Thermodynamic Study on Hydrotropic Aggregation Behavior of Benzamide

A comprehensive investigation on the solubility and mass transfer coefficient of benzamide through hydrotropy has been undertaken. This study was carried out using hydrotropes such as nicotinamide, sodium salicylate, resorcinol, and sodium citrate under the influence of a wide range of hydrotrope concentrations [(0 to 3.0) mol·L−1] and different system temperatures [(303 to 333) K]. It has been observed that the solubility of benzamide increases with an increase in hydrotrope concentration and also with system temperature. A Minimum Hydrotrope Concentration (MHC) in the aqueous phase was required to initiate significant solubilization of benzamide. Consequent to the increase in the solubilization of benzamide, the mass transfer coefficient was also found to increase with increase in hydrotrope concentration at 303 K. A threshold value similar to MHC is to be maintained to have an appreciable enhancement in mass transfer coefficient. The maximum enhancement factor, which is the ratio of the value in the presence and absence of a hydrotrope, has been determined for all sets of experimentations. To ascertain the hydrotropic aggregation behavior of benzamide, thermodynamic parameters such as Gibb’s free energy, enthalpy, and entropy of benzamide were determined. The Gibb’s free energy decreases with an increase in system temperature. The aggregation of hydrotropes was found to be exothermic in nature and favored by a positive value of entropy.