Synthesis and Interfacial Properties of Bio-Based Zwitterionic Surfactants Derived from Different Fatty Acids in Non-Edible Vegetable Oils

Waste cooking oils and non-edible vegetable oils are abundant and renewable resources for bio-based materials which have showed great potential applications in many industries. In this study, five fatty acids commonly found in non-edible vegetable oils, including palmitic acid, stearic acid, linoleic acid, linolenic acid, ricinoleic acid, and their mixtures, were used to produce bio-based zwitterionic surfactants through a facile and high-yield chemical modification. These surfactants demonstrated excellent surface/interfacial properties with the minimum surface tensions ranging from 28.4 mN/m to 32.8 mN/m in aqueous solutions. The interfacial tensions between crude oil and surfactant solutions were remarkably reduced to lower values ranging from 0.0028 mN/m to 0.1983 mN/m without the aid of extra alkali, which particularly implied a great potential application in enhanced oil recovery. Meanwhile, these bio-based surfactants also showed good wetting properties (contact angles of ∼51° comparing with that of double distilled water, 92.04°) and appropriate predicted biodegradability (degradation order of "weeks" for bio-based surfactants synthesized from saturated fatty acids, and "months" for those synthesized from unsaturated fatty acids). Bio-based surfactants synthesized from unsaturated fatty acids showed better interfacial properties in reducing interfacial tension between crude oil and formation water. The bio-based surfactants presented in this study are alternative substitutes for traditional petroleum-based surfactants in various surfactant application fields.