Simultaneous oil recovery and hydrocarbon degradation in aged oily sludge via jet cavitation

The efficient treatment of aged oily sludge, a challenging by-product of the petroleum industry, is crucial for resource recovery and environmental protection. Conventional methods often suffer from limited oil recovery efficiency. This study proposes a novel application of jet cavitation technology to disintegrate aged oily sludge, aiming to enhance oil recovery and reduce petroleum hydrocarbon content. The mechanism of disintegration involves both mechanical and chemical effects: the mechanical forces destroy hydrogen bonds to facilitate oil phase desorption, while cavitation-induced chemical bond rupture and free radical oxidation degrade long-chain hydrocarbons into short-chain compounds. The physicochemical properties (oil components, functional groups, petroleum hydrocarbons) of the sludge were comprehensively analyzed before and after treatment using multi-scale characterization techniques, including laser particle sizing, contact angle and Zeta potential measurements, combined with Thin Layer Chromatography-Flame Ionization Detection (TLC-FID), Fourier Transform Infrared Spectroscopy (FT-IR), and Gas Chromatography-Mass Spectrometry (GC-MS). Under optimized conditions (inlet pressure of 14.9 MPa, jet water temperature of 40°C, sludge concentration of 21.16%, hydraulic retention time of 5.98 s, and sludge temperature of 50°C), a maximum oil recovery rate of 84.95% was achieved. This result is significantly superior to the efficiency obtained via ultrasonic cavitation treatment, demonstrating the notable advantage and potential of the jet cavitation method for the effective treatment of aged oily sludge.