Polymer brush-grafted cotton with petal-like microstructure as superhydrophobic and self-cleaning adsorbents for oil/water separation

Cotton serves as a popular base for modified materials, owing to its natural degradation properties, strong absorption capacity, and good extensibility. Further, magnesium hydroxide (Mg(OH)₂) is non-toxic, harmless, non-corrosive, and widely used in various fields. In this study, a self-cleaning, superhydrophobic, and super-absorbent cotton fabric was produced. The surface of the material was patterned with micro- and nano-structures, which was inspired by the effect of rose petals in nature. Microsheets of Mg(OH)₂ was deposited in a rose-shaped morphology on the surface of the cotton thread, after which the surface was modified with cetyltrimethoxysilane. The micro and nano rose-shaped patterns on the surface of the cotton thread facilitated the structural hydrophobicity and intercepted air on the material surface, while the introduction of cetyltrimethoxysilane further endowed the surface with high hydrophobicity. Overall, these imparted hydrophobic properties allowed for a water droplet contact angle of ~165°. This modified cotton fabric exhibited excellent self-cleaning performance with an oil-water separation efficiency of 99.9%. Further, the oil absorption rate was ~100%, while the oil storage rate for different oils ranged from 115.86% to 558.62% with good oil storage capacity. The modified fabric was also capable of separating emulsified oils. The lamellar microstructure of the rose-shaped Mg(OH)₂ microstructures and the formation mechanism of this morphology was investigated using scanning electron microscopy, X-ray powder diffraction, X-ray photoelectron spectroscopy, energy dispersive spectroscopy mapping, transmission electron microscopy, and selected area electron diffraction.