Co-functionalization of cotton with hydrophobic nanoparticles and HDMTS as a durable, simple and fluorine-free approach for water-repellent, easy-cleaning and oil–water separation applications

• Combination of hydrophobic nanoparticles and HDMTS synergically imparted cotton with high water contact angle and low sliding angle. • Modified cotton presented a stable performance after being subjected to different harsh mechanical and chemical conditions. • Hydrophobic alumina combined with HDMTS was the one that presented better oil–water separation features. Cotton’s intrinsic hydrophilic nature poses a major limitation to its application in specialized fields such as oil/water separation. Although significant efforts have been made to impart the surface of different fabrics with superhydrophobic properties, most of the reported approaches rely on fluorinated-based compounds, which are harmful to the environment. In this study, high hydrophobicity was achieved through a combination of nanomaterials to create micro/nano roughness with Hexadecyltrimethoxysilane (HDMTS) to reduce the surface free energy. Results showed that impregnating cotton with nanomaterials followed by HDMTS treatment increased the water contact angle to values close to 150° and low sliding angles. This hydrophobicity was not compromised after repeated tape-peeling adhesion cycles, ultrasonication or immersion in solutions with different pH values and organic solvents. Their hydrophobic properties made them able to resist aqueous stains, and cotton’s inherent breathability was not compromised by the modification approach performed. The functionalized cotton also presented remarkable easy-cleaning and oil–water separation features, especially cotton modified with hydrophobic alumina nanoparticles, with a separation efficiency of 98.9% after 20 cycles. In summary, combining these nanomaterials with HDMTS has great potential to create highly hydrophobic and robust cotton. Furthermore, we can easily adapt this straightforward, environmentally conscious method for large-scale production.