Facile modification of nylon filter via vacuum coating with chitosan@MCM-41/GO for efficient oily wastewater treatment

Abstract

Contaminated water, containing oily waste, dyes, and pesticides, poses a major environmental threat. To address these challenges, herein, a stable superhydrophilic and underwater superoleophobic membrane (SHL/UWSOB) was designed by functionalizing a nylon filter (NF) with a homogeneous emulsion of chitosan-functionalized MCM-41 (CH@MCM-41) and graphene oxide (GO) via vacuum coating. Characterization results showed that the hydrophilic coating layer deposited efficiently on the NF substrate. The initial water contact angle (WCA) of the optimized 2-CH@MCM-41/GO-NF was 15°, which dropped to 0° within 3–4.5 seconds, and the underwater oil contact angle (UWOCA) was 161°. The resulting membrane exhibited an exceptional water permeation flux (2698 L m⁻² h⁻¹) and oil–water separation efficiency (99%) for different oil emulsions under 0.05 MPa. This improved performance was attributed to the hydrophilic CH@MCM-41, which was effectively embedded between GO sheets, creating micro–nanochannels. Additionally, the nylon filter modified with hydrophilic coating contained numerous OH, NH₂, COOH, and epoxy groups on its surface, enabling the removal of cationic dyes (methylene blue, malachite green and rhodamine B) and pesticides (nitenpyram and carbofuran) via adsorption. Various physical and chemical interactions between CH@MCM-41 and GO ensured higher coating stability on the NF substrate under high salt and acidic/alkaline conditions. The membranes' simple preparation method and improved multifunctional performance highlight the potential for developing hybrid membranes for environmental remediation.