介质阻挡放电脱色酸性橙Ⅱ废水的动力学及脱色物化效应

Kinetic and Physiochemical Effects of Decolorization of AO7 Dye Wastewater by DBD

气-液两相介质阻挡放电（DBD）等离子体对废水电导率较不敏感,因此电极施加电压和放电气隙成为影响放电强度及废水中污染物降解的两个主要因素。以酸性橙Ⅱ（AO7）废水为对象,考察了电极施加电压、放电气隙等因素对DBD装置放电特性及AO7降解动力学的影响,分析了DBD降解AO7的主要物化效应。结果表明：高压电极引发的丝状放电通道随电压升高、放电气隙减小而增多,且丝状放电通道在接近液面时出现明显的分支现象;AO7降解符合一级反应动力学,施加电压升高、放电气隙减小可提高AO7降解的反应动力学常数。放电气隙为6 mm,峰值电压从15 kV分别升高2 kV和4 kV,反应动力学常数可提高4.45倍和5.67倍;电极施加电压为17 kV,放电气隙从8 mm减小到4 mm和2 mm,AO7降解的反应动力学常数可分别提高3.51倍和6.67倍。废水的pH值对AO7降解也有较大影响,酸性条件和碱性条件下AO7降解的反应动力学常数较大。分析DBD等离子体降解AO7的物理化学效应,臭氧和过氧化氢等反应活性物质是AO7降解的主要原因。

The conductivity of wastewater has little effect on the generation of hybrid gas/liquid dielectric barrier discharge（DBD）, so the voltage applied on high-voltage electrode and the air discharge gap are two very important factors which influence the degradation of aqueous pollutants. We investigated the effect of applied voltage, air discharge gap, etc. on the discharge characteristics of DBD reactor and the degradation kinetics of acid orange Ⅱ（AO7）, and analyzed the physiochemical effects responsible for AO7 degradation. The results indicate that the number of discharge filaments initiated from the high voltage electrode increases with the applied voltage, but decreases with the air discharge gap（s）; moreover, some branches appear on the filamentous discharge channels when they are near the water surface. AO7 follows a pseudo first-order degradation kinetics, and the reaction kinetic constants increase with the applied voltage, but decrease with the air discharge gap. At an air discharge gap of 6 mm, the reaction kinetic constant is increased by about 4.45 times and 5.67 times when the applied voltage increases to 17 kV and 19 kV from 15 kV, respectively. At an applied voltage of 17 kV, the reaction kinetic constant at s of 4 mm and 2 mm is 3.51 times and 6.67 times that at s of 8 mm, respectively. The p H value of wastewater also influences the degradation of AO7, and it is found that AO7 degrades faster in acidic or basic wastewater than in neutral or nearly neutral condition. Experimental analyses show that the reactive species, including ozone and hydrogen peroxide, the important physiochemical effects produced from DBD plasma, are responsible for AO7 degradation.