γ-Cyclodextrin-based metal-organic frameworks for lactonic sophorolipid application in enhanced oil recovery

Lactonic sophorolipid (LSL) exhibits numerous surfactant activities, such as emulsification, wetting action, dispersion effect, and oil-washing activities. Nevertheless, LSLs have poor water solubility, which restrains their application in the petroleum industry. In this research, a new compound, lactonic sophorolipid cyclodextrin metal-organic framework (LSL-CD-MOFs), was obtained by loading LSL into γ-cyclodextrin metal-organic frameworks (γ-CD-MOFs). The LSL-CD-MOFs were characterized by N₂ adsorption analysis, X-ray powder diffraction analysis, Fourier transform infrared spectroscopy, and thermogravimetric analysis. Loading LSL into γ-CD-MOFs significantly increased the apparent water solubility of LSL. However, the critical micelle concentration of LSL-CD-MOFs was similar to that of LSL. Furthermore, LSL-CD-MOFs effectively reduced the viscosities and improved the emulsification indices of oil-water mixtures. Oil-washing tests, which were conducted using oil sands, revealed that the LSL-CD-MOFs yielded an oil-washing efficiency of 85.82 % ± 2.04 %. Overall, γ-CD-MOFs are promising carriers for LSL, and LSL-CD-MOFs are a potential, low-cost, new, green surfactant for enhanced oil recovery.