| Nuclear energy developments and their utilizations, such as nuclear fuel cycle, nuclear power plants operation and nuclear facilities decommissioning, would produce a large amount of radioactive organic wastewater. Organics are unfavorable in the storage of radioactive wastewater, due to that they will increase the difficulties of waste liquid disposal and have adverse effects on the wastewater disposal. In recent years, photocatalytic oxidation technologies have become the focus in the organic wastewater treatment with its environmentally friendly, mild reaction conditions, stable chemical properties. Nevertheless, the works on the photocatalytic oxidation degradation of organic s in radioactive wastewater research are rarely seen in literatures. For this reason, this thesis is then focused on the doping and modification of Ti O2 nanotubes(TNTs) and trying to use them into the photodegradation of tannic acid and adsorption of Sr2+ and Cs+ in simulated radioactive wastewater treatment.Specific research contents and results are as follows:(1) A series of TNTs with high crystallinity and unified morphology were successfully synthesised by varying the precursor concentration, reaction temperature, and reaction time during the hydrothermal procedure in Na OH(10 M) solution. We explored the best synthesis conditions for TNTs productions, and investigated the influences of hydrothermal conditions on the morphology of TNTs. The results showed that the as-prepared TNTs are with pipe diameter of about 10 nm, and the length about 300 nm.(2) The Fe, N co-doped TNTs(Fe/N-TNTs) were successfully synthesized by adding ferric nitrate nonahydrate and urea in precursors under the best hydrothermal conditions. The photocatalytic activities of the prepared photocatalysts were measured under visible light irradiation for photodegradation of tannic acid. The result indicated that the as-prepared doping TNTs were nanotublar structures, with mixed crystal structures of anatase and rutile. The doped TNTs exhibited enhanced visible photocatalytic activity. The Fe/N-TNTs with initial concentration of ferric nitrate nonahydrate(3 wt.%) and urea(25 wt.%) exhibited the highest activity for tannic acid photodegradation under visible light irradiation.(3) The effects of gamma irradiations in a range of 2.48 k ~ 20.20 k Gy on the 3Fe/N-TNTs were characterized. We introduced Sr2+ and Cs+ in the tannic acid solution to study the effects of nuclide on the photodegradation of tannic acid. The photocatalytic activities were analysed after irradiations. The results showed that under 2.48 k ~ 20.20 k Gy gamma irradiations the morphology and structure of the Fe/N-TNTs were not obviously affected. However, the irradiated 3Fe/N-TNTs exhibited slightly reduced photocatalytic activities under visible light irradiations. Our investigations indicated that both of the Sr2+ and Cs+ have no obvious effect on photodegradation of tannic acid under visible light irradiation.(4) Cr doped TNTs were synthesized by the hydrothermal method, and it was used to adsorb Sr2+ and Cs+ from wastewater. The results showed that the Cr doping would improve the adsorption property of TNTs, and the adsorption capacity for Sr2+ and Cs+ was 12 and 16 mg/g, respectively. 2 M NH4NO3 was used to desorption and the Cr-doped Ti O2 nanotubes exhibited good cycle performance after 5 cycles and only droped to near 80%.We believe that our research would have contributions on the improvment of photocatalytic activity for Ti O2, further extending the applications, and relieving the burdens on the way to the engineering applications of radioactive organic wastewater treatment. |
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