From superhydrophilic to superhydrophobic polymer-nanoparticles coated meshes for water-oil separation systems with resistance to hard water

Abstract

A one-step procedure is presented for developing novel superhydrophobic oil-water separation membranes, based on composites of nanoparticles and polymers. The combination of hydrophilic particles with hydrophobic polymers allows obtaining superhydrophobic coatings on metal meshes, with chemical and physical stability. The methodology consists of coating SiO2 hydrophilic nanoparticles with two hydrophobic polymers (polydimethylsiloxane and polyvinylidene fluoride, PDMS and PVDF, respectively) on metal meshes. The nanoparticles generate roughness in the nanoscale, while the combination of PVDF and PDMS provides hydrophobicity, chemical resistance, and reinforce of mechanical properties. Membranes were characterized by XPS, SEM, TEM, FTIR, TGA, water-contact-angles (WCA) measurements, and elongation tests. The membranes present oil flux in the order of 102 Lm−2s−1, with stable performance during several months for water/oil separation tests when using saline (Na+, Cl−) and hard water (Ca+2, Mg+2) solutions. The synergetic mixture of three components, PDMS-PVDF-SiO2, provides superhydrophobic behaviour while coatings formed by any combination of only two components do not show the targeted properties.