Qianxin Zhang

Decoration of TiO2/g-C3N4 Z-scheme by carbon dots as a novel photocatalyst with improved visible-light photocatalytic performance for the degradation of enrofloxacin

A novel visible-light-driven carbon dot (CDs)/TiO2/g-C3N4 photocatalyst was successfully synthesized by doping CDs in TiO2 nanoparticles and the surface of g-C3N4 nanosheets via a facile hydrothermal process and was confirmed by characterization methods. UV-vis diffuse reflectance spectra (DRS) revealed that CDs/TiO2/g-C3N4 showed obvious additional absorption in the 370–450 nm region. DMPO spin-trapping ESR spectra demonstrated the existence of O2˙− and ·OH. The photocatalytic activity of the CDs (1.0 wt%)/TiO2/g-C3N4 was remarkably enhanced as compared to that of the single components (TiO2 and g-C3N4) and double component (TiO2/g-C3N4) towards the degradation of enrofloxacin (ENX) under visible-light irradiation. About 91.6% of ENX was decomposed by CDs (1.0 wt%)/TiO2/g-C3N4 in 1 h, which is nearly 3.95 times, 4.82 times, and 1.69 times that for TiO2, g-C3N4, and TiO2 (90.0 wt%)/g-C3N4, respectively. Scavenging experiments revealed that O2˙− and ·OH played key roles during the photocatalytic degradation of ENX. This study provides a simple and convenient method to modify materials with enhanced photocatalytic performance, and the CDs/TiO2/g-C3N4 catalyst is efficient, stable, and reusable for environmental practical applications.

Insights into the synergetic mechanism of a combined vis-RGO/TiO2/peroxodisulfate system for the degradation of PPCPs: Kinetics, environmental factors and products

In recent years, how to effectively remove emerging organic pollutants in water bodies has been studied extensively, especially in the actual complex water environment. In the present study, an effective wastewater treatment system that combined photocatalysis and an oxidizing agent was investigated. Specifically, visible-light driven reduced graphene oxide (RGO)/TiO2 composites were prepared, and peroxodisulfate (PDS) was used as electron acceptor to accelerate the photocatalytic activity of this material. The vis-RGO/TiO2/PDS system exhibited outstanding properties in the degradation of diclofenac (DCF), which was also facilitated by acidic conditions and Cl-. Lake water, tap water, river water and HCO3- decreased the DCF degradation rate, while NO3- affected the system only slightly. Low concentrations of fulvic acid (FA) promoted the degradation of DCF via the generation of excited states, whereas a high concentration of FA inhibited the degradation, which was likely due to the light screening effect. The photocatalytic mechanism revealed that PDS served as an electron acceptor for the promotion of electron-hole pair separation and the generation of additional reactive oxygen species, while the RGO served as an electric conductor. The active substances, h+, OH, 1O2, SO4- and O2- were generated in this system, O2- and h+ played significant roles in the degradation of DCF based electron spin resonance tests and radical quenching results. According to the mass spectrometry results, the amide bond cleavage, dechlorination reaction, hydroxyl addition reaction, and decarboxylation reaction were the primary transformative pathways.