高压脉冲气-液同步放电降解甲基红

Degradation of methyl-red in pulsed high-voltage reactor byliquid-gas synchronous discharge

实心、细直径的针灸针穿过曝气小孔中心轴线到达高压脉冲放电反应器反应室底部,在针的周围曝气,使针电极包围在气体氛围中,并把接地极板置于液面之上,形成气 液间歇式同步放电.实验表明,在一定条件下,液体内部,尤其是液面会有不同程度的能量聚积,从而导致液下放电电极针尖周围、液面和接地极板气层之间同步间歇式火花放电,并伴随不同程度的冲击波和强烈的紫外光.脉冲峰压的升高、电极距离的缩短、脉冲频率的加大致使甲基红的降解速率增加.在脉冲峰压为20kV、电极距离为18mm、脉冲频率为150Hz条件下,放电30min,甲基红的降解率约为99%.甲基红在高压脉冲反应器内的降解属于自由基反应,其分子结构的破坏源于偶氮键的破裂,主要的中间产物是对硝基 N,N 二甲基苯胺、甘油以及少量的对硝基苯酚和微量的甘氨酸 N 羧甲基.

Acupuncture needles used as discharge electrodes were placed through the axial cord of microtubules to the bottom of the reaction chamber in pulsed high-voltage discharge reactor. The needles were surrounded by the gas aerated through the microtubules and the ground plate was placed over the liquid level. When pulsed high-voltage was applied to the electrodes, intermittent gas-liquid synchronous discharge occurred, which was induced by the energy gathering in liquid, especially the liquid level. The discharge was accompanied by intense shake wave and light. The methyl-red degradation was sped up by shortening the distance between the electrodes or increasing the peak voltage or frequency. Excess salt of certain KC1 caused a decrease in the degradation rate. Removal rate of 99% for methyl-red was obtained after 30 min discharge at 20 kV of peak voltage, 150 Hz of frequency and 18 mm of distance. The degradation is due to radical reaction and one of the structure destruction routes is induced by the break of the azo bond. The main intermediate products are N, N-dimethy-l-4-nitrobenzene, paranitrophenol, glycerine and glycine-N-carboxymethyl.