论文部分内容阅读
通过超声动力学分析与实验相结合的研究方法,阐述了超声波促进农药溶解和引发农药分解两种效应的内在机理和相互制约关系。首先,基于Rayleigh-Plesset方程,利用数值迭代法(龙格-库塔算法)计算不同能量和频率组合下超声波的空化效应类型及强度;然后,进行纯溶剂中农药的分解率实验和菠菜基质中农药的回收率实验。研究结果表明:超声波的瞬态空化效应一方面通过破坏植物组织,促进被吸附的农药的释放,另一方面产生羟自由基(-OH)等游离子,导致农药被氧化分解。瞬态空化效应的强弱可通过单位时间内空化泡崩溃释放的压力值(Pmax/t)直观表示,当Pmax/t≤2.1×107atm/s时,溶解效应强于分解效应,农药回收率随Pmax/t增大而增大;当Pmax/t>2.1×107atm/s时,分解效应大于溶解效应,回收率降低;9种农药的平均回收率在Pmax/t=2.1×107atm/s时达最高值(此时超声波的频率和能量分别为45kHz和400W),可实现菠菜中多残留农药高溶解、低分解的超声萃取。
Through the research methods of combining ultrasonic dynamic analysis and experiment, the internal mechanism and mutual restraint relationship of two kinds of effects of ultrasound on pesticide dissolution and pesticide decomposition are described. Firstly, based on the Rayleigh-Plesset equation, the numerical iteration method (Runge-Kutta algorithm) was used to calculate the type and intensity of cavitation effect under different energy and frequency combinations. Then, the degradation rate of pesticides in pure solvent and spinach matrix Pesticide recovery experiments. The results show that the transient cavitation effect of ultrasonic wave can promote the release of adsorbed pesticides, on the one hand, and destroy the free radicals of hydroxyl radicals (-OH), on the other hand, resulting in the decomposition of pesticides. The strength of transient cavitation effect can be directly expressed by the pressure value (Pmax / t) released by cavitation bubble collapse per unit time. When Pmax / t≤2.1 × 107atm / s, the dissolution effect is stronger than the decomposition effect and the pesticide recovery When the Pmax / t> 2.1 × 107atm / s, the decomposition effect was greater than the dissolution effect, the recovery rate decreased; the average recovery rate of nine pesticides was at Pmax / t = 2.1 × 107atm / s When the highest value (the frequency and energy of ultrasonic at this time were 45kHz and 400W), spinach can be more residual pesticides dissolved, low decomposition of ultrasonic extraction.