Immersion-Time-Controlled Growth of Cu(OH)₂ Microneedle Arrays on Copper Mesh for Superhydrophobic Oil-Water Separation

Abstract

Industrial wastewater, particularly from oil refining, presents serious environmental challenges. It contains oil, grease, and other contaminants that can disrupt water quality and threaten aquatic ecosystems. This research explores the fabrication of a Cu(OH)₂-coated copper mesh for oil-water separation by tailoring surface morphology and wettability. Cu(OH)₂ needle-like arrays were synthesized on Cu mesh via a facile chemical immersion process. The resulting high-aspect-ratio microstructures significantly altered surface roughness, thereby enhancing hydrophobicity and oleophilicity. A water contact angle of 155.75° and an oil contact angle of 17.52° were achieved for the optimised sample. As a result, oil-water separation efficiencies of 92.77%, 96.20%, 94.46%, and 98.10% were obtained for engine oil, diesel, olive oil, and cyclohexane, respectively. The highest permeation flux of 1648.65 kg·h⁻¹·m⁻² was observed for cyclohexane, attributed to its low viscosity. The results demonstrate that morphology-controlled Cu(OH)₂ microstructures can provide an effective and scalable route for oil-water separation without additional surface chemical modification.