High-efficient Treatment of 4-Nitrophenol Wastewater in an Upflow Bubbling Fluidized Bed Reactor Based on Pickering Emulsion

The Pickering emulsion continuous flow catalytic system is widely applied in chemical synthesis and catalytic reaction. However, the traditional system generally adopts top feeding method resulting in the tight bed, which greatly limits the flow and transport of reactant. Herein, a upflow bubbling fluidized bed reactor based on Pickering emulsion is successfully constructed to the treatment of 4-nitrophenol wastewater. Here, the stable and efficient O/W Pickering emulsion in the bed reactor benefits from the preparation of an emulsifier with highly active interfacial catalyst (Pd@SiO2). The flow configuration from bottom to top and H2 bubbles from the hydrolysis of NaBH4 can produce the obvious looseness of bed with Pickering emulsion in the continuous flow system, improving the flow and transport of reactant to catalyst surface and the reaction performance. Under the condition of low catalyst loading (0.2 wt%), the conversion of high concentration 4-NP (1 mM) wastewater remains more than 98.5 % for 60 h constantly, demonstrating the excellent catalytic efficiency of the bubbling fluidized bed reactor. Results show that a continuous flow catalytic system with the new flow configuration yields outstanding performance for wastewater treatment.