scholarly journals A quantitative property-property relationship for the internal diffusion coefficients of organic compounds in solid materials

Indoor Air ◽  
2017 ◽  
Vol 27 (6) ◽  
pp. 1128-1140 ◽  
Author(s):  
L. Huang ◽  
P. Fantke ◽  
A. Ernstoff ◽  
O. Jolliet
Keyword(s):  
Organic Compounds ◽  
Diffusion Coefficients ◽  
Internal Diffusion ◽  
Solid Materials ◽  
Property Relationship ◽  
Quantitative Property

Diffusion coefficients and viscosities of organic aerosol components through equilibrium and non-equilibrium molecular dynamics simulations

2021 ◽  
Author(s):  
Katerina S. Karadima ◽  
Vlasis G. Mavrantzas ◽  
Spyros N. Pandis
Keyword(s):  
Molecular Dynamics ◽  
Functional Groups ◽  
Organic Compounds ◽  
Diffusion Coefficients ◽  
Amorphous Solid ◽  
Good Effect ◽  
Hydroxyl Groups ◽  
Chemical Structures ◽  
Organic Particles ◽  
Non Equilibrium

<p>Organic aerosols have been typically considered to be liquid, with equilibration between gas and aerosol phase assumed to be reached within seconds. However, Virtanen et al. (Nature, 2010) suggested that particles in amorphous solid state may also occur in the atmosphere implying that mass transfer between the atmospheric particulate and gas phases may be much slower than initially thought. Experimentally, the direct measurement of the diffusion coefficients of different compounds inside atmospheric organic particles is challenging. Thus, an indirect approach is usually employed, involving viscosity measurements and then estimation of diffusion coefficients via the Stokes-Einstein equation, according to which the diffusion coefficient is inversely proportional to the medium viscosity. However, the corresponding diffusion estimates are highly uncertain, especially for highly viscous aerosols which is the most important case. Molecular simulation methods, such as molecular dynamics (MD), can be an alternative method to determine directly the diffusion rates and the viscosity of the constituents of atmospheric organic particles. MD also provides detailed information of the exact dynamics and motion of the molecules, thus offering a deeper understanding on the underlying mechanisms and interactions.</p><p>In the present work, we use equilibrium and non-equilibrium MD simulations to estimate the viscosity and diffusion coefficients of bulk systems of representative organic compounds with different chemical structures and physicochemical characteristics. Hydrophilic and hydrophobic compounds representative of primary and secondary oxidized organic products and of primary organic compounds emitted by various sources are considered. The viscosity and self-diffusion coefficients calculated by our simulations are in good agreement with available experimentally measured values. Our results confirm that the presence of carboxyl and hydroxyl groups in the molecule increases the viscosity. The number of carboxyl and hydroxyl groups, in particular, seems to have a good effect on diffusivity (the diffusivity decreases as the number of these functional groups increase), and to a lesser extent on the viscosity. We also discuss the role of the hydrogen bonds formed between these functional groups.</p>

scholarly journals Kinetic modeling studies of SOA formation from <i>α</i>-pinene ozonolysis

2017 ◽  
Vol 17 (21) ◽  
pp. 13187-13211 ◽  
Author(s):  
Kathrin Gatzsche ◽  
Yoshiteru Iinuma ◽  
Andreas Tilgner ◽  
Anke Mutzel ◽  
Torsten Berndt ◽  
...  
Keyword(s):  
Diffusion Coefficient ◽  
Organic Compounds ◽  
Diffusion Coefficients ◽  
Bulk Diffusion ◽  
Organic Aerosol ◽  
Successful Implementation ◽  
Particle Phase ◽  
Organic Mass ◽  
Model Framework ◽  
Aerosol Mass Concentration

Abstract. This paper describes the implementation of a kinetic gas-particle partitioning approach used for the simulation of secondary organic aerosol (SOA) formation within the SPectral Aerosol Cloud Chemistry Interaction Model (SPACCIM). The kinetic partitioning considers the diffusion of organic compounds into aerosol particles and the subsequent chemical reactions in the particle phase. The basic kinetic partitioning approach is modified by the implementation of chemical backward reaction of the solute within the particle phase as well as a composition-dependent particle-phase bulk diffusion coefficient. The adapted gas-phase chemistry mechanism for α-pinene oxidation has been updated due to the recent findings related to the formation of highly oxidized multifunctional organic compounds (HOMs). Experimental results from a LEAK (Leipziger Aerosolkammer) chamber study for α-pinene ozonolysis were compared with the model results describing this reaction system.The performed model studies reveal that the particle-phase bulk diffusion coefficient and the particle-phase reactivity are key parameters for SOA formation. Using the same particle-phase reactivity for both cases, we find that liquid particles with higher particle-phase bulk diffusion coefficients have 310 times more organic material formed in the particle phase compared to higher viscous semi-solid particles with lower particle-phase bulk diffusion coefficients. The model results demonstrate that, even with a moderate particle-phase reactivity, about 61 % of the modeled organic mass consists of reaction products that are formed in the liquid particles. This finding emphasizes the potential role of SOA processing. Moreover, the initial organic aerosol mass concentration and the particle radius are of minor importance for the process of SOA formation in liquid particles. A sensitivity study shows that a 22-fold increase in particle size merely leads to a SOA increase of less than 10 %.Due to two additional implementations, allowing backward reactions in the particle phase and considering a composition-dependent particle-phase bulk diffusion coefficient, the potential overprediction of the SOA mass with the basic kinetic approach is reduced by about 40 %. HOMs are an important compound group in the early stage of SOA formation because they contribute up to 65 % of the total SOA mass at this stage. HOMs also induce further SOA formation by providing an absorptive medium for SVOCs (semi-volatile organic compounds). This process contributes about 27 % of the total organic mass. The model results are very similar to the LEAK chamber results. Overall, the sensitivity studies demonstrate that the particle reactivity and the particle-phase bulk diffusion require a better characterization in order to improve the current model implementations and to validate the assumptions made from the chamber simulations. The successful implementation and testing of the current kinetic gas-particle partitioning approach in a box model framework will allow further applications in a 3-D model for regional-scale process investigations.

Prediction of aqueous diffusion coefficients for organic compounds at 25°C

Chemosphere ◽  
1999 ◽  
Vol 38 (10) ◽  
pp. 2381-2406 ◽  
Author(s):  
Janet A. Schramke ◽  
Sheila F. Murphy ◽  
William J. Doucette ◽  
Wendell D. Hintze
Keyword(s):  
Organic Compounds ◽  
Diffusion Coefficients

Using the Quantitative Structure-Property Relationship to Correlate the Infinite Dilution Activity Coefficients of Organic Compounds in 1-Ethyl-3-Methylimidazolium Diethylphosphate

2012 ◽  
Vol 554-556 ◽  
pp. 1971-1974
Author(s):  
Ming Lan Ge ◽  
Ru Song Zhao ◽  
Jie Ming Xiong ◽  
Yu Feng Yi ◽  
Fu Chen Ding
Keyword(s):  
Organic Compounds ◽  
Activity Coefficients ◽  
Infinite Dilution ◽  
Solute Molecule ◽  
Quantitative Structure ◽  
Structure Property ◽  
Quantitative Structure Property Relationship ◽  
Property Relationship ◽  
Formal Charge ◽  
Structure Property Relationship

On the basis of the quantitative structure-property relationship (QSPR) method and the quantum chemical descriptors including molecular van der Waals volume (Vmc), dipole moments (μ), the most negative formal charge in solute molecule (q-), and the most positive formal charge on a hydrogen atom in solute molecule (q+) of organic compounds, the values of activity coefficients at infinite dilution, , for 16 solutes in ionic liquid 1-ethyl-3-methylimidazolium diethylphosphate ([EMIM][DEP]) at 323.15 K were correlated with the descriptors. The result showed that the QSPR model had a good correlation and could successfully describe . The quantitative relationship between organic molecular structure and in [EMIM][DEP] was obtained and the correlation parameters were analyzed to understand the interactions that affect activity coefficients at infinite dilution.

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