The non-electrolyte NRTL-NRF model has been modified to study electrolyte solutions. The modified model for electrolytes is composed of short range part expressed by the modified nonelectrolyte NRTL-NRF and the Pitzer-Debye-Hückel equation to represent the long range interactions of ions in the solution. In this work, a salt specific parameter is used. Various types of experimental data including binary and ternary activity and osmotic coefficients, solid and gas solubilities in aqueous NaCl and also aqueous Methyldiethanolamine ( MDEA) data at wide temperature and pressure ranges have been implemented to check the performance of the present model. The overall relative standard deviation of 0.046 has been achieved for 130 strong aqueous binary electrolytes by the new model in fitting the experimental data of activity coefficients. The percent of absolute average deviations of the modified model for CO2+ MDEA+ H2O and H2S+ MDEA+ H2O are 30.3% and 24.8%, respectively. The results show good capabilities of the model for electrolyte solutions.

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