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.

Photocatalytic degradation of marine diesel oil spills using composite CuO/ZrO2 under visible light.

Diesel oil spills in marine environments pose a severe threat to both aquatic and terrestrial ecosystems. Photocatalysis is an environment-friendly method for marine oil remediation; however, its practical usage is limited due to several issues. In this study, we demonstrate the enhanced efficacy of doped CuO/ZrO2 photocatalyst at degrading marine diesel in comparison to undoped ZrO2. The photocatalysts were prepared using co-precipitation method, and their physical and chemical properties were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and ultraviolet-visible spectroscopy (UV-Vis). XRD analysis showed that the photocatalytic crystallite size of ZrO2 and CuO/ZrO2 was 28.80 nm and 40.32 nm, respectively. Both catalysts exhibited stable crystalline forms. UV-Vis analysis showed that doping of ZrO2 with CuO significantly reduced its band gap from 4.61 eV to 1.18 eV, thus enhancing the utilization of visible light. The effect of catalyst dosage, doping ratio, and initial diesel concentration on the degradation rate of diesel was investigated by performing single-factor experiments. The optimization experiment results showed that 96.96% of diesel could be degraded under visible light. This study laid an experimental foundation for expanding the practical applications of photocatalytic technology.

Adsorption of chlortetracycline from aquaculture wastewater using modified zeolites.

In this study, lanthanum modified zeolite (La-Z) was used to adsorb chlortetracycline (CTC) from aquaculture wastewater. La-Z was characterized by SEM, TEM, EDS, XRD, FTIR and BET. The effects various factors on the adsorption of CTC by La-Z were investigated, including the lanthanum modification concentration on zeolites, the dosage of La-Z, solution pH and reaction time. Orthogonal experiments were performed to determine the optimal adsorption conditions. Adsorption kinetics were studied by quasi-first-order model, quasi-second-order model, Weber-Morris, Boyd and Bangham models, while isotherms were analyzed by the Langmuir and Freundlich models. The removal rate reached 98.4%, when the modified concentration was 0.02 mol/L, the adsorbent dosage was 0.04 g, the initial concentration of CTC was 5 mg/L, the adsorption time was 20 min, and the pH was 7. The initial CTC concentration had the greatest influence on the adsorption process. The kinetic results showed a significant linear correlation between the experimental results and the quasi-second-order kinetic model. From the results of the internal diffusion model, it was found that the La-Z adsorption rate was controlled by both internal diffusion and external diffusion, in a multi-step process. The adsorption isotherm conforms to the Langmuir model, with the maximum adsorption quantity reaching 127.55 mg/g. Thermodynamic analysis showed that the adsorption process was an endothermic process of entropy increase, which occurs spontaneously.