Oil/Water Interfacial Destabilization of Floated Oily Sludge Based on the Catalytic Decomposition of H₂O₂ Induced by Interfacial-Active Complexes

Abstract

Oil−inorganic material interactions at the oil/water interface have been extensively investigated as a fundamental research area. However, less focus has been placed on the oil/water interfacial process during the oily waste treatment process. In this study, the detailed oil/water interfacial destabilization process of a floated oily sludge (FOS) solution during Fenton-like treatment is investigated. A maximum of 66.1% of oil recovery was obtained from the FOS samples after the treatment. The influence of experimental conditions such as pH, hydrogen peroxide concentration, and reaction time on the oil percentage of sediments after treatment is also studied. The reduction of oil percentage in the FOS reached 77.5%, which indicated the high efficiency of the treatment. Rheological experiments showed that the bridge between the oil and coagulant mixtures in the FOS was destroyed after the addition of H 2 O 2 . Half of the H 2 O 2 (a total of 50 mM) was consumed, though nearly no free Fe 2+ could be detected in the FOS solution at a neutral pH. Electron paramagnetic resonance experiments demonstrated an enhanced generation of •OH that occurred due to the catalytic decomposition of H 2 O 2 by interfacial-active complexes (IAC). The interfacial destabilization process was triggered using a direct reaction of H 2 O 2 and iron-containing components in the IAC, as well as •OH induced oxidation of the sulfurcontaining components in the IAC at the oil/water interface. This research may provide a better understanding of oil−inorganic interactions at the oil/water interface during oily waste treatment and provide insight for the development of future processing strategies for oil recovery from oily sludge.