Photo-initiated polymer brush grafting and multi-stage assembly of hydrophobic oil-absorbing self-cleaning cotton fabrics for acidic and alkaline environments

Cotton fabrics brushed with a low surface energy polymer were prepared via a simple method, namely photo-initiated long-chain alkyl ester grafting. Silica was grafted to the fabric surface to increase the surface roughness, and the surface was further modified with cetyltrimethoxysilane (HDTMS), n-octyltrimethoxysiloxane (OTES), stearic acid (SA), or perfluoromethylenetrimethoxysilane (PF) to produce four superhydrophobic modified cotton fabrics (P-Brush@SiO₂@HDTMS, P-Brush@SiO₂@OTES, P-Brush@SiO₂@SA, and P-Brush@SiO₂@PF). All the four modified cottons all showed excellent hydrophobicity and the water droplet contact angles were 160°, 159°, 161°, and 171°, respectively. Furthermore, the modified materials were acid and alkali resistant, as well as recyclable. The fabrics were used to separate oil-water mixtures in extreme environments, where a separation efficiency of up to 98% (repeated oil absorption of more than 70 times) was achieved for pentane, hexane, heptane and octane. The absorption rate of the P-Brush@SiO₂@HDTMS, P-Brush@SiO₂@OTES, and P-Brush@SiO₂@SA cottons for dodecane is 99.9%, but the absorption rate of P-Brush@SiO₂@PF cotton for dodecane, tridecane and cetane is 0%, and the contact angle of oil droplets is 136° for tridecane. The four modified cotton fabrics show promise for wastewater treatment, specifically the separation of oil-water mixtures in extremely acidic or alkaline environments.