Abstract
Superhydrophobic methylated silica with a core–shell structure was successfully fabricated by a sol-gel process. First, a pristine silica gel with an average particle size of ca. 110 nm was prepared, using tetraethylorthosilicate (TEOS) as a precursor, ethanol as a solvent, and NH4OH as a catalyst. Then, the superhydrophobic methylated silica sol was prepared by introducing methyltrimethoxysilane (MTMS), to graft the surface of the pristine silica gel with methyl groups. The structure and morphology of the methylated silica sol were characterized by Fourier transform infrared (FTIR) spectroscopy, field emission scanning electron microscopy (FE-SEM), and transmission electron microscope (TEM). The characterization results showed that methyl groups were successfully grafted onto the surface of the pristine silica, and the diameter of the methylated silica was increased by 5–10 nm. Various superhydrophobic surfaces on glass, polyethylene terephthalate (PET) fabric, cotton, open-cell polyurethane (PU) foam, and polypropylene (PP) filter cloth were successfully constructed by coating the above substrates with the methylated silica sol and reached with a maximum static water contact angle and slide angle of 161° and 3°, respectively. In particular, the superhydrophobic PP filter cloth exhibited promising application in oil–water separation. The separation efficiency of different oil–water mixtures was higher than 96% and could be repeated at least 15 times.
Highlights
Superhydrophobic surfaces with a water contact angle (CA) greater than 150◦ and a sliding angle smaller than 10◦ have attracted huge interest for both fundamental research and practical applications [1], such as anti-sticking, anti-contamination, self-cleaning, and oil–water separation [2,3,4,5,6,7,8].The two basic principles of constructing superhydrophobic surfaces are suitable surface roughness and surface energy, which can be typically tuned by surface treatment [9,10]
Pristine silica gel was prepared by a sol-gel method, using to the Stöber method [43]
Pristine silica gel was prepared by a sol-gel method, using tetraethylorthosilicate (TEOS) as the precursor, ethanol as the solvent, and NH4 OH as the catalyst
Summary
Superhydrophobic surfaces with a water contact angle (CA) greater than 150◦ and a sliding angle smaller than 10◦ have attracted huge interest for both fundamental research and practical applications [1], such as anti-sticking, anti-contamination, self-cleaning, and oil–water separation [2,3,4,5,6,7,8]. The two basic principles of constructing superhydrophobic surfaces are suitable surface roughness and surface energy, which can be typically tuned by surface treatment [9,10] Based on such principles, many methods have been developed to prepare artificial superhydrophobic surfaces, including vapor deposition [11,12], etching [13,14], layer-by-layer assembly [15], self-assembly [16,17], electrospinning [18,19], phase separation [20], and sol-gel method [21,22,23]. Oil–water separation is critical for the treatment of oily wastewater and oil-spill accidents Traditional techniques such as oil skimming, centrifuge, coalesce, settling, filtration, and flotation technology are helpful in separating immiscible oil–water mixtures, but these methods are usually energy-consuming and not efficient [38]. It is interesting that the treated soft and hard materials exhibit outstanding water resistance and oil–water separation
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