In this study, the intermediates of the photocatalytic degradation of tetracycline hydrochloride (TC‐HCl) were analyzed by high performance liquid chromatography‐mass spectrometry. The doping of polypyrrole (PPy) and carbon nanotubes (CNTs) increased the reaction rate of TC‐HCl degradation by ZnO. The prepared ZnO has a large specific surface area, which can improve the adsorption performance. The introduction of PPy and CNTs can promote electron transfer and reduce the recombination of photogenerated electron hole pairs in the composite material ZnO/PPy/CNTs(ZPC), and the photocatalytic performance of the composite sample is improved. In addition, the new visible light catalyst has strong degradation effect on TC‐HCl. Using tetracycline hydrochloride as a pollutant, the photocatalytic degradation performance of each sample was analyzed. After 240 min of photoreaction, the Degradation rate of TC‐HCl (DTC‐HCl) by ZnO was 24.1 %, while that by ZPC was 91.5 %. Meanwhile, the intermediates of photocatalytic degradation of TC‐HCl were analyzed by high performance liquid chromatography‐mass spectrometry. The peak intensity of TC‐HCl from adsorption equilibrium to the end of the photocatalytic reaction occurred at a retention time of about 10.05 min and decreased with the increase of the reaction time. This indicates that TC‐HCl is broken down into small molecules during the reaction. Through the analysis of intermediates and active species, the degradation pathway of tetracycline hydrochloride was deduced.

Graphite-carbon nitride (g-C3N4) was prepared by thermocondensation, and g-C3N4/BiVO4 material (GCB) and g-C3N4/CNTs composite material (GCC) were prepared by doping different contents of BiVO4 and carbon nanotubes (CNTs) with g-C3N4 samples, respectively. Then, BiVO4, CNTs, and g-C3N4 samples with different contents were doped to prepare ternary composite material (GCBC). In the performance experiment, Sulfamethoxazole (SMZ) was used as degradation material to evaluate the photocatalytic performance of the prepared samples, and the degradation reaction kinetics equation, quadric cycle stability experiment, free radical capture, and intermediates identification were studied. The intermediates of photocatalytic degradation of SMZ were analyzed by high-performance liquid chromatography-mass spectrometry. From the experimental data, it can be seen that for SMZ solution, when the reaction time T = 0 min and retention time rt = 7.53 min, there is a peak corresponding to the substance with m/z [M + H]+ of 254, which is judged as SMZ. At 20, 40, and 60 min, rt was 2.00, 7.06, and 9.57 min, indicating the presence of intermediates in the photocatalytic process. Experimental analysis shows that there are three intermediates of SMZ degradation by composite sample GCBC. In this work, three kinds of composite materials were successfully prepared, and a variety of characterization, SMZ as pollutants, test the photocatalytic performance of composite materials (GCB, GCC, and GCBC) samples, and elucidated the cyclic stability of the material, active species capture, and photocatalytic degradation mechanism.

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Using an ultrasound-assisted chemical technique, ZnO quantum dot and ZnO composites were created. The optical characteristics and structural details of these composites were examined using TEM, XRD, XPS, FT-IR, UV-vis, and BET. The results revealed that both the ZnO quantum dot composite and ZnO composite exhibited outstanding optical properties, making them suitable for photocatalytic reactions. In order to analyze the photocatalytic performance, a degradation experiment was conducted using Rhodamine B solution as the simulation dye wastewater. The experiment demonstrated that the degradation of Rhodamine B followed the first-order reaction kinetics equation when combined with the photocatalytic reaction kinetics. Moreover, through cyclic stability testing, it was determined that the ZnO QDs-GO-g-C3N4 composite sample showed good stability and could be reused. The degradation rates of Rhodamine B solution using ZnO-GO-g-C3N4 and ZnO QDs-GO-g-C3N4 reached 95.25% and 97.16%, respectively. Furthermore, free-radical-trapping experiments confirmed that ·O2− was the main active species in the catalytic system and its photocatalytic mechanism was elucidated. The photocatalytic oxidation of ZnO quantum dots in this study has important reference value and provides a new idea for the subsequent research.