In this work, we reported a method for a fabrication of bead-on-string structured g-C3N4/CoFe2O4 composite nanofibers by electrospinning coupled with in situ calcination. For the first time, this catalyst effectively removed high concentrations of mixed organic pollutants through the synergistic effects of adsorption and photocatalysis. The composite materials removal efficiency of adsorption and photocatalytic for high concentrations of organic pollutants in wastewater can exceed 90%. Surface potential analysis using in situ Kelvin probe force microscopy demonstrated the electron transfer pathways on the catalyst surface. The formation of the heterojunction was demonstrated through DFT calculations to significantly enhance the efficiency of electron–hole separation. This work provided valuable insights for the development of efficient catalysts for the synergistic adsorption-photocatalytic treatment of environmental pollutants, thus addressing increasingly severe environmental challenges.

Environmental-friendly photocatalytic technology is attracting considerable attentions in the filed of antibiotic degradation. In this work, an innovative Ag/ZnO/Bi2WO6 catalyst was fabricated using sol–gel and ultrasonic methods for the degradation cefuroxime sodium in wastewater. The optimized Ag/ZnO/Bi2WO6 photocatalyst demonstrated the a remarkable 77.0% photocatalytic efficiency within 180 min under simulated solar sunlight, with an apparent rate constant of 0.01085 min− 1. This efficiency is notably 6.02 and 1.41 times higher than that of pure ZnO and Ag/ZnO, respectively. The Ag/ZnO/Bi2WO6 photocatalyst achieved a degradation efficiency of up to 72.3% in tap water and polluted river water, while achieving 65.7% degradation in pulping wastewater and pharmaceutical wastewater. Experiments involving reactive species scavenging and electron paramagnetic resonance implied that hydroxide radicals were the predominant active species responsible for the degradation. The enhanced catalytic mechanism and degradation pathway were elucidated, providing valuable insights into the construction and development of high-performance catalysts based on zinc oxide.

Fe3O4/g-C3N4/TiO2 catalyst has been fabricated using a simple ultrasonic method with high photocatalytic activity. The morphology, structure and optical properties of Fe3O4/ g-C3N4/TiO2 were systematically investigated by a variety of characterization techniques. The optimum degradation conditions were investigated by degrading tetracycline (TC) under visible light irradiation. The results showed that the degradation efficiency was the highest when the initial TC concentration was 5.0 mg/L, the pH value was 11 and the catalyst dosage was 1.0 g/L. After 100 min of visible light irradiation, the degradation efficiency of TC achieved at 73.61%, which was 1.64 and 1.19 times that of g-C3N4 and Fe3O4/ g-C3N4, respectively. Moreover, Fe3O4/ g-C3N4/TiO2 had good stability and recyclability. The results of capture experiments showed that ‧O2 − and ‧OH were the main active species during the photocatalytic process, and a possible photocatalytic reaction mechanism of Fe3O4/ g-C3N4/TiO2 catalyst was proposed. This study provides a new way to improve the photocatalytic performance of g-C3N4, which has great potential in degrading pollutants such as antibiotics in wastewater.

Graphene-derived materials are an excellent electrode for electrochemical detection of heavy metals. In this study, a MnO2/ graphene supported on Ni foam electrode was prepared via ultrasonic impregnation and electrochemical deposition. The resulting electrode was used to detect Pb(II) in the aquatic environment. The graphene and MnO2 deposited on the Ni foam not only improved active surface area, but also promoted the electron transfer. The electrochemical performance towards Pb(II) was evaluated by cyclic voltammetry (CV) and square wave anodic stripping voltammetry (SWASV). The prepared electrode exhibited lower limit of detection (LOD, 0.2 μM (S/N = 3)) and good sensitivity (59.9 μAμM−1) for Pb(II) detection. Moreover, the prepared electrodes showed good stability and reproducibility. This excellent performance can be attributed to the strong adhesion force between graphene and MnO2, which provides compact structures for the enhancement of the mechanical stability. Thus, these combined results provide some technical considerations and scientific insights for the detection of heavy metal ions using composite electrodes.

Highly luminescent carbon quantum dots (CQDs) are developed as fluorescent probes for selective detection of the heavy-ion Fe3+, where the CQDs exhibit excellent nontoxicity, functionalizability, sensitivity, and selectivity. Biomass-based CQDs and nitrogen-doped CQDs (N-CQDs) are synthesized for the selective detection of Fe3+ by using H2O2 as an oxidant and polyetherimide (PEI) as a nitrogen precursor by a green hydrothermal synthesis method. The prepared CQDs and N-CQDs exhibit an elliptical morphology and with an average particle size of 7 and 4 nm, respectively, and emit blue photoluminescence at 445 and 468 nm under excitation at 367 and 343 nm, respectively. The CQDs and N-CQDs exhibit good water solubility because of the abundant hydroxyl and carboxyl/carbonyl groups and graphic/pyrrolic/pyridinic nitrogen on the surfaces, giving rise to a quantum yield of about 24.2% and 30.7%, respectively. Notably, the Matrimony vine-PEI-based CQDs exhibit excellent Fe3+ selectivity and sensitivity relative to the Matrimony vine-based CQDs due to complexation of the numerous phenolic hydroxyl groups and nitrogen-containing groups with Fe3+, leading to increased fluorescence quenching, which greatly improves the sensitivity of detection. The minimum detection limit was 2.22 μmol L− 1 with a complexation constant of 44.7.