A mesh membrane coated with dual-scale superhydrophobic nano zinc oxide: Efficient oil-water separation

A stainless steel mesh membrane decorated with mico/nano dual-scale structured ZnO have been fabricated via chemical bath deposition method. The fabricated surface shows excellent superhydrophobic/superoleophilic property in the air (water contact angle (WCA) of 160.1 degrees, oil contact angle (OCA) of 0 degrees) and superhydrophilic/superoleophobic behavior underwater (oil contact angle of 159.5 degrees and water contact angle of 0 degrees) with increasing annealing temperature up to 400 degrees C. Compared to previous different reports, low surface energy materials were not used in this work to regulate the surface wetting characteristics. Wetting characteristics of the mesh membrane surface were evaluated by the determination of morphological features and surface chemical composition. The FESSEM, XRD, Photoluminescence, and Raman analyses were used to characterize the prepared surfaces. The superhydrophobic mesh membrane was applied to separate chloroform-water mixtures. The reverse performance was examined by the superhydrophilic/underwater superoleophobic meshes, which were used to separate n-hexane-water mixtures. The prepared mesh membranes displayed high separation efficiency (> 99.9%) and high permeate flux for both light and heavy oil-water mixtures after at least ten separation cycles. This surface also shows excellent performance for the separation of highly corrosive aqueous solution and light/heavy oils mixtures with the separation efficiency of > 99.9%.