Modelling of solubility of mercaptans in water at low concentrations

Mercaptans is one of the major volatile organosulfur compounds produced in natural environments. The presence of mercaptans creates a great threat to the environmental safety and can cause health problems due to their toxicity, even at low concentrations. Knowledge on the thermodynamics properties and vapor-liquid equilibria of mercaptans-water is important for environmental impact studies and engineering design particularly when dilute aqueous systems are involved. In this work, we propose a generalized thermodynamic framework that uses Soave, Redlich and Kwong (SRK) EOS/Peng-Robinson (PR) EOS coupled with Huron-Vidal mixing rules to correlate the solubility of mercaptans-in water systems at low concentration. For this approach, the Huron-Vidal mixing rule are combined with infinite-dilution activity coefficients and the procedure is based on the reduced UNIQUAC model, suitable for infinite-pressure conditions. New binary interaction parameters are reported for studied systems for a wide range of pressure. By employing the pure component parameters with the values of infinite dilution activity coefficients, the solubility of mercaptans in water at dilute concentrations was predicted quite satisfactorily. The results of Root Mean Square Error (RMSE) illustrated good accuracy of the studied models for all systems considered in this work, with values of about 1.14-5.12%.