Pickering emulsion based on chitosan with uniform droplet size for high-efficient and stable treatment of 4-nitrophenol wastewater

Abstract

Continuous flow catalytic system based on Pickering emulsion has extensive applications in wastewater treatment. However, the traditional method hardly prepares Pickering emulsion with uniform droplet and good stability, and the catalyst is loaded onto emulsifier difficultly. Herein, oil-in-water Pickering emulsion based on chitosan with excellent stability and uniform droplet is successfully prepared by a microfluidic chip to apply in an upflow bubbling fluidized bed reactor for the treatment of 4-NP wastewater. The catalyst can be stablely and efficiently loaded on chitosan emulsifier. And the uniform size distribution of Pickering emulsion droplet minimizes the flocculation and coalescence, guaranteeing adequate contact between the reaction solution and the catalyst. After the standing of 14 days, the diameter deviation of emulsion droplet prepared by microfluidic control method only is about 8.4 %. Remarkably, the reaction efficiency of high-concentration 4-NP wastewater for the fluidized bed reactor at 100 μL·min⁻¹ consistently remains above 99 % for 360 h.