Limited robustness is a serious drawback for superhydrophobic coatings and degrades the performance of superhydrophobic surfaces in practical applications. Although fluororeagents have excellent durability for superhydrophobicity, their use has been restricted due to various health and environmental concerns. In this work, we describe a facile and efficient fabrication strategy for creating robust fluorine-free superhydrophobic composite coatings that are prepared by a simple dip-dry method, in which the H3BO3-incorporated SiO2–alkyl-silane coatings are deposited on woven cotton fabric surfaces followed by polydimethylsiloxane modification. The coated surface shows a large water contact angle of 157.95 ± 2° and a small sliding hysteresis angle (SHA) of 3.8 ± 0.6°, demonstrating excellent superhydrophobicity. The coated fabric surface also exhibited robustness and durability, withstanding a tape-peeling test (under 48.05 kPa) for around 80 repetitions and sandpaper rubbing (loaded 100 g) for 40 cycles. Furthermore, the coated fabric surface displayed self-healing and oil–water separation capacities. The developed superhydrophobic coatings in this study are robust, environmentally benign, and easy to fabricate, showing promising applications in textile industries.

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This study reports a novel cross-linking approach to fabricate the hydrothermally neutralized silica hydrogel of SiO2–H3BO3–hexadecyltrimethoxysilane by grafting alkylsilane groups onto the nanoporous silica. The synthesized silica hydrogel possessed a large specific surface area of 51.3 m2g–1 and showed excellent dye adsorption capability of cationic dyes in neutral (pH 7) and alkaline (pH 9) medium from wastewater. The colloidal electrokinetic potential analysis revealed that the outstanding adsorption efficiency of cationic dyes over anionic dyes strongly relies on the surface charge of the hydrogels. Moreover, the hydrophobic interactions between the dye molecules and the hydrogels were studied, and it was found that the dye adsorption performance can be tuned by altering the concentration of hydrophobic reagents of the hydrogel. The dye adsorption mechanism was established, and the kinetic study suggested that the adsorption is a pseudo-second-order reaction. Adsorption isotherms at various equilibrium conditions fitted well with the Langmuir isotherm. Therefore, this strongly supports the promising and practical application of the prepared silica hydrogel. The recyclability of the hydrogel was studied, and it showed 90% adsorption efficiency by the regenerated gel up to 6 cycles, which has a high potential in wastewater treatment.

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