CO2-switchable surfactant-free microemulsion consisted of N,N-dimethylcyclohexylamine, ethanol and water.

N,N-Dimethylcyclohexylamine—a switchable-hydrophilicity solvent, ethanol and water could be used to prepare a CO₂-switchable surfactant-free microemulsion (SFME). The ternary phase diagram was used to investigate the phase behavior of SFME. The electrical conductivity measurement, UV-visible spectra were used to investigate the microstructure and structural transition of SFME. Dynamic light scattering could be used to measure the diameter of SFME. The above results indicated that the microemulsion existed three microstructures: water-in-DMCHA (W/O), bicontinuous, and DMCHA-in-water (O/W). The variation tendency of electrical conductivity of SFME while CO₂ and N₂ alternately passing through was determinate, which proved SFME has excellent CO₂-switchable performance. Residual oil rate that using the W/O SFME to clean oily drill cuttings is very low, and oil from cuttings can be recycled, which shows CO₂-switchable SFME has much significance in washing oily drill cuttings. [ABSTRACT FROM AUTHOR]