Treatment of oil-based drilling cuttings by floatation-advanced oxidation two-step process

In this paper, a floatation-advanced oxidation two-step process was proposed for deep oil removal of oil-based drilling cuttings (OBDC). In the first stage, a novel and simple degreasing solution was prepared and most of the base oil contained by OBDC was removed by flotation; in the second stage, the oil content of OBDC was further reduced by combined ultrasound + ozone (US + O₃) advanced oxidation. The recommended degreasing solution was a mixture of methanol, ammonium chloride, and water with a mass ratio of 1.48.1 : 0.25. The best flotation process was as follows: a mass ratio of OBDC to degreasing solution of 1 : 10, stirring speed of 400 rpm and N₂ flotation with a flow rate of 400 mL min^-1 for 60 min. The oil content of OBDC can be reduced from 14.57% to 1.42% after flotation treatment and the degreasing solution can be reused more than five times. The optimal process of US + O₃ advanced oxidation was as follows: a mass ratio of OBDC to water of 1 : 10, ultrasonic power of 1000 W, and an ozone flow rate of 4.0 L min^-1 for 100 min. The oil content of OBDC can be reduced from 1.42% to 0.14% after US + O₃ treatment at room temperature. The results of this paper provide a new method and idea for OBDC treatment.