The feasibility of recovering oil from contaminated soil at petroleum oil spill site using a subcritical water extraction technology

The effective disposal of oily solid waste has received widespread attention due to its complex combination of various petroleum hydrocarbons, water, heavy metals and solid particles. Removal/recovering oil from such waste can be a feasible option. In this study, a subcritical water extraction (SWE) process was used to remove and recover oil from oil-contaminated soil. Under the experimental conditions (90 min extraction at 260 °C at the gauge pressure of 8 MPa and the water-to-soil ratio of 3:1), we achieved an oil removal efficiency of about 86% in the soil residue after extraction and we recovered approximately 39% of the oil. The possible presence of organic compounds in the recovered oil indicated by Fourier transform infrared spectroscopy (FTIR) spectra was consistent with the gas-chromatography and mass spectrometry (GC-MS) analysis, which was composed of various aromatic and aliphatic hydrocarbons. The physicochemical properties and heavy metal content of the recovered oil were also measured. The fuel characteristics of the recovered oil had similar fuel characteristics as commercial crude oil. These characteristics included density, specific gravity, element composition and heating value. The results showed that SWE treatment has the potential to remove and recover oil from oily contaminated soil.