烟梗生物炭持久性自由基反应活性的比较

Comparison of reactivity of persistent free radicals on tobacco stem biochar.

本研究选用不同热解温度(300,500和700°C)制备的烟梗生物炭,与有机污染物对硝基苯酚(PNP)进行吸附降解反应,探究反应前后烟梗生物炭上持久性自由基(EPFRs)信号强度与其降解有机污染物活性的关系.结果显示:生物炭中EPFRs信号强度随热解温度的升高而从6.155×10^4升高至1.343×10^5后降低至5.458×10^4,而PNP的液相降解率则表现为随热解温度的升高先保持为31%左右不变后下降至14.64%,表明生物炭的EPFRs信号强度与活性并不成正比.300℃热解制备的生物炭中以氧为中心的自由基可以将电子转移给水中的氧分子生成活性氧并促进PNP的降解.而500与700℃热解制备的生物炭中碳为中心的自由基与污染物进行降解反应后生成了新的自由基并被稳定于生物炭表面,导致其自由基信号增强降解活性却大幅下降.

In this study,tobacco stem biochar prepared at different pyrolysis temperatures(300℃,500℃and 700℃)was used for the adsorption and degradation of organic pollutants p-nitrophenol(PNP).The aim of this research was to explore the relationship between the intensity of environmental persistent free radicals(EPFRs)on tobacco stem biochar and its reactivity towards organic pollutants degradation.The results showed that the intensity of EPFRs in the tobacco stem biochar increased from 6.155×10^4 to 1.343×10^5 at first and then declined to 5.458×10^4 with the increase of pyrolysis temperature,while the degradation rate of PNP remained unchanged at around 31%and then declined to 14.64%with the increase of pyrolysis temperature.These phenomena indicated that the intensity of EPFRs in biochar was not directly correlated to its reactivity.The oxygen-centered EPFRs in biochar pyrolyzed at 300℃could transfer electrons to oxygen molecules in the water and generate reactive oxygen species(ROS),thus promote the degradation of PNP.The carbon-centered EPFRs in biochar pyrolyzed at 500℃and 700℃could be consumed after reacting with water or pollutants,and the newly generated free radicals were stabilized on the surface of biochar,which led to a significant increase in their intensity but their degradation activity declined dramatically.