光镊-受激拉曼光谱技术测量SO_(2)与悬浮NaCl单液滴的氧化反应动力学速率常数  

Investigating the Kinetic Rate Constant of SO_(2) Oxidation with Levitated NaCl Single Droplet Using Optical Tweezer-Stimulated Raman Spectroscopy

作　　者：陈哲 刘湃 庞树峰 张韫宏 CHEN Zhe;LIU Pai;PANG Shufeng;ZHANG Yunhong(School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing 10081)

机构地区：[1]北京理工大学化学与化工学院,北京100081

出　　处：《光散射学报》2022年第1期46-52,共7页The Journal of Light Scattering

基　　金：国家自然科学基金项目(41875144)。

摘　　要：硫酸盐是大气雾霾颗粒中一种重要的二次无机组分,但是有关大气硫酸盐生成机制的认识,目前还存在很多不足。同时,现有的空气质量模型也往往存在对硫酸盐生成量的低估问题,无法有效复现外场观测结果。因此,深入研究大气硫酸盐的生成机制,对理解雾霾成因、实现大气污染的精准防控具有重要意义。本研究利用光镊-受激拉曼光谱技术观测了SO_(2)与NaCl液滴的非催化氧化反应过程,液滴半径在反应过程中的纳米级变化可被精确测量,实现了反应过程的实时、原位观测。根据测定的反应速率,求算了SO_(2)氧化过程的拟一级反应速率常数k,同时研究了相对湿度、SO_(2)浓度对反应的影响。结果表明,相对湿度变化引起的液滴离子强度变化对k值具有显著影响,湿度由~60%增加至~90%时,k值下降约1个数量级。而SO_(2)浓度提升会使得液滴pH减小,导致k略微下降。对反应过程的机制讨论表明,SO_(2)在NaCl液滴中的非催化氧化过程体相反应、界面反应可能均有贡献。Sulfate is an important secondary inorganic component of haze particles,its formation mechanism,however,is still not completely clear.Besides,current air quality models often underestimate the sulfate formation amount,and cannot reproduce the field observation results successfully.Hence,it is essential to give insight into the atmospheric sulfate formation processes,which contributes to the understanding of haze formation mechanism and precise control of haze pollution.In this study,the non-catalytic oxidation process of SO_(2) with NaCl droplet was observed by optical tweezer-stimulated Raman spectroscopy.The nanoscale change of droplet radius during the reaction process can be accurately measured,so that the real-time reaction process can be in situ observed.According to the measured reaction rate,the pseudo first-order rate constant k was calculated,and the effects of relative humidity and SO_(2) concentration on the reaction were also investigated.Results showed that the change of droplet ionic strength caused by varied relative humidity significantly affected the k value.When the humidity increased from~60%to~90%,the k value decreased by an order of magnitude.As to the effect of SO_(2) concentration,increased SO_(2) concentration decreased the pH of the droplet,leading to a slight decrease in the k value.Based on the further discussion of the reaction mechanism,we found both bulk phase reaction and interface reaction may contribute to the non-catalytic oxidation of SO_(2) with NaCl droplet.

关 键 词：光镊 SO_(2) NaCl液滴 硫酸盐 非催化氧化 

分 类 号：O657.37[理学—分析化学]