Novel VUV/g-C3N4 system with high adaptability to varied environmental conditions and outstanding degradation capacity for chlorophenols

Enhanced antibiotic degradation via photo-assisted peroxymonosulfate over graphitic carbon nitride nanosheets/CuBi2O4: Highly efficiency of oxygen activation and interfacial charge transfer

Improving the activation capacity of peroxymonosulfate (PMS) to increase radical and non-radical production is critical for antibiotic degradation. However, how to boost reactive oxygen species (ROS) and speed interfacial charge transfer remains an essential challenge. We report a coupling system of 10 %CNNS/CuBi2O4 photocatalyst and sulfate radical-based advanced oxidation processes (SO4--AOPs) to enhance the activation of PMS and improve antibiotic degradation. Owing to highly efficient oxygen activation and interfacial charge transfer, the degradation efficiency of the photo-assisted PMS system was as high as 51.6 times and 2.8 times that of photocatalyst and SO4--AOPs alone, respectively. Importantly, the highly efficient oxygen activation resulted in the production of O2-, which in turn could utilize the excess electrons generated through efficient interfacial charge transfer to convert into non-radical 1O2. The total organic carbon (TOC) elimination effectiveness of the photo-assisted PMS system reached 82 % via the synergy of radicals and non-radicals (O2-, OH, 1O2, SO4-, h+). This system also had excellent potential for reducing the generation and toxicity of disinfection by-products (DBPs), as evidenced through significant reductions in concentrations of trichloromethane (TCM), dichloroacetic acid (DCAA), and trichloronitromethane (TCNM) by 76 %, 64 %, and 35 %, respectively, providing an effective and eco-friendly strategy for antibiotic treatment.

Exploring the mechanism of norfloxacin removal and active species evolution by coupling persulfate activation with biochar hybridized Fe3O4 composites

In situ growth of dispersed active sites on substrates is a strategy for designing highly efficient catalysts for sulfate radical (SO4•-)-based advanced oxidation processes (SR-AOPs). Here, magnetic biochar composite (Fe3O4/BC) was fabricated as an activator to trigger PDS (peroxydisulfate) for norfloxacin (NOR) removal, achieving reliable NOR removal efficiency (>90%) within 10 min. Based on the synergistic effect between Fe3O4 and BC, the removal rate increases to 0.0265 L mg-1 min-1. Fe3O4/BC exhibited decent adaptability, stability, and recyclability toward affecting factors variation during PDS activation, attributed to the synergistic effect between Fe3O4 and BC. The electron transfer of magnetic Fe3O4 coupled with the adsorption and conduction function of carbon skeleton, which overcomes typical problems as crystal agglomeration, metal leaching, and catalysts recovery etc. The electron-rich Fe(II) sites promote the radical pathway by generating reactive oxygen species (ROS, •OH, SO4•- and O2•-), and radicals evolution contributing to the form of 1O2 in non-radical pathway. Under the effect of multipath in NOR degradation, HPLC-QTOF-MS spectroscopy and DFT calculation revealed the possible degradation pathway of NOR. In addition, according to toxicity prediction, the overall NOR contamination toxicity of NOR was effectively alleviated by Fe3O4/BC + PDS system. Overall, this study presents a promising composite in PDS activation and views the active species evolution in the NOR removal system, which is crucial for mechanism study in relevant research in the future.

Enhanced Photocatalytic Degradation of P-Chlorophenol by ZnIn2S4 Nanoflowers Modified with Carbon Quantum Dots

The removal of chlorophenol (CP) contaminants from water is a great challenge owing to their natural robustness and the toxic chlorinated by-products generated in degradation processes. In this work, a series of three-dimensional nanoflower-like structured photocatalysts (CQDs/ZnIn2S4-x, x = 1, 2, or 3 wt%) were fabricated via a facile hydrothermal approach. Excellent photocatalytic abilities toward 4-CP degradation under Xe lamp irradiation were achieved over the as-prepared composites. The removal efficiency of total organic carbon for 4-CP on the optimized CQDs/ZnIn2S4-2 was 49.1%, which was 16.0% higher than that of ZnIn2S4. The presence of CQDs could not only be used to adjust controllable band structures for enhancing light absorption, but it could also serve as an electron acceptor to promote the transition of electron–hole pairs. Moreover, a possible degradation mechanism of 4-CP was also proposed according to the analyses of active species, electron paramagnetic resonance characterization, degradation products, and attacked sites. Overall, this work unveils a superior function of an efficient photocatalyst for refractory organic pollutants.

Photocatalytic Applications of g-C3N4 Based on Bibliometric Analysis

To further understand the application of g-C3N4 in the field of photocatalysis, this study focuses on the visualization and analysis of articles in this field using VOSviewer and Citespace. These articles were analyzed in terms of number of articles, journals, authors, countries and keywords, respectively. The results show that there is little collaboration among the core authors in this field and insufficient cross-directional communication; the current applications of g-C3N4 are concentrated on hydrogen evolution, CO2 reduction and water treatment. The developing trend is in the direction of constructing Z-scheme structures, regulating the separation of photogenerated carriers and reducing the recombination rate, to which more and more attention is being paid. In the future, cross-directional communication among scholars can be strengthened to promote faster development of the field of photocatalytic applications of g-C3N4.

Pyrolyzing pharmaceutical sludge to biochar as an efficient adsorbent for deep removal of fluoroquinolone antibiotics from pharmaceutical wastewater: Performance and mechanism

This study explored the impact of pyrolysis parameters and modification methods on the characteristics of pharmaceutical sludge biochar, and investigated its capacity and mechanisms for levofloxacin (LEV), a typical fluoroquinolone antibiotics, adsorption. The results showed that S_BET of the biochar was improved with temperature increase, but decreased when temperature reached 900 °C. Under the optimal pyrolysis condition of 800 °C and 90 min, the biochar possessed the highest S_BET of 264.05 m² g^-1, excellent iodine value of 401.41 ± 3.84 mg∙g^-1 and phenol adsorption of 57.36 ± 3.39 mg∙g^-1. Among KOH, ZnCl₂, and CO₂ modifications, ZnCl₂ modification achieved the highest phenol adsorption of 123.40 ± 4.65 mg g^-1, with a significantly improved S_BET of 534.91 m² g^-1. The maximum LEV adsorption capacity of ZnCl₂ modified biochar, PZBC800, reached 159.26 mg g^-1, which overwhelmed the reported sludge biochars. BET, zeta potential, FT-IR, XPS, and Raman analysis, along with quantum chemistry calculation, revealed that pore filling, hydrogen bonding, π-π interaction, surface complexation, and electrostatic interaction were the main mechanisms for the excellent LEV adsorption performance of PZBC800. Deep removal (99.9%) of Fluoroquinolones (FQs) from pharmaceutical wastewater was also achieved by PZBC800 adsorption. The study promoted the development of pharmaceutical sludge biochar preparation and its application in advanced treatment of FQs pharmaceutical wastewater.