Immiscible liquids separation by copper ferrite coated mesh membranes: central composite statistical design-based growth optimization

Oil/water separation is a critical environmental and industrial challenge, as oil spills and oily wastewater discharge cause severe ecological damage and resource loss. Conventional separation methods often face limitations such as low efficiency, high operational cost, and poor reusability of separation media. In this study, a stainless steel mesh membrane with a copper oxide seed layer and a micro/nano‑structured copper ferrite coating was fabricated via a hydrothermal‑assisted growth process. The optimal synthesis parameters, determined using a central composite design (CCD), were a growth time of 11 h and 30 min, calcination temperature of 727 °C, and ammonia content of 0.54 mol. X‑ray diffraction (XRD) confirmed the formation of a cubic spinel CuFe₂O₄ phase with minor oxide impurities, while field‑emission scanning electron microscopy (FESEM) revealed a uniform nanorod morphology with enhanced surface roughness. Energy‑dispersive X‑ray spectroscopy (EDS) and elemental mapping showed a homogeneous distribution of Cu, Fe, and O with a Cu:Fe atomic ratio close to 1:2, and vibrating‑sample magnetometry (VSM) indicated ferromagnetic behavior. Surface energy analysis revealed a dominant polar component and negligible dispersive contribution, resulting in strong hydrophilicity and underwater oleophobicity. The optimized membrane achieved a water flux of 37,037 L m⁻² h⁻¹, a separation efficiency above 99.9 %, and an underwater oil contact angle of 146°±3.55° maintaining stable performance over ten reuse cycles. Mechanical abrasion and chemical exposure tests confirmed durability under acidic, alkaline, and saline conditions. Compared to previously reported membranes, the CCD‑optimized copper ferrite coating uniquely integrates mechanical resilience, chemical robustness, and long‑term reusability into a single high‑performance platform for efficient oil/water separation in demanding environments.