介质阻挡放电降解水中噻虫嗪农药的实验研究

Study on the Degradation of Thiamethoxam Pesticide in Aqueous Medium by Dielectric Barrier Discharge

利用介质阻挡放电(DBD)产生的低温等离子体可以处理水中的噻虫嗪农药。为优化采用辐流式沉淀池结构的反应器,提高噻虫嗪的降解效率,在装置内引入了负载TiO2薄膜的蜂窝陶瓷。结果表明:在500℃温度下退火能得到纯度较高的锐钛矿TiO2;改进的实验装置在放电电压75 V,噻虫嗪初始质量浓度100 mg/L的条件下,处理160 min时,噻虫嗪降解率为85.88%;装置改进后,噻虫嗪的降解速率常数提高了1.56倍,即从8.30×10-3min-1(拟合度R2=0.989 1)提高到1.30×10-2 min-1(R2=0.991 6),消耗1 kWh的能量所降解的污染物质量(能量效率)从2.39 mg增加到4.36 mg,对噻虫嗪的总有机碳(TOC)去除效率从58.83%提高到78.34%。同时电导率对放电特性的影响明显减小,为处理电导率不同的有机废水奠定了基础。此外,该装置对放电过程中化学活性物质(H2O2和O3)的形成也有促进作用。

The low temperature plasma generated by dielectric barrier discharge（DBD） helps to degrade the thiamethoxam pesticide in wastewater. To improve the DBD reactor with a structure of radial flow sedimentation tank, and to increase degradation efficiency of thiamethoxam, we introduced a honeycomb TiO2-carried ceramic into the reactor. The results show that the high purity anatase TiO2 can be obtained at an annealing temperature of 500 ℃. When the discharge voltage is 75 V and the initial concentration is 100 mg/L, treating the waste water by 160 minutes can result in a removal rate of thiamethoxam up to 85.88 %. In this case, the rate constant of the thiamethoxam degradation, the energy efficiency for thiamethoxam removal, and the TOC removal increase obviously, namely from 8.30×10-3 min-1（fitting degree R2=0.989 1） to 1.30×10-2 min-1（R2=0.991 6）, from 2.39 mg to 4.36 mg, and from 58.83 % to 78.34 %, respectively. Moreover, the impact of solution conductivity on the discharge property is reduced, which is of significance for treating wastewater of different conductivity. In addition, this set-up also benefits the formation of H2O2 and dissolved O3 in the discharge process.