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Basic Chemical Thermodynamics and Kinetics
Published in Kalliat T. Valsaraj, Elizabeth M. Melvin, Principles of Environmental Thermodynamics and Kinetics, 2018
Kalliat T. Valsaraj, Elizabeth M. Melvin
The UNIFAC method is especially suitable for activity coefficients of complex mixtures. It was developed for nonelectrolyte systems and should be used only for such systems. Most of the data for group contributions were procured at high mole fractions, and therefore extrapolation to very small mole fractions (infinitely dilute) for environmental engineering calculations should be made with circumspection. Arbuckle (1983) noted that when the mole fractions were very small, UNIFAC underpredicted the solubilities. Banerjee and Howard (1988) also noted this and have suggested useful empirical corrections. Despite these observations, it is generally recognized that for most complex mixtures UNIFAC can provide conservative estimates of activity coefficients. Its remarkable versatility is evident when mixtures are considered. As more and more data on functional group parameters in UNIFAC become available, this may eventually replace most other methods of estimation of activity coefficients.
Pervaporation separation of ethylacetate-ethanol mixtures using zeolite 13X-filled poly(dimethylsiloxane) membrane
Published in Chemical Engineering Communications, 2022
Sebnem Senol, Buket Kaya, Inci Salt, Berk Tirnakci, Yavuz Salt
UNIFAC method is a reliable and fast method to estimate activity coefficients under non-electrolyte, low and medium pressures, and temperatures in the range of 300-425 K (Gmehling et al. 1982; Letyanina et al. 2016). In the present study, binary interaction parameters were determined from liquid activity coefficients and excess Gibbs energies to describe the thermodynamic interactions in ternary systems. Interaction parameters between the polymer and solvent were calculated using data obtained from sorption experiments. Pristine PDMS and mixed matrix PDMS/13X membranes were prepared, and then swelling and single component pervaporation experiments were conducted at temperatures of 30, 40 and 50 °C for pure substances. The separation performance of the PDMS/13X membrane for EtOAc–EtOH mixture was investigated at a constant temperature of 30 °C. The composite membranes prepared were characterized by FT-IR, TGA, and SEM.
Uptake/release of organic contaminants by microplastics: A critical review of influencing factors, mechanistic modeling, and thermodynamic prediction methods
Published in Critical Reviews in Environmental Science and Technology, 2022
Domenica Mosca Angelucci, M. Concetta Tomei
Infinite dilution coefficients (and related Kpw) are evaluated by the UNIFAC (UNIQUAC Functional-group Activity Coefficients) group contribution approach (Scilipoti et al., 2014; Wang & Achenie, 2002). This thermodynamic method is based on molecular group interactions at equilibrium in an aqueous-solute-extractant system. The UNIFAC method, originally developed for solvent-solute interactions, has been integrated to include the consideration of polymers as extracting media via the UNIFAC-van der Waal-Free Volume (UNIFAC-vdW-FV) program (Kannan et al., 2005).