Remarkedly,10 mg/L of naproxen（NPX）was completely decomposed following 5 min of natural sunlight irradiation.Further mechanism revealed that the O₂^·-plays a significant role during the photocatalytic process,which could lead to the final mineralization of NPX.Effects of natural water matrices further revealed that this photocatalytic system may be efficaciously applied for the remediation of PPCPs contamination in ambient waterways.