Upgrading waste polyethylene into superhydrophilic aerogel membrane for efficient oily emulsion wastewater treatment

Abstract

Removing oil from oily emulsion wastewater is critically required prior to their downstream processing. However, the commonly used superhydrophilic separation membranes suffer from a complex hydrophilic modification process, high cost, and low efficiency. Herein, a cost-effective superhydrophilic aerogel membrane was presented via phase transfer and low-temperature plasma strategy using waste polyethylene as a building block. This plasma strategy involves directly and swiftly introducing oxygen functional groups with high surface energy onto the membrane surface, avoiding classical and sophisticated wet chemistry such as graft polymerization or physical modification. Such a direct plasma strategy renders the intrinsically hydrophobic polyethylene-based aerogel membrane stable and robust superhydrophilicity in harsh environments and excellent underwater anti-oil adhesion properties, thus achieving excellent gravity-driven oil-in-water emulsions separation with high flux (1940 L m⁻² h⁻¹) and high separation efficiency (98.9%). Additionally, this directly hydrophilized aerogel membrane presents favorable reusability, thereby maintaining satisfactory separation flux and efficiency even after 10 cycles of separation. Overall, this work provides a general and efficient avenue to surface engineer polyethylene-based aerogel membrane for rapid separation of oil-in-water emulsion wastewater.