Diethanolamide derivatives as a potential enhanced oil recovery agent from indonesian castor oil and used frying oil: isolation, synthesis, and evaluation as nonionic biosurfactants

Mono-, di- and trihydroxy fatty acids were reacted in a free-solvent amidation reaction with diethanolamine to obtain the derivative of dialkanolamides.The ricinoleic acid and 9,10,12-trihydroxystearic acid were isolated and prepared from Indonesian castor oil, while 9,10-dihydroxystearic acid was synthesized from the used frying oil. Amidation reaction of methyl ricinoleate, 9,10-dihydroxystearic acid and 9,10,12-trihydroxystearic acid gave the dialkanolamide derivatives in 93.10, 49.66, and 38.78% yield, respectively. The chemical structure of the synthesized products was elucidated by FTIR and GC-MS through silylation method. The prepared compounds were evaluated for their physicochemical properties as nonionic biosurfactant such as Hydrophilic-Lyophilic Balance value, interfacial tension, critical micelle concentration, foam stability, emulsification index, and emulsion stability. It was found that more hydroxyl groups contribute to a higher Hydrophilic-Lyophilic Balance value, foam stability, emulsification index, and lower interfacial tension.