Particle collision synergistic ultrasonic oxidation (PCUO) for oil-sludge treatment: Mechanisms of boundary film disruption and process optimization.

Oil-sludge treatment is hindered by stable multi-layer boundary films formed by heavy oil components. This study investigates the synergistic particle collision-ultrasonic oxidation (PCUO) method for disrupting these films. Single ultrasonic treatment achieves 49.85% total oil removal but fails to remove resins and asphaltenes (removal <20%), due to strong aromatic ring bonds at 1600 cm⁻¹ and hydroxyl hydrogen bonds at 3400 cm⁻¹ . In contrast, PCUO boosts their removal to 88.24% and 89.06% respectively, with total oil removal reaching 70.8%. Reducing sludge particle size D₅₀ from 216 μm to 18.91 μm decreases the ultrasound attenuation by 94.5% and increases sound intensity by 2%, correlating with a 34.09% improvement in oil removal efficiency, with optimal performance at D50 = 15-50 μm balancing ultrasonic penetration and re-adsorption risks. XDLVO confirms PCUO reduces oil-sludge interaction energy, enhancing treated sludge stability. Box-Behnken design optimization yields parameters: 10.15 min, 42.42 °C, pH 3.15, achieving 64.71% total oil removal with 82.0% heavy oil removal, significantly outperforming traditional technologies. In short, PCUO effectively disrupts complex boundary films, enhancing oil removal efficiency and providing a novel purification approach for oily solid waste.