USE OF IN SITU GENERATED SURFACTANT FOR CLEANING OF OIL-CONTAMINANT SOIL

摘要

Previously we have developed a novel extraction of bitumen from Athabasca tar sand using aqueous sodium silicate and ultrasound at ambient atmosphere and room temperature. Not only is a high accumulative recovery observed, but also the recovered bitumen is upgraded which is virtually free of asphaltene. The mechanism of the recovery and upgrading of bitumen reveals that the in situ surfactants are active in the system including the spent aqueous solutions after the organics have been separated. Gas Chromatography for Fourtier transformed infrared spectroscopy have revealed that the active compounds are the salts of long-chain carbox-ylic acids with carbon number 14-22, occasionally containing nitrogen and sulphur atoms. They are typical surfactants generated in situ. Those spent solutions, containing the active surfactants, can be used repeatedly for the separation of oil from sand during sonic treatment. Soil in many urban settings has been severely contaminated by petroleum hydrocarbons, especially service station refineries, etc. Another source of contamination is on site of the oilfield operation in production, recovery and transportation. Yet, the most important type is accidental spills of the shoreline and beaches, such as Exxon-Valdez. We have used the sodium silicate-ultrasound technique for treatment of a variety of oil contaminated soils and the results are exceedingly good in each case. In practice, a drilling bit assembly equipped with multiple transducers and solution delivery system has been constructed. The ultrasound can be delivered within a few meters from the centre of the tip. For shallow soil operations the assemblage can be operated manually or by self-propulsion along fixed rails. Sodium silicate solutions with a small amount of hydrogen peroxide is delivered from the annulus of the drilling equipment. Spent solutions with the emulsions are pumped to a holding tank for the waste oil to separate. The spent solution can be reused over continuously. The efficiency of the oil recovery from contaminated soil of Brown field (gasoline station and oil storage area) average 92% as compared to the chemical analysis. For oil pollution data, the Valdez oil spillbeach sands from Prince William Sounds, Alaska averages 95% and a silt clay lean sample from Santa Barabara Beach rich in humus material, the efficiency is only 52%. Evidently in the latter case the adsorption of oil into biomass material can be difficult for the ultrasound assisted caustic extraction.