Preparation and characterization of ternary composite photocatalyst for degradation of oxytetracycline hydrochloride in seawater under visible light.

Oxytetracycline hydrochloride is the most widely used veterinary antibiotic in aquaculture. The presence of large amounts of residual antibiotics in aquaculture wastewater harms the ecological environment. In this study, the ternary composite of Zn0.75Mn0.75Fe1.5O4/ZnFe2O4/ZnO (ZMF-ZF-Z) photocatalyst was prepared by the coprecipitation method for degradation of oxytetracycline hydrochloride in marine aquaculture wastewater. The crystal phase, structure, morphology, elemental composition, element content, and optical properties of photogenerated electron-hole pairs of catalyst were characterized by XRD, SEM, EDS, UV-VIS (DRS), PL spectroscopy, and other test methods. The results showed that ZMF-ZF-Z photocatalyst had a larger response range of visible light than pure ZnO, which can absorb more natural light. During the process of the experiment, the photocatalytic effect of Z ZMF-ZF-Z photocatalyst was almost no weakening after 5 times reuse, which means quite good stability of the photocatalyst. Under the visible light irradiation, the degradation rate of oxytetracycline hydrochloride in seawater was 77.11% with ZMF-ZF-Z photocatalyst, which was about 3 times higher than that of pure ZnO, and the photocatalytic activity was significantly improved. This research provides a scientific and effective method for degrading antibiotics in seawater in actual production and life.

Adsorption of chlortetracycline in aquaculture wastewater by lanthanum modified multi-walled carbon nanotubes.

The lanthanum modified multi-walled carbon nanotubes (La-CNTs) prepared by an impregnation method were investigated for the adsorption of chlortetracycline (CTC) in aquaculture wastewater. The adsorbents were characterized by SEM, EDS, XRD and BET. The effects of some factors including La-containing impregnant concentration, adsorbent dosage, CTC adsorbate concentration, adsorption time, pH of the adsorbate solution and additional ions on the CTC adsorption by La-CNTs were investigated in detail, and the optimal adsorption conditions were determined. The adsorption kinetics obeyed the quasi-second-order kinetic model. The adsorption isotherms obeyed the Langmuir model and the fitted maximum capacity of La-CNTs for CTC adsorption was 55.3 mg/g.