Modification of the van Laar activity coefficient model

Based on statistical and mechanical arguments, the original van Laar activity coefficient model has been improved by reasonable assumptions. This modification has been done by replacing the van der Waals equation of state with the Redlich-Kwong equation of state in the formulation of van Laar with consistent mixing rules for the energy and volume parameters of this equation of state (a(mix), b(mix)). Other equations of state, such as the Soave modification of the Redlich-Kwong equation of state, Peng-Robinson and Mohsen-Nia, Modarress and Mansoori equations of state, have been introduced in the formulation of van Laar for the activity coefficients of the components present in the binary liquid mixtures, and their effects on the accuracy of the resultant activity coefficient models have been examined. The results of these revised models have been compared with the experimental data and it was found that the Redlich-Kwong equation of state with the van der Waals mixing rules for the volume and energy parameters of this equation, is the best choice among these equations of state. In addition, it can improve the original van Laar activity coefficient model and, therefore a better agreement with the experimental data is obtained.