Student BIOS

CHU Yangxi

PhD in Environmental Science, Policy and Management - 2017

B.E. in Environmental Science and Engineering, University of Science and Technology of China

Supervisor:  Prof. CHAN Chak Keung       Co-Supervisor: Prof. CHAN Chi Ming

Research Topic  
Role of organics in mixture with ammonium/aminium sulfate particles in ammonia–amine exchange reactions
Amine; Ammonia; Hygroscopicity; Viscosity; Particle phase

Amines are organic nitrogen compounds and the most important category of alkaline gases besides ammonia in the atmosphere. They have been ubiquitously detected in both gas and particle phases, among which short-chain aliphatic amines are the most common and abundant species. Due to insufficiency of experimental data, physical and chemical characteristics and the atmospheric behavior of amines are still not well understood.

In this study, the hygroscopic properties of atmospherically relevant alkyl aminium sulfates are firstly investigated using air-flow cell. Samples are synthesized by mixing sulfuric acid with each of the individual aqueous amine solutions, and characterized by in situ micro-Raman spectroscopy. Normalized Raman peak area of water signals in the Raman spectra is converted to water-to-solute mole ratios (WSR) at different relative humidity (RH). Phase transition of alkyl aminium sulfates during the humidity cycles is recorded by microscope imaging and indicated from the Raman spectra. In parallel with the hygroscopic measurements, chemical compositions of the aminium sulfate salts have been determined by off-line ion chromatography.

Based upon the findings that phases of single particle containing ammonium/aminium sulfate can significantly affect the degree of ammonium/aminium displacement by amine/ammonia vapor uptake, role of the phase state of organics in mixture with particulate ammonium/aminium sulfate salts on the ammonium–amine exchange reactions will be evaluated. Characterization techniques involve the electrodynamic balance (EDB) coupled with Raman spectroscopy.

Journal Publication
Yangxi Chu, Meike Sauerwein and Chak K. Chan (2015) Hygroscopic and phase transition properties of alkyl aminium sulfates at low relative humidities. Physical Chemistry Chemical Physics, 17, 19789-19796.
Yangxi Chu and Chak K. Chan (2017) Reactive Uptake of Dimethylamine by Ammonium Sulfate and Ammonium Sulfate−Sucrose Mixed Particles. The Journal of Physical Chemistry A, 121, 206-215.
Conference Paper
Yangxi Chu, Meike Sauerwein, Chak K. Chan (2015) Hygroscopic Properties of Four Alkyl Aminium Sulfates at Low Relative Humidity Using Micro-Raman Spectroscopy, 9th Asian Aerosol Conference, Japan.
Yangxi Chu, Meike Sauerwein, Chak K. Chan (2015) Hygroscopic Properties of Alkyl Aminium Sulfates at Low Relative Humidities (RH), American Association for Aerosol Research (AAAR) 34th Annual Conference, United States of America.
Yangxi Chu and Chak K. Chan (2016) Role of sucrose in the heterogeneous uptake of dimethylamine by ammonium sulfate aerosol particles, 2016 American Geophysical Union (AGU) Fall Meeting, United States of America.
Title Date Length Type and Location
Study of Hygroscopic Characteristics of Aminium Sulfate Particles by Using Optical Microscope and Raman Spectroscopy 2014-03-20 30 min ENVR Postgraduate Seminar
Role of organics in mixture with ammonium/aminium sulfate particles in ammonia–amine exchange reactions 2015-04-16 50 min PhD Qualifying Examination Oral Defense
Heterogeneous uptake of short-chain alkyl amine by atmospherically relevant particles 2016-10-29 15 min Workshop on Photochemical Smog in China at HKUST campus
Teaching Assistant
Semester Course Code Course Title Class Size
2013-14 Spring ENVR 3310 Green Business Strategy 40
2014-15 Fall ENVR/CHEM 5410 Atmospheric Chemistry 20
2015-16 Fall ENVR 2010 Environmental Science Fundamentals 40
2015-16 Spring ENVR 3410 Economics for Environmental Policy and Management 40
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