Study On Preparation Of N, F-codoped TiO₂Nanoparticles And Degradation Of Azo Dye Under Visible Light

With the development of modern industry, a large number of azo dye wastewaterdischarge into the water, causing serious pollution of water environment. Azo dye is akind of aromatic compounds. When azo dye wastewater released into the water, ithave chemical stability and make prone to eutrophication. So it is a typical refractoryorganic pollutants. Azo dye wastewater treatment is a research hotspots and thedifficulty in the environment field. In recent years, TiO2Semiconductorphotocatalytic technology is widely used in the dye wastewater treatment. TiO2photocatalysis technology will be a research trend in the field of water treatment.But TiO2as photocatalyst has two problems: one is TiO2with a band gap of3.2eV can be photoexcited under irradiation of UV light (λ<387.5nm) which limits thepractical applications due to the poor utilization of solar lights. Secondly, due to thehigher recombination rate of electronic (e-) and holes (h+), the low quantumefficiency, the photocatalytic efficiency of TiO2was also influenced. So, considerableeffort has been made to improve photocatalytic activity of TiO2through varioussurface modifications such as doping of various metal or nonmetal oxides.The preparation of N, F-codoped TiO2and TiO2nanoparticle as photocatalystswith hydrothermal methods at room temperature was proposed. The effects ofselected process parameters such as molar ratio of nitrogen (N) or fluorine (F) and Ti,hydrothermal time and temperature, initial concentration of methyl orange solution,irradiation time, catalyst dose, and light power on their photocatalytic performanceunder visible light were assessed in detail, which using methyl orange as modelcompounds. The result showed that N-F-TiO2has the hightest photocatalytic activityfor degradation of10mg/L methyl orange. When irradiation time is4h, degradationrate is up to100%. The degradation rate of10mg/L methyl orange is87.3%in thepresence of TiO2. We also use liquid chromatography and ion chromatography todetecte the degradation products of different time. The results show that most methylorange molecules could be effectively degraded and almost mineralized to simpleinorganic ions. The3.5h degradation sample of methyl orange solution was analyzed using LC-MS. The experiments show that the degradation may have intermediateproducts in the process.The preparation of Fe-N-F-TiO2, Co-N-F-TiO2and Ni-N-F-TiO2nanoparticle asphotocatalysts with hydrothermal methods at room temperature was proposed. Theeffects of selected process parameters such as molar ratio of Iron(Fe), cobalt(Co) ornickel(Ni) to Ti, hydrothermal temperature and time, irradiation time on theirphotocatalytic performance under visible light were assessed in detail using acidorange Ⅱ as a model contaminant in aqueous solution. The results showed thatNi-N-F-TiO2has hightest photocatalytic activity for degradation of10mg·L-1acidorange Ⅱ, when irradiation time is2.5h, degradation rate is up to100%. Thedegradation rate of acid orange Ⅱ is93.55%in the presence of Fe-N-F-TiO2. Thedegradation rate of acid orange Ⅱ is89.77%in the presence of Co-N-F-TiO2. Wealso use liquid chromatography and ion chromatography to detecte the degradationproducts. The results show that most acid orange Ⅱ molecules could be effectivelydegraded and almost mineralized to simple inorganic ions.