Hydrothermal Synthesis Of Potassium Niobate （KNbO₃） Compound And Its Study On Sonocatalytic Degradation Organic Pollutants

The ultrasonic degradation method as an Advanced Oxidation Processes （AOPs） has the potential application prospect in the field of pollutant treatment. Compared with traditional treatment methods, the degradation should be an effective way to decompose the organic dyes in non-or low-transparent effluents due to it has an advantage of having strong penetrability. Nevertheless, in actual applications, the efficacy using ultrasonic irradiation alone to degrade organic compounds is also very low. Therefore, we often used sonocatalyst in the process of sonocatalytic degradation to improve the sonocatalytic efficiency. KNbO₃ always has been considered as the most promising semiconductor material and extensively application due to its good chemical stability, high reactivity, high availability, water immiscible solvent, wide bandwidth, excellent corrosion resistance, non-toxicity, wide band gap and electrons and holes of photoproduction have very strong oxidation reduction performance. So KNbO₃ was extensive research in the field of sonocatalytic. However, KNbO₃ powder as sonocatalyst present a disadvantage. Band gap width of KNbO₃ is wide （Eg= 3.3 eV）. In the process of ultrasound catalytic reaction, only high-energy light （short wavelength light） can stimulate KNbO₃ generating electrons and holes to show sonocatalytic activity. It is regrettable that the high-energy light was a small part of sonoluminescence. It shows that the vast number of light can not be used by the KNbO₃. Therefore, KNbO₃ as sonocatalyst is limited on the application of ultrasound for the destruction of organic pollutants.In order to overcome this defect and enhance the sonocatalytic activity, on the one hand, we used up-conversion luminescence agents Er3+:Y3AlO12 to combine with KNbO₃ to enhance the sonocatalytic activity and that achieved satisfactory results. It mainly reason that the up-conversion luminescence agents can absorb two or more low-energy photons generating one high-energy photon. It can absorb the low energy light that can not directly use by KNbO₃ and then emit high energy light. On the other hand, we try to use a narrow band gap semiconductor combined with KNbO₃ to impove sonocatalytic activity. Sonoluminescence generate a part of long wavelength light can directly absorb by narrow band gap semiconductor. Due to semiconductor has a narrow band gap. Preparation composite sonocatalyst by using both approaches, it can absorb high energy light also can absorb low energy light, that is, restrain composite of photo generated electrons and holes and the photoresponse range of KNbO₃ was broaden and impove sonocatalytic activity of KNbO₃.In this study, potassium niobate （KNbO₃） powder was prepared using hydrothermal method. The up-conversion luminescence agent Er3+:Y3Al5O12, was synthesized by sol-gel method and high temperature calcinations method. The Er3+:Y3Al5O12/KNbO₃ and Er3+:Y3Al5O12/WO₃-KNbO₃ composite sonocatalysts were prepared through the ultrasonic dispersion and calcinations methods. The upconversion luminescence agent and composite sonocatalysts were characterized by X-ray diffraction （XRD）, scanning electron microscope （SEM）, energy dispersive X-ray spectroscopy （EDX） and X-ray photoelectron spectroscopy （XPS）. This paper mainly studies contents as follows:Firstly, through the ultraviolet-visible absorption spectrum calculate the degradation rate of dyes on the presence of KNbO₃ and compare those influencing factors are effect on sonocatalytic activity. Secondly, under ultrasonic irradiation Er3+:Y3Al5O12/KNbO₃ as composite sonocatalyst and application in degradation of ketamine was studied. The decomposition products of ketamine are analysed by using GC-MS machine. Thirdly, the sonocatalytic activity of prepared Er3+:Y3Al5O12/WO₃-KNbO₃ was studied through sonocatalytic degradation of methamphetamine. In addition, some influencing factors such as heat-treatment temperature, heat-treatment time, mass ratio, catalyst added, amount and ultrasonic irradiation time on the sonocatalytic activity were examined.Through the research on properties of sonocatalyst capable, we know that KNbO₃ as an effective sonocatalyst have excellent sonocatalytic activity and broad-spectrum properties to degrade organic dyes. The composite sonocatalysts were prepared through KNbO₃ combine with the up-conversion luminescence agent and narrow band gap semiconductor and applicate in sonocatalytic degradation of ketamine and methylamphetamine, to demonstrate its sonocatalytic activity. These composite sonocatalysts will have wide applications for sonocatalytic degradation organic pollutions and provided a new way to achieve large-scale dispose of pollutants.