A novel magnetically oscillatory fluidized bed using micron-sized magnetic particles for continuous capture of emulsified oil droplets

Treatment of emulsions is frequently required for water environment protection and oil recovery. Breaking the emulsion structure and separating the emulsified oil are key stages. However, conventional emulsion separation methods suffer from high reagent and energy costs, and low batch capacity. In this study, a novel magnetically oscillatory fluidized bed (MOFB) was developed to realize cost-effective and continuously operated emulsion separation through the introduction of reusable micron-sized magnetic particles (MMPs) and a low-energy electromagnetic field. The emulsified oil droplets were continuously captured by MMPs in oscillatory motion driven by a periodic electromagnetic field. The constructed MOFB showed excellent separation efficiency at a high influent flow rate of 20 mL/min. And in the long-term operation of the MOFB, a higher treatment capacity for emulsified oil was obtained by the MMPs (11.1 g liquid paraffin oil /g MMPs) than by the commonly used nano-sized magnetic particles. The entire oil capture process by moved MMPs was confirmed via in situ observation using a high-speed camera. To further reveal the oil capture mechanisms, meshing and kinematics analyses were performed to construct an indicator termed dynamic bed voidage (εD). It was found that the value of εD could be regulated by the magnetic field strength and frequency, and a low value of εD (<30.3%) was crucial to maintain a highly efficient capture of emulsified oil droplets. This study provides insights into the design of a novel magnetic separator for continuous emulsion separation and promotes technological evolution toward economically competitive separation methods.