Using a switchable water to improve sustainable extraction for oil sands by low-concentration surfactant solution

Abstract

Surfactant extraction is the common method for treating oil sands. However, the recovery of traditional surfactant is difficult, and the oil emulsification phenomenon and generation of tailings are also caused easily. To develop the cleaner and sustainable approach for treating oil sands, a switchable water N, N, N′, N′-tetramethylhexanediamine (TMHDA) was used to improve extraction by surfactant sodium dodecyl benzene sulfonate (SDBS) solution with low concentration. Here, the TMHDA-containing SDBS solution has CO2 switchability because of the electrostatic interaction between SDBS solution and TMHDA with CO2 response, and can be also emulsify reversibly n-heptane, diesel oil, even crude oil, providing the possibility for separating oil from oil sands. The effective extraction of oil sands is performed by 1 mM (less than critical micelle concentration (CMC)) SDBS solution combined with TMHDA, which was also demonstrated by thermogravimetric analyzer, scanning electron microscope and elemental analysis. The residual oil content of oil sands is reduced to 0.515 wt% and 90.8% oil is removed by adding 0.15 g/mL TMHDA. Interestingly, oil is separated and fine sands is separated by introducing CO2, and the TMHDA-containing SDBS is recycled upon N2/65 °C.According to the detection of interfacial tension and Fourier Transform Infrared Spectroscopy (FTIR), it is demonstrated that the improved oil removal is ascribed to the adsorption of SDBS on solid surface and the reduced oil-water interface tension by the addition of TMHDA. Based on the evaluation of economic and environmental value, this sustainable approach exhibits potential application for treating oil sands in practical industry.