Activity Coefficients at Infinite Dilution of Volatile Compounds in Water: Effect of Temperature and Salt Concentration

Abstract

Activity coefficients at infinite dilution in water have been determined for some aroma compounds detected in brown crab liquid effluent produced during boiling (1-octen-3-ol, 1-penten-3-ol, 3-methylbutanal, hexanal, benzaldehyde, 2,3-pentadione and ethyl acetate) by using the headspace gas chromatography technique (HSGC). Experimental data have been obtained over the temperature range of 40ºC to 50ºC. In this work, activity coefficients at infinite dilution for different type of systems have been considered: one component solute + water and multicomponent solute + water. No significant differences were observed between activity coefficients obtained in these two types of systems. Additionally the effect of salt concentration at 40ºC has been studied by varying salt concentration from 0 to 1.71 * Corresponding author. Tel.: +34 947 258810. Fax: ++34947258831. E-mail address tersanz@ubu.es 3 mol/kg. Experimental data were fitted as a function of salt concentration by using the Setschenow equation obtaining the salting out coefficient.

Concentration by pervaporation of brown crab volatile compounds from dilute model solutions: Evaluation of PDMS membrane

“…Table 5 lists the slopes of these plots together with the values previously reported in the study of the activity coefficients at infinite dilution. It can be observed that the values of the slopes obtained for the ln (J i, salty solutions /J i,non-saltysolution ) were lower than the values previously reported [7]. Therefore, blocking effect cannot be considered negligible.…”

“…In Eq. 9 with data of the activity coefficients obtained in previous work [7]. Table 5 lists the slopes of these plots together with the values previously reported in the study of the activity coefficients at infinite dilution.…”

“…Based on this result, it can be concluded that the "salting out" effect could dominate over the retarding effect on mass transport in the salt concentration range studied in this work. In a previous work [7], it was found that activity coefficients at infinite dilution increase with NaCl concentration. This higher activity coefficient can generate higher driving force and higher permeation flux (Eq.…”

“…Solution/diffusion model is used to describe the transport of permeating components through the membrane being proportional to the difference in partial vapor pressure at both sides of the membrane according to equation 1 [6]: In this work, the activity coefficients at infinite dilution in water were obtained from previous work in which activity coefficients at infinite dilution were obtained by using the headspace gas chromatography technique [7].…”

“…This parameter is recommended when comparing the separation performance of the membranes, since it allows distinguishing the effect of the nature of the membrane and the operating conditions. The permeances obtained in previous work with a POMS membrane [4] have been recalculated by using the new activitivy coefficients at infinite dilution recently published for the aroma compounds [7]. It can be observed from Table 2 that PERVAP TM 4060 membrane presents higher permeances for all the aroma compounds than POMS membrane, concluding better performance for PERVAP TM 4060.…”