Isotherm-Based Thermodynamic Models for Solute Activities of Organic Acids with Consideration of Partial Dissociation

Abstract

Organic acids make up a significant fraction of the organic mass in atmospheric aerosol particles. The calculation of gas-liquid-solid equilibrium partitioning of the organic acid is therefore critical for accurate determination of atmospheric aerosol physicochemical properties and processes such as new particle formation and activation to cloud condensation nuclei. Previously, an adsorption isotherm-based statistical thermodynamic model was developed for capturing solute concentration-activity relationships for multicomponent aqueous solutions over the entire concentration range (Dutcher et al. J. Phys. Chem. C/A 2011, 2012, 2013), with model parameters for energies of adsorption successfully related to dipole-dipole electrostatic forces in solute-solvent and solvent-solvent interactions for both electrolytes and organics (Ohm et al. J. Phys. Chem. A 2015). However, careful attention is needed for weakly dissociating semivolatile organic acids. Dicarboxylic acids, such as malonic acid and glutaric acid are treated here as a mixture of nondissociated organic solute (HA) and dissociated solute (H(+) + A(-)). It was found that the apparent dissociation was greater than that predicted by known dissociation constants alone, emphasizing the effect of dissociation on osmotic and activity coefficient predictions. To avoid additional parametrization from the mixture approach, an expression was used to relate the Debye-Hückel hard-core collision diameter to the adjustable solute-solvent intermolecular distance. An improved reference state treatment for electrolyte-organic aqueous mixtures, such as that observed here with partial dissociation, has also been proposed. This work results in predictive correlations for estimation of organic acid and water activities for which there is little or no activity data.

Influence of organic compound functionality on aerosol hygroscopicity: dicarboxylic acids, alkyl-substituents, sugars and amino acids

“…data and bulk literature data (Ninni and Meirelles, 2001;Kuramochi et al, 1997a). Furthermore, in Fig.…”

“…The hygroscopicity of an aerosol can be defined as the capacity of an aerosol particle to absorb water, and it quantifies the equilibrium partitioning of water between the gas and condensed phases (Krieger et al, 2012). Aerosol hygroscopic growth directly impacts the radiative balance of the atmosphere, with the size and refractive index of aerosol particles influencing their light scattering and absorption cross sections (Ravishankara et al, 2015;Moise et al, 2015). Similarly, the hygroscopic response of aerosol impacts the transport of chemical components in the environment and atmospheric chemical composition through heterogeneous chemistry and cloud chemistry, with implications for air quality (Akimoto, 2003;Farmer et al, 2015;Hallquist et al, 2009).…”

Statistical Thermodynamic Model for Surface Tension of Organic and Inorganic Aqueous Mixtures

“…[24][25][26][27][28] Organic + organic + water. In Figure 4, model prediction curves and data are shown at various constant mole ratios.…”

“…[24][25][26][27][28] Using statistical mechanics, the model gave predictions of multicomponent solution properties, such as water activity, osmotic coefficient, and solute activity, as a function of solute molality. Next, the adsorption isotherm was applied to the surface of a single solute aqueous solution, 21 with the important distinction of solutes being the adsorbates, partitioning to the surface phase by displacing water molecules.…”

Statistical Mechanics of Multilayer Sorption: Surface Concentration Modeling and XPS Measurement

“…As Wolfgang Pauli stated, “God made the bulk; surfaces were invented by the devil.” Yet modern technology, science, and engineering continue to appreciate and exploit the importance of surfaces because feature size in microelectronics becomes smaller, nucleation of atmospheric aerosol particles influences climate, and the complexity of protein folding in cell bilayers governs numerous biological processes. Over the past decade, Dutcher, Clegg, Wexler, and coworkers have used the statistical mechanics of multilayer sorption to describe thermodynamics of the bulk − and the surface − in complex and highly concentrated mixtures and related the parameter values in these equations to physicochemical properties of the solvent and solute. In parallel, experimental methods for measuring the concentration of solutes at the surface of solutions continue to improve.…”