Determination of vapour–liquid and vapour–liquid–liquid equilibrium of the chloroform–water and trichloroethylene–water binary mixtures

The vapour–liquid equilibrium (VLE) and vapour–liquid–liquid equilibrium (VLLE) data are the basis for the design of distillation columns for the recovery or removal of residual extractant such as chloroform from wastewater. In this study, a new dynamic condensate-circulation still was designed and used for determination of VLE and VLLE of chloroform–water and trichloroethylene–water binary systems at 101.3 kPa. The phase diagrams of equilibrated vapour-phase composition versus overall liquid-phase composition y1–x1 (where subscript 1 references organic component in the binary system) and equilibrated temperature versus vapour-phase or overall liquid-phase composition T–x1(y1) were plotted by using the VLE and VLLE data and the data on mutual solubility. The experimental results showed that the two binary systems used have highly non-ideality and form heteroazeotropes, and their heteroazeotrope points are (t = 55.8 °C, x1 = y1 = 0.856) for chloroform–water and (t = 73.9 °C, x1 = y1 = 0.716) for trichloroethylene–water system. The activity coefficients of the component acted as solvent are in general, while the activity coefficients of the component acted as solute are very high in the equilibrated liquid phase. Correlation of the VLE and VLLE data respectively for the two binary systems with the NRTL (non-random two liquids) activity coefficient model gave satisfactory results.