Study About Equation Of State For Nonaqueous Electrolyte Solution Systems

Theoretical and engineering models for the themodynamic properties of strong elestrolyte solutions have advanced significantly since 1985. This progress is notable in the ability to calculate selected properties of single and mixed strong electolyte solutions over a wide range of temperatures and compositions, including effects of various nonelectrolytes, solvents and supercritical components. Theoretical studies have begun to consider more realistic fundamental interactions between various components in these systems. There have been several successful models of theories based on the mean spherical approximation (MSA) and perturbation methods into engineering equations, without large numbers of empirical parameters. The capability to estimate a wide variety of thermodynamic properties accurately with a consistent set of equations and a small number of adjustable parameters has been achieved by several groups over limited temperature and composition ranges. Much work remains to be done, however, to understand completely the interplay and relative importance of various contributing energy effects.Equation of state (EOS) is used to represent the relationship between P-V-T of fluid, which has been developed very sccessfully from 19^th century. There are three different styles about EOS: cubic equation of state, multiconstants equation of state and theoretical equation of state. From beginning, researchers applied equation of state into the caculation about properties of pure fuild, and then used it to caculate the thermodynamic properties of mixing fluid by using mixing rules. EOS was proposed from gas phase originally, however, there are many EOS which can be uesd into liquid phase even solid-liquid mixture. This is favorable for caculation about different thermodynamic properties of fluid mixture with one model.A two parameters equation of state for nonaqueous electrolyte solutions system was developed. The EOS is in term of Helmholtz free energy and incorporated with results of low density expansion of non-primitive mean spherical approximation. The EOS was tested with experimental data reported in literatures of 9 nonaqueous single electrolyte solutions of which the temperature was 298.15K. The EOS in this work also has a good predictive capability for nonaqueous electrolyte solutions at different temperature. The comparasions with EOS published earlier by other researchers in literatures are carried out and the limitations of the model are also disscussed in detail.