Recyclable Janus hollow silica micron particles for efficient oil separation from oily wastewater

With the rapid development of industry, the environmental pollution caused by various oily wastewaters is becoming more and more serious. Therefore, it is urgent to exploit an environmentally friendly, highly efficient, and convenient method to scavenge the residual oil in crude oil/water emulsions. It is found that Janus particles have great potential in the treatment of oily wastewater due to their high interfacial activity. In this study, recyclable Janus hollow silica micron particles (J-HSMPs), were successfully synthesized by the improved Pickering emulsion method. Amphiphilicity of J-HSMPs was characterized and confirmed by using scanning electron microscopy, Fourier transform infrared spectroscopy, zeta-potential and contact angle measurements. The interfacial activity was further investigated by observing the dispersion behavior of J-HSMPs at oil-water interface and measuring the interfacial tension. The experimental results showed that J-HSMPs had excellent oil removal capability and reusability. Separation efficiency of crude oil and diesel oil could obtain 95.31 % and 96.17 %, respectively. After five cycles of application, the oil removal efficiency still could get >90 %. Amphiphilic J-HSMPs could cause tiny oil droplets in the water phase to aggregate into millimeter-sized oil droplets and carry them to the surface of water under influence of buoyancy, which helped to easily separate the water phase and oil droplets wrapped by J-HSMPs using a sieve. We anticipate that the as-prepared J-HSMPs will have promising and broad application prospects in cleaning oil spills, removing oil from domestic oily wastewater and crude oil emulsions in the process of petroleum industry.