Modeling infinite dilution activity coefficients of organic-aqueous systems using a modified regular solution equation and cubic equations-of-state

Expressions derived from the regular solution equation and the generalized cubic equations-of-state (EOS) were employed to model the infinite dilute activity coefficient (gamma(infinity)) of organic-aqueous systems. A database of 119 organic species in aqueous systems, divided into six classes, was gathered for models evaluations. The use of the molar density, the first order molecular connectivity, and the dipole moment appear to be adequate correlating variables for describing the structural dependence of the residual part in the modified regular solution equation (MRS). The Soave-Redlich-Kwong (SRK) and Peng-Robinson (PR) were specified and employed in the generalized cubic EOS form. The excess activity coefficient concept was used in the SRK and PR EOS models to account for the deficiency of EOS in dealing with highly non-ideal or polar systems. The abilities of two existing correlation models along with two modified versions of the UNIFAC model were also assessed. The proposed models provide creditable equations for correlating gamma(infinity) of organic-aqueous systems.