Oil Extraction from Oil-Contaminated Drill Cuttings Using a Recyclable Single-Phase O/W Microemulsion

Abstract Oil-contaminated drill cuttings (OCDCs), often regarded as hazardous wastes, pose several environmental problems. Conventional methods exhibit certain drawbacks and limitations when used onsite. This paper developed a single-phase O/W microemulsion as a detergent and a practical processing method to treat OCDCs. The experimental results demonstrated that the oil retention could be reduced to a level that will allow offshore disposal. The used microemulsion and rinse water could be reused. The washed-out oil could be recycled to prepare oil based drilling fluid again when mixing with the same amount or greater of fresh base oil. Thus, the entire process of treatment was similar to microemulsion extraction. In the experiments, surfactant mixtures of sodium alcohol ether sulfate and n -butyl lactate were shown to form Winsor type I and type III microemulsions with N-pentyl propionate and linear Alpha Olefins C14 in the oil phase using a salinity scan. Two optimum formulas selected by the detergency performance were identified next to Winsor type III but still inside the Winsor type IV region, which is different from the lowest interfacial tension. By studying contact angle changes, one possible reason for this phenomenon was that for Winsor type III microemulsion, the higher concentration of surfactants cannot be washed away thoroughly with limited rinse water. The oil removal mechanism was also analyzed.