Constructing green, smart wettability-switchable and antibacterial Caragana cellulose filter by cooperative regulation of texture and surface for on-demand purification of emulsions

Abstract

The efficient on-demand purification of complex oily emulsions containing multiple pollutants and bacteria by a green filter has always been desired, but also extremely challenging. The abundant and renewable natural cellulose biomass is the best choice for developing green separation materials, but the limited separation capability of raw biomass restricts its application. To resolve this problem, this paper proposed a synergetic texture-surface regulation strategy to improve the liquid-locking ability and amphiphilicity of Caragana cellulose fiber, and thus prepared an intelligent multifunctional filter with an arbitrarily switchable underoil superhydrophobic (WCA = 152.1°) and underwater superoleophobic (OCA = 151.6°) surface. The surface wettability of the filter can be switched randomly by changing the wetting liquid, thus achieving efficient separation of different types of emulsions. As expected, both simulated different oils-in-water and different actual waters-in-oil emulsions, and all types of practical industrial oily complex emulsion sewage were purified by the filter at a high level (separation efficiency: 99.9 %). In addition, the filter can simultaneously remove 99.1 % of the Methylene blue and 98.6 % of the Oil red O in emulsions and has excellent antibacterial activity against E. coli (efficiency: 99.87 %) and S. aureus (efficiency: 99.43 %). The spent filter can be regenerated as an adsorbent capable of dynamically adsorbing 99.9 % of Orange II and 99.8 % of Methylene blue. This study provides a new method to modulate natural renewable cellulose and thus produce a multifunctional separation material for on-demand purification of complex and stubborn emulsions.