scholarly journals Improved AIOMFAC model parameterisation of the temperature dependence of activity coefficients for aqueous organic mixtures

2014 ◽  
Vol 14 (11) ◽  
pp. 16907-16995 ◽  
Author(s):  
G. Ganbavale ◽  
A. Zuend ◽  
C. Marcolli ◽  
T. Peter
Keyword(s):  
Temperature Dependence ◽  
Functional Groups ◽  
Activity Coefficients ◽  
Low Temperatures ◽  
Functional Group ◽  
Group Contribution ◽  
Organic Mixtures ◽  
Temperature Range ◽  
Organic Functional Groups ◽  
Organic Solutions

Abstract. This study presents a new, improved parameterisation of the temperature dependence of activity coefficients in the AIOMFAC (Aerosol Inorganic–Organic Mixtures Functional groups Activity Coefficients) model applicable for aqueous as well as water-free organic solutions. For electrolyte-free organic and organic–water mixtures the AIOMFAC model uses a group-contribution approach based on UNIFAC (UNIversal quasi-chemical Functional-group Activity Coefficients). This group-contribution approach explicitly accounts for interactions among organic functional groups and between organic functional groups and water. The previous AIOMFAC version uses a simple parameterisation of the temperature dependence of activity coefficients, aimed to be applicable in the temperature range from ~275 to ~400 K. With the goal to improve the description of a wide variety of organic compounds found in atmospheric aerosols, we extend the AIOMFAC parameterisation for the functional groups carboxyl, hydroxyl, ketone, aldehyde, ether, ester, alkyl, aromatic carbon-alcohol, and aromatic hydrocarbon to atmospherically relevant low temperatures with the introduction of a new temperature dependence parameterisation. The improved temperature dependence parameterisation is derived from classical thermodynamic theory by describing effects from changes in molar enthalpy and heat capacity of a multicomponent system. Thermodynamic equilibrium data of aqueous organic and water-free organic mixtures from the literature are carefully assessed and complemented with new measurements to establish a comprehensive database, covering a wide temperature range (~190 to ~440 K) for many of the functional group combinations considered. Different experimental data types and their processing for the estimation of AIOMFAC model parameters are discussed. The new AIOMFAC parameterisation for the temperature dependence of activity coefficients from low to high temperatures shows an overall improvement of 25% in comparison to the previous model version. The new parameterisation of AIOMFAC agrees well with a large number of experimental datasets and enables the calculation of activity coefficients of a wide variety of different aqueous/water-free organic solutions down to the low temperatures present in the upper troposphere.

scholarly journals Improved AIOMFAC model parameterisation of the temperature dependence of activity coefficients for aqueous organic mixtures

2015 ◽  
Vol 15 (1) ◽  
pp. 447-493 ◽  
Author(s):  
G. Ganbavale ◽  
A. Zuend ◽  
C. Marcolli ◽  
T. Peter
Keyword(s):  
Experimental Data ◽  
Temperature Dependence ◽  
Functional Groups ◽  
Organic Compounds ◽  
Activity Coefficients ◽  
Low Temperatures ◽  
Functional Group ◽  
Organic Mixtures ◽  
Organic Functional Groups ◽  
Organic Solutions

Abstract. This study presents a new, improved parameterisation of the temperature dependence of activity coefficients in the AIOMFAC (Aerosol Inorganic–Organic Mixtures Functional groups Activity Coefficients) model applicable for aqueous as well as water-free organic solutions. For electrolyte-free organic and organic–water mixtures the AIOMFAC model uses a group-contribution approach based on UNIFAC (UNIversal quasi-chemical Functional-group Activity Coefficients). This group-contribution approach explicitly accounts for interactions among organic functional groups and between organic functional groups and water. The previous AIOMFAC version uses a simple parameterisation of the temperature dependence of activity coefficients, aimed to be applicable in the temperature range from ~ 275 to ~ 400 K. With the goal to improve the description of a wide variety of organic compounds found in atmospheric aerosols, we extend the AIOMFAC parameterisation for the functional groups carboxyl, hydroxyl, ketone, aldehyde, ether, ester, alkyl, aromatic carbon-alcohol, and aromatic hydrocarbon to atmospherically relevant low temperatures. To this end we introduce a new parameterisation for the temperature dependence. The improved temperature dependence parameterisation is derived from classical thermodynamic theory by describing effects from changes in molar enthalpy and heat capacity of a multi-component system. Thermodynamic equilibrium data of aqueous organic and water-free organic mixtures from the literature are carefully assessed and complemented with new measurements to establish a comprehensive database, covering a wide temperature range (~ 190 to ~ 440 K) for many of the functional group combinations considered. Different experimental data types and their processing for the estimation of AIOMFAC model parameters are discussed. The new AIOMFAC parameterisation for the temperature dependence of activity coefficients from low to high temperatures shows an overall improvement of 28% in comparison to the previous model version, when both versions are compared to our database of experimentally determined activity coefficients and related thermodynamic data. When comparing the previous and new AIOMFAC model parameterisations to the subsets of experimental data with all temperatures below 274 K or all temperatures above 322 K (i.e. outside a 25 K margin of the reference temperature of 298 K), applying the new parameterisation leads to 37% improvement in each of the two temperature ranges considered. The new parameterisation of AIOMFAC agrees well with a large number of experimental data sets. Larger model–measurement discrepancies were found particularly for some of the systems containing multi-functional organic compounds. The affected systems were typically also poorly represented at room temperature and further improvements will be necessary to achieve better performance of AIOMFAC in these cases (assuming the experimental data are reliable). The performance of the AIOMFAC parameterisation is typically better for systems containing relatively small organic compounds and larger deviations may occur in mixtures where molecules of high structural complexity such as highly oxygenated compounds or molecules of high molecular mass (e.g. oligomers) prevail. Nevertheless, the new parameterisation enables the calculation of activity coefficients for a wide variety of different aqueous/water-free organic solutions down to the low temperatures present in the upper troposphere.

scholarly journals New and extended parameterization of the thermodynamic model AIOMFAC: calculation of activity coefficients for organic-inorganic mixtures containing carboxyl, hydroxyl, carbonyl, ether, ester, alkenyl, alkyl, and aromatic functional groups

2011 ◽  
Vol 11 (17) ◽  
pp. 9155-9206 ◽  
Author(s):  
A. Zuend ◽  
C. Marcolli ◽  
A. M. Booth ◽  
D. M. Lienhard ◽  
V. Soonsin ◽  
...  
Keyword(s):  
Liquid Phase ◽  
Functional Groups ◽  
Organic Compounds ◽  
Activity Coefficients ◽  
Atmospheric Aerosols ◽  
Atmospheric Chemistry ◽  
Inorganic Ions ◽  
Aqueous Mixtures ◽  
Organic Functional Groups ◽  
Ether Ester

Abstract. We present a new and considerably extended parameterization of the thermodynamic activity coefficient model AIOMFAC (Aerosol Inorganic-Organic Mixtures Functional groups Activity Coefficients) at room temperature. AIOMFAC combines a Pitzer-like electrolyte solution model with a UNIFAC-based group-contribution approach and explicitly accounts for interactions between organic functional groups and inorganic ions. Such interactions constitute the salt-effect, may cause liquid-liquid phase separation, and affect the gas-particle partitioning of aerosols. The previous AIOMFAC version was parameterized for alkyl and hydroxyl functional groups of alcohols and polyols. With the goal to describe a wide variety of organic compounds found in atmospheric aerosols, we extend here the parameterization of AIOMFAC to include the functional groups carboxyl, hydroxyl, ketone, aldehyde, ether, ester, alkenyl, alkyl, aromatic carbon-alcohol, and aromatic hydrocarbon. Thermodynamic equilibrium data of organic-inorganic systems from the literature are critically assessed and complemented with new measurements to establish a comprehensive database. The database is used to determine simultaneously the AIOMFAC parameters describing interactions of organic functional groups with the ions H+, Li+, Na+, K+, NH4+, Mg2+, Ca2+, Cl−, Br−, NO3−, HSO4−, and SO42−. Detailed descriptions of different types of thermodynamic data, such as vapor-liquid, solid-liquid, and liquid-liquid equilibria, and their use for the model parameterization are provided. Issues regarding deficiencies of the database, types and uncertainties of experimental data, and limitations of the model, are discussed. The challenging parameter optimization problem is solved with a novel combination of powerful global minimization algorithms. A number of exemplary calculations for systems containing atmospherically relevant aerosol components are shown. Amongst others, we discuss aqueous mixtures of ammonium sulfate with dicarboxylic acids and with levoglucosan. Overall, the new parameterization of AIOMFAC agrees well with a large number of experimental datasets. However, due to various reasons, for certain mixtures important deviations can occur. The new parameterization makes AIOMFAC a versatile thermodynamic tool. It enables the calculation of activity coefficients of thousands of different organic compounds in organic-inorganic mixtures of numerous components. Models based on AIOMFAC can be used to compute deliquescence relative humidities, liquid-liquid phase separations, and gas-particle partitioning of multicomponent mixtures of relevance for atmospheric chemistry or in other scientific fields.

scholarly journals New and extended parameterization of the thermodynamic model AIOMFAC: calculation of activity coefficients for organic-inorganic mixtures containing carboxyl, hydroxyl, carbonyl, ether, ester, alkenyl, alkyl, and aromatic functional groups

2011 ◽  
Vol 11 (5) ◽  
pp. 15297-15416 ◽  
Author(s):  
A. Zuend ◽  
C. Marcolli ◽  
A. M. Booth ◽  
D. M. Lienhard ◽  
V. Soonsin ◽  
...  
Keyword(s):  
Liquid Phase ◽  
Functional Groups ◽  
Organic Compounds ◽  
Activity Coefficients ◽  
Atmospheric Aerosols ◽  
Atmospheric Chemistry ◽  
Inorganic Ions ◽  
Aqueous Mixtures ◽  
Organic Functional Groups ◽  
Ether Ester

Abstract. We present a new and considerably extended parameterization of the thermodynamic activity coefficient model AIOMFAC (Aerosol Inorganic-Organic Mixtures Functional groups Activity Coefficients) at room temperature. AIOMFAC combines a Pitzer-like electrolyte solution model with a UNIFAC-based group-contribution approach and explicitly accounts for interactions between organic functional groups and inorganic ions. Such interactions constitute the salt-effect, may cause liquid-liquid phase separation, and affect the gas-particle partitioning of aerosols. The previous AIOMFAC version was parameterized for alkyl and hydroxyl functional groups of alcohols and polyols. With the goal to describe a wide variety of organic compounds found in atmospheric aerosols, we extend here the parameterization of AIOMFAC to include the functional groups carboxyl, hydroxyl, ketone, aldehyde, ether, ester, alkenyl, alkyl, aromatic carbon-alcohol, and aromatic hydrocarbon. Thermodynamic equilibrium data of organic-inorganic systems from the literature are critically assessed and complemented with new measurements to establish a comprehensive database. The database is used to determine simultaneously the AIOMFAC parameters describing interactions of organic functional groups with the ions H+, Li+, Na+, K+, NH4+, Mg2+, Ca2+, Cl−, Br−, NO3−, HSO4−, and SO42−. Detailed descriptions of different types of thermodynamic data, such as vapor-liquid, solid-liquid, and liquid-liquid equilibria, and their use for the model parameterization are provided. Issues regarding deficiencies of the database, types and uncertainties of experimental data, and limitations of the model, are discussed. The challenging parameter optimization problem is solved with a novel combination of powerful global minimization algorithms. A number of exemplary calculations for systems containing atmospherically relevant aerosol components are shown. Amongst others, we discuss aqueous mixtures of ammonium sulfate with dicarboxylic acids and with levoglucosan. Overall, the new parameterization of AIOMFAC agrees well with a large number of experimental datasets. However, due to various reasons, for certain mixtures important deviations can occur. The new parameterization makes AIOMFAC a versatile thermodynamic tool. It enables the calculation of activity coefficients of thousands of different organic compounds in organic-inorganic mixtures of numerous components. Models based on AIOMFAC can be used to compute deliquescence relative humidities, liquid-liquid phase separations, and gas-particle partitioning of multicomponent mixtures of relevance for atmospheric chemistry or in other scientific fields.

scholarly journals The Effects of Fire on Organic Functional Groups of Peat in Relation to Water Content

2015 ◽  
Vol 19 (3) ◽  
pp. 143
Author(s):  
Said Ramadhan ◽  
Fadly Hairannoor Yusran ◽  
Abdul Haris ◽  
Suhaili Asmawi
Keyword(s):  
Moisture Content ◽  
Water Content ◽  
Functional Groups ◽  
Functional Group ◽  
Water Levels ◽  
Time Interval ◽  
Total Acidity ◽  
Organic Functional Group ◽  
Organic Functional Groups ◽  
The Relationship

The aim of this research was to study the decline of organic functional group through the process of burning in peat. In addition, this study was also to examine the relationship between water content in peat and organic functional group after combustion (burning).  Peat drying was conducted in an oven at a temperature of 75°C with the interval of 0, 1, 2, 3, 4, 5 and 6 hours.  Each time interval had three replicates within two sets of experiments so that the total number of samples were 42 (experimental units).  Variables measured were moisture content, total acidity, COOH groups, and OH-phenolate.  The relationship between the water content with total acidity, COOH groups and OH-phenolate were determined by the equation y = bx + a.  The results showed that the relationship between the water content with organic functional group was linear.  While the relationship between peat water content with organic functional group after burning was irregular, although water levels through the process of burning have been greatly reduced. Keywords: Burning peat; organic functional groups; water content [How to Cite: Said R, FH Yusran, A Haris and S Asmawi. 2014. The Effects of Fire on Organic Functional Groups of Peat in Relation to Water Content. J Trop Soils 19: 143-149. Doi: 10.5400/jts.2014.19.3.143]    

scholarly journals Biogenic oxidized organic functional groups in aerosol particles from a mountain forest site and their similarities to laboratory chamber products

2010 ◽  
Vol 10 (2) ◽  
pp. 4789-4822 ◽  
Author(s):  
R. E. Schwartz ◽  
L. M. Russell ◽  
S. J. Sjosted ◽  
A. Vlasenko ◽  
J. G. Slowik ◽  
...  
Keyword(s):  
Carboxylic Acid ◽  
Functional Groups ◽  
Functional Group ◽  
Group Composition ◽  
Organic Aerosol ◽  
Anthropogenic Sources ◽  
Forest Site ◽  
Aerosol Composition ◽  
X Ray ◽  
Organic Functional Groups

Abstract. Submicron particles collected at Whistler, British Columbia, at 1020 masl during May and June 2008 on Teflon filters were analyzed by Fourier transform infrared (FTIR) and X-ray fluorescence (XRF) techniques for organic functional groups (OFG) and elemental composition. Organic mass (OM) ranged from less than 0.5 to 3.1μg m−3, with a project mean and standard deviation of 1.3±1.0 μg m−3 and 0.21±0.16 μg m−3 for OM and sulfate, respectively. On average, organic hydroxyl, alkane, and carboxylic acid groups represented 34%, 33%, and 23% of OM, respectively. Ketone, amine and organosulfate groups constituted 6%, 5%, and <1% of the average organic aerosol composition, respectively. Measurements of volatile organic compounds (VOC), including isoprene and monoterpenes from biogenic VOC (BVOC) emissions and their oxidation products (methyl-vinylketone/methacrolein, MVK/MACR), were made using co-located proton transfer reaction mass spectrometry (PTR-MS). We present chemically-specific evidence of OFG associated with BVOC emissions. Positive matrix factorization (PMF) analysis attributed 65% of the campaign OM to biogenic sources, based on the correlations of one factor to monoterpenes and MVK/MACR. The remaining fraction was attributed to anthropogenic sources based on a correlation to sulfate. The functional group composition of the biogenic factor (consisting of 32% alkane, 25% carboxylic acid, 2% organic hydroxyl, 16% ketone, and 6% amine groups) was similar to that of secondary organic aerosol (SOA) reported from the oxidation of BVOCs in laboratory chamber studies, providing evidence that the magnitude and chemical composition of biogenic SOA simulated in the laboratory is similar to that found in actual atmospheric conditions. The biogenic factor OM is also correlated to dust elements, indicating that dust may act as a non-acidic SOA sink. This role is supported by the organic functional group composition and morphology of single particles, which were analyzed by scanning transmission X-ray microscopy near edge X-ray absorption fine structure (STXM-NEXAFS).

Dislocation Tunneling in Plastically Deformed Aluminum

1999 ◽  
Vol 562 ◽  
Author(s):  
Eunjoo Thompson ◽  
R. O. Pohl
Keyword(s):  
Internal Friction ◽  
Temperature Dependence ◽  
Sound Velocity ◽  
Strain Amplitude ◽  
Strong Evidence ◽  
Low Temperatures ◽  
Temperature Range

ABSTRACTWe have measured the amplitude dependent internal friction (ADIF) and sound velocity down to 0.065 K of a 99.9999% (6N) aluminum that was plastically deformed by 1%. The strain amplitude was varied from ε = 1 × 10−8 to ε = 6 × 10−7, a factor of 60. It is observed that with increasing strain amplitude, both the internal friction and the sound velocity become temperature independent over an increasingly wider temperature range. ADIF measurements show a flattening of the temperature dependence of the strain amplitude at low temperatures which is taken to be strong evidence for dislocation tunneling.

scholarly journals Biogenic oxidized organic functional groups in aerosol particles from a mountain forest site and their similarities to laboratory chamber products

2010 ◽  
Vol 10 (11) ◽  
pp. 5075-5088 ◽  
Author(s):  
R. E. Schwartz ◽  
L. M. Russell ◽  
S. J. Sjostedt ◽  
A. Vlasenko ◽  
J. G. Slowik ◽  
...  
Keyword(s):  
Carboxylic Acid ◽  
Functional Groups ◽  
Functional Group ◽  
Group Composition ◽  
Organic Aerosol ◽  
Anthropogenic Sources ◽  
Forest Site ◽  
Aerosol Composition ◽  
X Ray ◽  
Organic Functional Groups

Abstract. Submicron particles collected at Whistler, British Columbia, at 1020 m a.s.l. during May and June 2008 on Teflon filters were analyzed by Fourier transform infrared (FTIR) and X-ray fluorescence (XRF) techniques for organic functional groups (OFG) and elemental composition. Organic mass (OM) concentrations ranged from less than 0.5 to 3.1 μg m−3, with a project mean and standard deviation of 1.3±1.0 μg m−3 and 0.21±0.16 μg m−3 for OM and sulfate, respectively. On average, organic hydroxyl, alkane, and carboxylic acid groups represented 34%, 33%, and 23% of OM, respectively. Ketone, amine and organosulfate groups constituted 6%, 5%, and <1% of the average organic aerosol composition, respectively. Measurements of volatile organic compounds (VOC), including isoprene and monoterpenes from biogenic VOC (BVOC) emissions and their oxidation products (methyl-vinylketone / methacrolein, MVK/MACR), were made using co-located proton transfer reaction mass spectrometry (PTR-MS). We present chemically-specific evidence of OFG associated with BVOC emissions. Positive matrix factorization (PMF) analysis attributed 65% of the campaign OM to biogenic sources, based on the correlations of one factor to monoterpenes and MVK/MACR. The remaining fraction was attributed to anthropogenic sources based on a correlation to sulfate. The functional group composition of the biogenic factor (consisting of 32% alkane, 25% carboxylic acid, 21% organic hydroxyl, 16% ketone, and 6% amine groups) was similar to that of secondary organic aerosol (SOA) reported from the oxidation of BVOCs in laboratory chamber studies, providing evidence that the magnitude and chemical composition of biogenic SOA simulated in the laboratory is similar to that found in actual atmospheric conditions. The biogenic factor OM is also correlated to dust elements, indicating that dust may act as a non-acidic SOA sink. This role is supported by the organic functional group composition and morphology of single particles, which were analyzed by scanning transmission X-ray microscopy near edge X-ray absorption fine structure (STXM-NEXAFS).

scholarly journals Experimental determination of the temperature dependence of water activities for a selection of aqueous organic solutions

2014 ◽  
Vol 14 (18) ◽  
pp. 9993-10012 ◽  
Author(s):  
G. Ganbavale ◽  
C. Marcolli ◽  
U. K. Krieger ◽  
A. Zuend ◽  
G. Stratmann ◽  
...  
Keyword(s):  
Temperature Dependence ◽  
Water Activity ◽  
Low Temperatures ◽  
Ice Nucleation ◽  
Dew Point ◽  
Strong Increase ◽  
Organic Systems ◽  
Activity Measurements ◽  
Organic Solutions ◽  
Selection Of

Abstract. This work presents experimental data of the temperature dependence of water activity in aqueous organic solutions relevant for tropospheric conditions (200–273 K). Water activity (aw) at low temperatures (T) is a crucial parameter for predicting homogeneous ice nucleation. We investigated temperature-dependent water activities, ice freezing and melting temperatures of solutions, and vapour pressures of a selection of atmospherically relevant aqueous organic systems. To measure aw over a wide composition range and with a focus on low temperatures, we use various aw measurement techniques and instruments: a dew point water activity meter, an electrodynamic balance (EDB), differential scanning calorimetry (DSC), and a setup to measure the total gas phase pressure at equilibrium over aqueous solutions. Water activity measurements were performed for aqueous multicomponent and multifunctional organic mixtures containing the functional groups typically found in atmospheric organic aerosols, such as hydroxyl, carboxyl, ketone, ether, ester, and aromatic groups. The aqueous organic systems studied at several fixed compositions over a considerable temperature range differ significantly in their temperature dependence. Aqueous organic systems of 1,4-butanediol and methoxyacetic acid show a moderate decrease in aw with decreasing temperature. The aqueous M5 system (a multicomponent system containing five different dicarboxylic acids) and aqueous 2-(2-ethoxyethoxy)ethanol solutions both show a strong increase of water activity with decreasing temperature at high solute concentrations for T < 270 K and T < 260 K, respectively. These measurements show that the temperature trend of aw can be reversed at low temperatures and that linear extrapolations of high-temperature data may lead to erroneous predictions. To avoid this, experimentally determined aw at low temperature are needed to improve thermodynamic models towards lower temperatures and for improved predictions of the ice nucleation ability of organic–water systems.

scholarly journals Competitor analysis of functional group H-bond donor and acceptor properties using the Cambridge Structural Database

2018 ◽  
Vol 20 (39) ◽  
pp. 25324-25334 ◽  
Author(s):  
James McKenzie ◽  
Christopher A. Hunter
Keyword(s):  
Crystal Structure ◽  
Functional Groups ◽  
Functional Group ◽  
Bond Formation ◽  
Cambridge Structural Database ◽  
Bond Properties ◽  
Donor And Acceptor ◽  
Competitor Analysis ◽  
Organic Functional Groups ◽  
Structural Database

The CSD can be used to obtain a reliable quantitative ranking of the H-bond properties of organic functional groups provided each crystal structure is individually analysed as the result of a competition between all of the functional groups present for H-bond formation.

X-ray diffractometry of AlGaAs/GaAs superlattices and GaAs in the temperature range 5–295 K

1989 ◽  
Vol 22 (4) ◽  
pp. 372-375 ◽  
Author(s):  
G. Clec'h ◽  
G. Calvarin ◽  
P. Auvray ◽  
M. Baudet
Keyword(s):  
Thermal Expansion ◽  
Temperature Dependence ◽  
Low Temperatures ◽  
X Ray ◽  
Lattice Constants ◽  
Temperature Range ◽  
Thermal Expansion Coefficients ◽  
Gaas Substrates ◽  
Expansion Coefficients ◽  
Tetrahedrally Bonded

The temperature dependence of the lattice constants of Al x Ga1 − x As/GaAs superlattices MBE-grown on (001) oriented GaAs substrates was determined by X-ray diffractometry. The thermal expansion coefficients of these materials become negative at low temperatures, like that of GaAs and other tetrahedrally bonded covalent solids. The temperature dependence of the stress in these structures was also studied; although its value increases as temperature decreases, strain remains elastic down to 5 K.

Sign in / Sign up

Export Citation Format

Share Document