Interfacial Regulation of Natural Magnetite for Oil-Water Separation in Oily Petrochemical Wastewaters

The vast production of oily petrochemical wastewater poses significant economic and environmental challenges due to surfactants hindering natural oil-water separation, preventing dispersed oil recovery. Inspired by mineral flotation interfacial regulation principles, this study modified natural magnetite using oxide mineral collectors. This enhanced its interfacial activity, enabling assembly at the oil-water interface and rapid magnetic separation under an external field. FTIR, UV-Vis, and contact angle analyses confirmed successful magnetite surface modification. Oil adsorption tests demonstrated the modified magnetite's significantly increased oil affinity, while VSM verified the strong magnetic response of the formed magnetite-oil complexes. Under optimized conditions, oil-water separation efficiency reached 99.90% for laboratory-simulated wastewater and 90.67% for actual industrial petrochemical wastewater. An industrial-scale separation system based on this technology was designed and successfully implemented at a production site. Crucially, the process allows for the recovery and reuse of the separated dispersed oil through washing. This approach overcomes key limitations of existing industrial treatment methods, such as large equipment footprint, secondary pollution risks, and high chemical consumption. The modified magnetite-based magnetic separation offers a highly efficient and sustainable solution for treating challenging oily petrochemical wastewater while enabling resource recovery.