| As the main organic components in nature water body, humic acid (HA) has brought a great influences on the health of human beings and the environment. It is reported that HA affects the enrichment, migration of metal ions and trace element. As a result, the toxicity of nature water increased little by little. In addition, it has been confirmed that humic substances are the major precursors of disinfectant by-products during chlorination disinfection and trichloromethane class carcinogenic substance. However, humic acid is difficult to treatment by traditional biodegradation method, and it is not satisfied with the natural degradation.Photocatalytic degradation processes have been widely applied as techniques of destruction of organic pollutants in waste water. With an appropriate light irradiation, the photocatalyst generates electron/hole pairs with free electrons produced in the empty conduction band leaving positive holes in the valence band. These electron/hole pairs are capable of initiating a series of chemical reactions that eventually mineralize the pollutants.A series of zinc titanate nanoparticles was successfully synthesized using a simple sol-gel technique. The composites were characterized by thermogravimetric and differential thermal analysis (TG-DTA), X-ray diffraction (XRD) patterns, scanning electron microscope (SEM), energy dispersive spectrometer (EDS), X-ray photoelectron spectra (XPS) and UV-vis diffuse reflectance spectra (UV-vis). The photocatalytic activity of samples was investigated by degradation of humic acid (HA) in water under sunlight and xenon light irradiation. The sample calcined at 800℃was found to exhibit much higher photocatalytic activity than the other samples. The investigation of photocatalytic mechanism indicates that the holes (h+) and·OH radicals may be the major reactive species for the degradation of HA. Meanwhile, the processing parameters such as the light source and the dosage of catalysts play an important role in tuning the photocatalytic activity. Under sunlight irradiation, the humic acid of photocatalytic degradation was 100% after 1.5 h with the dosage of photocatalysts was 0.8 g/L. The enhancement of photocatalytic activity for the zinc titanate nanoparticles calcined at 800℃may be attributed to the smaller particle size, higher redox ability and coordination of Ti ions.The powders of ilmenite structure NiTiO3 were prepared by a modified Pechini process using tetrabutyl titanate and nickel acetate as raw material, citric acid and ethanol as the chelating agent and the solvent. The powder samples were characterized by thermogravimetric and differential thermal analysis (TG-DTA), X-ray diffraction (XRD) patterns, scanning electron microscope (SEM), energy dispersive spectrometer (EDS), UV-vis diffuses reflectance spectra (UV-vis). The photocatalytic activity of NiTiO3 under the irradiation of UV-light was evaluated by degrading the humic acids (HA) in water as a probe reaction. The thermal analytic and XRD results indicated that the good crystal structures of ilmenite phase NiTiO3 can be obtained when the Ni-Ti citrate complex was calcined at about 600℃, The UV-vis analysis indicated that the band energy of NiTiO3 sample calcined at 600℃is about 2.15 eV. The photocatalytic activity experiments indicated that the NiTiO3 had favourable photocatalytic activity under the irradiation of UV-light, the photocatalytic degradation rate of humic acid was reached 95.3% after 2.5 h reaction with the photocatalyst calcined at 600℃and the photocatalyst dosage of 0.4 g·L-1. |
PDF Full Text Request