Photochemical Reactions of Glyoxal during Particulate Ammonium Nitrate Photolysis: Brown Carbon Formation, Enhanced Glyoxal Decay, and Organic Phase Formation

Ruifeng Zhang ◽  
Masao Gen ◽  
Zhancong Liang ◽  
Yong Jie Li ◽  
Chak Keung Chan
Hind A. A. Al-Abadleh

Extensive research has been done on the processes that lead to the formation of secondary organic aerosol (SOA) including atmospheric oxidation of volatile organic compounds (VOCs) from biogenic and anthropogenic...

2020 ◽  
Vol 54 (20) ◽  
pp. 13207-13216
Nethmi Y. Kasthuriarachchi ◽  
Laura-Hélèna Rivellini ◽  
Xi Chen ◽  
Yong Jie Li ◽  
Alex K. Y. Lee

2019 ◽  
Michael Servis ◽  
David T. Wu ◽  
Jenife Shafer ◽  
Aurora Clark

Liquid/liquid phase transitions are inherent to multicomponent solutions, which often contain a diversity of intermolecular interactions between their molecular constituents. In one such example, a phase transition is observed in liquid/liquid extraction where the nonpolar organic phase separates into two phases under sufficiently high metal and acid extraction by the amphiphilic extractant molecule. This deleterious phenomenon, known as third phase formation, complicates processing and limits efficiency. While empirically well documented, the molecular origin of this phenomenon is not understood. The prevailing conceptualization of the organic phase treats it as a microemulsion where extractant molecules form reverse micelles that contain the extracted aqueous solutes in their polar cores. Yet recent studies indicate that a microemulsion paradigm is insufficient to describe molecular aggregation in some solvent extraction systems, implying that an alternative description of aggregation, and explanation for third phase formation, is needed. In this study, we demonstrate that the formation of a third phase is consistent with crossing the liquid-liquid miscibility gap for a molecular solution rather than a Winsor II to Winsor III transition as presumed in the microemulsion paradigm. This insight is provided by using a graph theoretic methodology, generalizable to other complex multicomponent molecular solutions, to identify the onset of phase splitting. This approach uses connectivity obtained from molecular dynamics simulation to correlate the molecular-scale association of extractants and extracted solutes to the solution phase behavior using percolation theory. The method is applied to investigate a solvent extraction system relevant to ore purification and used nuclear fuel recycling: tri-n-butyl phosphate/uranyl nitrate/water/nitric acid/n-dodecane. In analogy to a molecular solution, immediately preceding the liquid-liquid coexistence curve from the single phase region, the metal-ligand complexes percolate. This demonstrates that describing this solution with microemulsion chemistry is neither applicable nor broadly required to explain third phase formation. Additionally, the method developed herein can predict third phase formation phase boundaries from simulation for this and potentially other solvent extraction systems.

2019 ◽  
Vol 6 (3) ◽  
pp. 184-190 ◽  
Huanhuan Jiang ◽  
Alexander L. Frie ◽  
Avi Lavi ◽  
Jin Y. Chen ◽  
Haofei Zhang ◽  

2020 ◽  
David O. De Haan ◽  
Lelia N. Hawkins ◽  
Kevin Jansen ◽  
Hannah G. Welsh ◽  
Raunak Pednekar ◽  

Abstract. Alpha-dicarbonyl compounds are believed to form brown carbon in the atmosphere via reactions with ammonium sulfate (AS) in cloud droplets and aqueous aerosol particles. In this work, brown carbon formation in AS and other aerosol particles was quantified as a function of relative humidity (RH) during exposure to gas-phase glyoxal (GX) in chamber experiments. Under dry conditions (RH 

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