Conversion of waste cooking oil to environmentally acceptable surfactants for enhanced oil recovery

Enhanced oil recovery (EOR) is a tertiary method used to extract crude oil remaining in reservoirs. With growing concerns about waste generation and its environmental impacts, waste cooking oil (WCO) has emerged as both a pollutant and a valuable renewable feedstock. WCO can be efficiently converted into sustainable surfactants with favorable surface and interfacial properties suitable for reservoir conditions. In this study, anionic and nonionic surfactants were synthesized from WCO: ethoxylated dodecylbenzene sulfonate (EABS14, aromatic) and ethoxylated hydrolyzed waste oil (EHWO14, aliphatic). Isopropanol was incorporated as a co-surfactant to enhance microemulsion performance. Phase behavior was evaluated at salinities of 50 × 10³, 100 × 10³, and 200 × 10³ ppm and at temperatures of 50 and 70 °C. Solubilization parameters and microemulsion phase volumes were used to determine optimal conditions. At optimum salinity, the dynamic interfacial tension (IFT) decreased significantly, reaching 1 × 10⁻³, 1 × 10⁻², and 8 × 10⁻² mN/m for EHWO14 + EABS14+CS, EHWO14, and EHWO14 + EABS14, respectively. Contact angles were reduced from 155° to 27°, 35°, and 22°, indicating effective wettability alteration. Flooding experiments confirmed the efficiency of WCO-derived surfactants, with maximum oil recovery at 100 × 10³ ppm and 50 °C. Recovery factors were 71.00% for EHWO14, 73.33% for EHWONa, 72.91% for EHWONa+EHWO14, and highest at 79.00% for the EHWO14 + EABS14+CS blend. These results demonstrate that WCO valorization into surfactants provides an eco-friendly and effective EOR alternative.