Saponin-rich extract from Glycyrrhiza glabra plant, a safe matter for low interfacial tension oil/water extraction

Interfacial tension (IFT) plays an important role in the processes like extraction and emulsification, and that low level IFT is usually preferred for better hydrodynamic performance of unit operations. The present study explores the effect of a saponin-rich extract from Glycyrrhiza glabra plant on the IFT of conventional n-hexane/water system. FTIR, HPLC and LC/MS analysis indicates a 31.39% glycyrrhizic acid as the main saponin, as well as flavonoid and phenolic compounds. The system IFT was decreased to 79.5% under the apparent CMC of about 0.20 wt%. Comparison of the obtained results with the previously reported results with extract products from other plants and with respect to much lower used dosage (less than 1:50) indicates the high preference of the product. More IFT reduction could still be achieved with temperature (within 293.2-313.2 K) and pH (within 5.5-8.5). Further, NaCl and CaCl2 salts caused more IFT reduction due to salting-out effect and in the order of Hofmeister series; however, by strengthening the salting-in effect, IFT raised in the presence of Na2SO4. The obtained data at different temperatures were nicely reproduced with a correlation based on Szyszkowski adsorption isotherm, and the corresponding parameters were obtained with reasonable variations. Consequently, the adsorption thermodynamic parameters were determined.