| With the increasing seriousness of population explosion, global warming and env-ironment pollution, people pay more attention to the water quality problems.In the conventional water treatment, the chlorination technology has become an irreplaceable drinking water treatment process, as it is effective, low-cost and maneuverable. However, it was revealed in the research currently that the toxicity of nitrogen disinfection by-products exceeds the carbon-containing disinfection by-products found (e.g. THMs and HAAs).Due to its strong toxicity which could affect the human neutral system, metabolism and rest immune system, nitrogen disinfection by-products gained wide public attention in the water treatment.Nitrosamine (NDMA) was widely detected in surface water at the United States and Canada as nitrogen disinfection by-products. NDMA also is a kind of carcinogenic disinfection by-products. It has been classified to2B and cancer risk coefficient will probably achieve to10-6if its exposure concentration is0.7ng/L (United States Environmental Protection Agency). From the poison rational research of NDMA as endocrine disruptors can influence human body in a long time and cause liver cancer, lung cancer and nervous system damage by its slow toxicity. So how to effectively reduce or prevent the generation of nitrosamines become more and more urgent. Removal of the NDMA has become a hot research topic which is urgent at present. In order to effectively remove NDMA in waters, firstly, the analysis of Nitrosodimethylamine in water was set up by solid-phase micro-extraction method (SPME) using gas chromatography-mass spectrometry (GC-MS). In the experiments, TiO2nanotube was prepared by anodic oxidation of titanium dioxide nanotubes as a photocatalyst. The method of fabricated TiO2nanotube was improveed by simple and rapid process and reduced the secondary pollution. SEM and XRD were used to characterize the morphology and crystalline phase of the TiO2nanotube arrays. It was found the crystal of TiO2nanotube is mix of anatase phase and rutile. The effect of different TiO2nanotube dosage, pH value, initial concentration of NDMA and dissolved oxygen were investigated in the experiments. Furthermore, low-cost and quick fabricate method of high purity potassium ferrate was prepared in this study and used as an oxidant. In this study, the oxidation efficiency of the photocatalytic oxidation in the presence of Fe(VI) was used to degrade NDMA. The effects of different initial concentration of potassium ferrate, different pH values were investigated in the experiments. The near-visible wavelength of365nm light source was used in the degradation experiments. It was found that about98%NDMA was degraded under1mg/L NDMA aqueous solution at pH=7within180min The experimental results show that the NDMA was great degraded by potassium ferrate and photocatalytic oxidation with TiO2nanotube. The major degradation products of NDMA are dimethylamine, nitrite and nitrate in this experiment. Dimethylamine is not detected within30min under the potassium ferrate oxidation. After the consumption of potassium ferrate, dimethylamine began to generate. The presence of dimethylamine, nitrite, nitrate, sodium hypochlorite will generate NDMA again. In the generate experiments, the formation of NDMA is gradually increasing with time under dark condition and constant temperature. Moreover, the generation of NDMA under neutral condition is the largest. The dose of potassium ferrate was accelerated the reaction rate and inhibits the generation of dimethylamine. Therefore, the potassium ferrate and TiO2nanotube can effectively degrade the NDMA. |
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