Abstract：A combination of vacuum FTIR spectrometer (Vertex 80v, Bruker, German) and novel relative humidity (RH) adjusting equipment,which provides the pressure by pure water vapor, is used to study the hygroscopicity of magnesium acetate (Mg(CH3COO)2) aerosols. The RH can change not only rapidly but also slowly by the RH adjusting equipment.Because the RH is decided by the pure vapor, the real-time RH can be gained by calculating the integrated intensity of a feature band of vapor in an IR spectrum. Such the synchronism between FTIR spectrum and RH canbe ensured.The high-quality spectra of aerosols are obtained and the water peak and feature peaks of Mg(CH3COO)2 are analyzed during the slow and rapid RH changing process.The result shows that the areas of acetate ions and water decreases continuously at constant high RHs. After a slow cycle of RH (1.05×104 minutes), the water area decreases from 1.5 to 1.1, which means that the water content decreases after a cycle of RH. This phenomenon is reported at first up to date. The detailed analysis suggests that the hydrolysis of Mg(CH3COO)2 at high RH produces acetic acid, which was put out from the aerosols owing to the decrease of the pressure around the aerosols droplets. Furthermore, the dynamic hygroscopicity of Mg(CH3COO)2 aerosols is studied by changing RH as a pulse mode. It reveals that there is only water transfer hysteresis and no water loss after a pulse (10 seconds) when the RH is above 70%. Compared to slow process, it can be concluded that the hydrolysis reaction rate is slower than that of a pulse RH. The water transfer limited on rapid process should rise from some species on the surface of aerosols.
Key words：Magnesium acetate aerosol;Water transfer process;Evaporation
王 娜，庞树峰*，张韫宏. 利用不同的湿度调节方法研究醋酸镁气溶胶中水的传质过程[J]. 光谱学与光谱分析, 2016, 36(05): 1581-1584.
WANG Na, PANG Shu-feng*, ZHANG Yun-hong. Study on the Water Transfer of Magnesium Acetate Aerosols Led by the Rapid and Slow Change of Relative Humidity. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2016, 36(05): 1581-1584.
[1] Charlson R J, Schwartz S E, Hales J M, et al. Science, 1992, 255(5043): 423. [2] Kwamena N O A, Buajarern J, Reid J P. Journal of Physical Chemistry A, 2010, 114(18): 5787. [3] Shi Y J, Ge M F, Wang W G. Atmospheric Environment, 2012, 60: 9. [4] Minambres L, Mendez E, Sanchez M N, et al. Atmospheric Environment, 2013, 70: 108. [5] Ghorai S, Wang B B, Tivanski A, et al. Environmental Science & Technology, 2014, 48(4): 2234. [6] Maskey S, Chong K Y, Kim G, et al. Particuology, 2014, 13: 27. [7] Lu J W, Rickards A M J, Walker J S, et al. Physical Chemistry Chemical Physics, 2014, 16(21): 9819. [8] Chan M, Chan C. Atmospheric Chemistry and Physics, 2005, 5(10): 2703. [9] Li K K, Wang F, Zeng G, et al. Journal of Physical Chemistry B, 2011, 115(49): 14397. [10] Martin S T. Chemical Reviews, 2000, 100(9): 3403. [11] Zobrist B, Marcolli C, Pedernera D A, et al. Atmospheric Chemistry and Physics, 2008, 8(17): 5221. [12] Huffman J, Docherty K, Aiken A, et al. Atmospheric Chemistry and Physics, 2009, 9(18): 7161. [13] Tong H J, Reid J P, Bones D L, et al. Atmospheric Chemistry and Physics, 2011, 11(10): 4739. [14] Pang S, Wu C, Zhang Q, et al. Journal of Molecular Structure, 2015, doi: 10.1016/j.molstruc.2015.01.034. [15] Wang L Y, Zhang Y H, Zhao L. J. Journal of Physical Chemistry A, 2005, 109(4): 609. [16] Shulman M L, Charlson R J, Davis E. J. Journal of Aerosol Science, 1997，28(5): 737.
