Optimization and mechanism of oily sludge treatment by ball milling method with combined surfactants

The complex properties of oily sludge have a significant impact on the ecological environment and present considerable treatment challenges. This study proposed a new method of ball milling with combined surfactants for oily sludge treatment. The optimal process parameters for treating oily sludge were determined by single-factor and orthogonal experiments. The results indicated that the residual oil rate was reduced from 14.70% to 1.83% with the oil removal rate of 87.55% at the rotate speed of 500 r/min, the mixture pH of 9, the cleaning time of 35 min, and the liquid‑to‑solid ratio of 5:1 mL/g. Additionally, the mechanism studies demonstrated that ball milling could reduce the particle size of oily sludge, which increased the contact area between sludge particles and cleaning agents. Meanwhile, ball milling could accelerate the desorption and release of petroleum hydrocarbons from the sludge matrix, thus significantly improving the cleaning efficiency of oily sludge. This work provided a new method for oily sludge treatment, which not only mitigated its environmental pollution but also held significant scientific value for future oily sludge management and the green, sustainable development of the petrochemical industry.