Surface tension of binary mixtures of benzene + propionic acid and butanoic acid between 298.15 K and 318.15 K: Measurement and modeling

Experimental measurement of the surface tension of benzene + propanoic acid and benzene + butanoic acid has been carried out in the temperature range of 298.15 K to 318.15 K and atmospheric pressure. 170 new experimental points of surface tension have been obtained. Three theoretical models, i.e., Linear gradient theory (LGT), Shereshefsky model (SM), and the extended Langmuir model (LM), were used to modeling the surface tension and adsorption phenomenon of these binary mixtures. The three models correlated the surface tension of the benzene + carboxylic acid mixtures, and the average percent deviation was, 0.04% for LGT, 0.08% for SM, and 0.05% for LM. The Helmholtz density term and the liquid and vapor densities required in computing density with LGT were obtained with perturbed chain-statistical associating fluid theory equation of state (PC-SAFT EOS). Based on SM, the standard Gibbs energy of adsorption and the free energy change in the surface region were calculated. The free energy change was used to obtain the excess number of molecular layers in the surface region. The required parameters of the LM were adjusted, the standard Gibbs energy of adsorption was calculated, and negative deviations from ideality were determined. Also mole fractions of solute 0at surface were calculated by using LM. Additionally, by using surface tensions at different temperatures, specific surface enthalpy and specific surface entropy were calculated for (benzene + carboxylic acid) mixtures.