Fabrication of a robust superhydrophilic/underwater superoleophobic aluminum mesh for efficient oil–water separation

The treatment of oily wastewater demands separation materials that are efficient, durable, and resistant to harsh environments. In this work, a needle-like nanostructure (NLNS) was fabricated on a 200-mesh aluminum mesh (Base) through a two-step process combining plasma electrolytic oxidation (PEO) with hydrothermal treatment (HT). The effect of hydrothermal duration on the resulting morphology was systematically examined, identifying optimal conditions (200°C, 8 h) that yield a uniform, high-density NLNS. Unlike conventional PEO-based coatings, the sharp-tipped nanoneedle morphology maximizes capillary forces to stabilize a robust hydration layer, achieving exceptional underwater superoleophobicity with an underwater oil contact angle (UWOCA) as high as 168°. The NLNS exhibited high separation efficiency (up to 97.6%) for n-hexane/water mixtures under highly acidic, alkaline, and saline conditions, along with a stable permeation flux of ∼4900 L m −2 h −1 over 20 cycles. Durability assessments confirmed robust mechanical resistance (UWOCA > 140° after 16 friction cycles) and enhanced corrosion resistance. This strategy avoids toxic fluorinated modifiers and uses only water as the HT medium, providing a green, low-cost, and scalable route for industrial oily wastewater treatment. Download: Download high-res image (185KB) Download: Download full-size image