Degradation and removal of environmental contaminants in water using high energy electrons and radicals

通过对1999 - 2001会计年度的研究，得出以下结果：(1)在低导电性水中，观察到水中总电击穿发展的两步击穿。这种状态的存在受到水的电导率、外加电压和存储电容器电容的限制。头部电场的畸变和由于气体通道内壁静电电荷的积累而导致的先导通道电阻的增加很可能是在瞬态状态下有效的两种机制。(2)随着电极间隙距离的变化，可以观察到三种放电模式，即流光放电、带流光放电和火花放电。活性物质的形成和紫外线辐射是有机污染物降解的重要化学物质和物理效应，它们强烈依赖于排放方式。(3)发现放电方式、鼓泡气体和化学添加剂对苯酚和染料的降解有影响。在流光放电的情况下，羟基自由基被认为是主要的过程。在火花放电和火花流放电模式下，除羟基自由基外，还会对降解过程产生冲击波和紫外线等物理效应。(4)环形电极周围产生大体积流线型电晕放电，放电的形成与电极的几何形状、极性和水的电导率有很大关系。研究发现，环形电极的绝缘技术是降低流线起始电压的最重要因素。

The following results were obtained as the research from 1999 to 2001 fiscal years.(1) In low conductive water, two-step breakdown in the development of the total electrical breakdown in water were observed. The existence of this regime was limited by the water conductivity, applied voltage, and capacitance of the storage capacitor. The distortion of the electric field at the head and an increase of the leader channel resistance due to accumulation of the electrostatic charge on inside wall of the gaseous channel were most likely two mechanisms effective in the transient regime.(2) With changing electrode gap distance, three discharge modes were observed, i.e. streamer, spark with streamer, and spark discharges. The formation of active species and ultraviolet radiation, which are important chemical species and physical effects for degradation of organic pollutants were strongly dependent on the discharge mode.(3) It was found that the discharge modes, gas bubbling and chemical additives affected the degradation of phenol and dyes. In the case of streamer discharge, hydroxyl radicals were considered to be the dominant process. In the case of spark and spark with streamer discharge mode, the other physical effects such as shockwave and ultraviolet radiation may take place on the degradation process besides the hydroxyl radicals.(4) A large volume streamer corona discharge was generated around the ring electrode, and the discharge formation was greatly dependent on the electrode geometry, polarity and the water conductivity. It was found that the insulation technique of the ring electrode was the most important factor for decrease streamer initiation voltage.