Preparation of superhydrophobic and superoleophilic cotton-based material for extremely high flux water-in-oil emulsion separation

Abstract

Highly stable emulsified water-in-oil mixtures from industrial processes have severe impact on the environment. As their abundance is increasing worldwide, the methods to effectively separate these emulsified water–oil mixtures have attracted significant interest in recent years. Herein, a durable superhydrophobic cotton-based material (SCM) using poly(vinyl phenol), 1,3-phenylene bisoxazoline, and raw cotton was developed. The as-prepared SCM possesses superhydrophobicity (water contact angle > 150°) and superoleophilicity (oil contact angle < 5°). The SCM has excellent repellence not only toward pure water, but also hot water and corrosive aqueous liquids. The superwetting composite also exhibits durable superhydrophobicity after long-term immersion in organic solvents. Moreover, after the compression process, the superwetting material exhibits a remarkable oil–water separation performance. Very high permeation flux values of up to 10,400 ± 400 L m−2h−1 and 867,500 ± 30,300 L m−2h−1 bar−1 are observed for the surfactant-stabilized water-in-oil emulsion by employing gravity-driven and external pressure filtration, respectively, with excellent efficiencies (oil purity of ≥ 99.97 wt%). The outstanding separation performance for various oils and organic solvents, stability in harsh chemical and physical environments, robustness, and recyclability of the superhydrophobic composite make SCM an excellent candidate for large scale application.