Study on Treatment of Oil-bearing Wastes

High temperature thermal decomposition and chemical extraction are commonly used in the innocent treatment of oilbearing wastes in operation areas. These treatments require the construction of a plant for the centralized processing of the wastes and gigantic equipment with high energy consumption is required. In collecting the wastes, environmental risks have to be considered. Nano emulsion at normal temperatures can rapidly separate oil from oil-bearing wastes, providing a good base for the "treatment while producing" of oil-bearing wastes. In laboratory study, a mixture of a surfactant, a secondary surfactant and water in different rations was further mixed with n-octane in a ratio between 1:9 and 5:5. The final mixture was agitated with supersonic wave at frequencies between 10-100 Hz to obtain a Winsor IV type single phase nano emulsion NR-A. The particle size, D90, of the NR-A emulsion measured on a laser particle size analyzer was 11 nm, and the interfacial tension between oil and water, as measured with the DuNouy method, was only 1.35 mN/m. The Zeta potential of the emulsion system was greater than 50 mV, indicating that the system was a thermodynamic dispersion. Adding the NR-A into oil-bearing wastes, the oil phase of the wastes can be desorbed from the solids under low energy consumption through fast mass transfer and ultra-low interfacial tension. Laboratory evaluation showed that when 0.5% NA-R was mixed with oil-bearing wastes from shale gas drilling, after agitation at room temperature for 20 min, 95.7% of the oil-on-waste was desorbed from the wastes. The desorbed oil can be used as the base oil for mixing oil base drilling fluids, realizing the efficient treatment and recycling of oil-bearing wastes.