与活化的过硫酸盐耦合的超声可以协同地降解水性有机污染物。这里,原位电子顺磁共振自旋捕获用于比较超声活化过硫酸盐(US-PS)及其各自的技术产生的自由基,单独超声(US)和热活化过硫酸盐(PS),关于温度。使用5,5-二甲基-1-吡咯啉-N-氧化物捕获自由基,DMPO,形成可检测的硝基氧加合物。使用自由基加合物形成的初始速率,与美国和PS相比,在40和50°C下的US-PS导致自由基的最大协同产生。从美国产生的自由基在40到70°C之间是合理一致的,这表明在这个范围内,温度对空化气泡破裂的影响很小。然而,从初始速率计算的协同指数表明,过硫酸盐在气泡界面的超声活化随温度而变化。从这些结果来看,我们推测,较高的温度增加过硫酸盐吸收到空化气泡通过纳米液滴注射。DMPO-OH是在所有条件下检测到的主要加合物。然而,在硝基苯和阿特拉津探针存在下的竞争建模和自旋捕获表明,SO4•-占主导地位。因此,DMPO-OH信号来源于SO4·-捕获,随后DMPO-SO4-水解为DMPO-OH。在这种情况下,自旋捕获在定量总自由基加合物形成方面是有效的,但在测量初级自由基形态方面是有限的。
Ultrasound coupled with activated persulfate can synergistically degrade aqueous organic contaminants. Here, in situ electron paramagnetic resonance spin trapping was used to compare radicals produced by ultrasonically activated persulfate (US-PS) and its individual technologies, ultrasound alone (US) and heat-activated persulfate (PS), with respect to temperature. Radicals were trapped using 5,5-dimethyl-1-pyrroline-N-oxide, DMPO, to form detectable nitroxide adducts. Using initial rates of radical adduct formation, and compared to US and PS, US-PS at 40 and 50 °C resulted in the largest synergistic production of radicals. Radicals generated from US were reasonably consistent from 40 to 70 °C, indicating that temperature had little effect on cavitational bubble collapse over this range. However, synergy indexes calculated from initial rates showed that ultrasonic activation of persulfate at the bubble interface changes with temperature. From these results, we speculate that higher temperatures enhance persulfate uptake into cavitation bubbles via nanodroplet injection. DMPO-OH was the predominant adduct detected for all conditions. However, competition modeling and spin trapping in the presence of nitrobenzene and atrazine probes showed that SO4•- predominated. Therefore, the DMPO-OH signal is derived from SO4•- trapping with subsequent DMPO-SO4- hydrolysis to DMPO-OH. Spin trapping is effective in quantifying total radical adduct formation but limited in measuring primary radical speciation in this case.