Durable and fluorine-free superhydrophobic coatings from palygorskite-rich spent bleaching earth

摘要

With the increasing consumption of vegetable oils, value-added recycling of spent bleaching earth (SBE) is of wide concern. Here, we report a simple and sustainable method for converting SBE containing palygorskite (PAL) to hybrid carbon materials (PAL/C) with a nanorod-like structure, which can then be used as building blocks for the preparation of durable and fluorine-free superhydrophobic coatings. The PAL/C composites were prepared by calcination of the SBE containing PAL in air. Then, the homogeneous suspensions in ethanol were prepared by hydrolytic condensation of n-hexadecyltrimethoxysilane onto the PAL/C nanorods. Superhydrophobic coatings can be readily prepared by spray-coating the suspensions onto substrates. The PAL/C composites and the superhydrophobic coatings were characterized using a variety of analytical techniques including scanning electron microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy. Superhydrophobicity of the coatings depends upon their surface topography, which can be precisely regulated by the calcination temperature of SBE and the concentration of the PAL/C composites in the suspensions. The superhydrophobic coatings show high water contact angle and extremely low sliding angle of 1.2 degrees. The superhydrophobic coatings also feature high mechanical, thermal and chemical durability. This is because the PAL/C nanorods are closely linked and encapsulated together by polysiloxane (POS) among them, forming a highly crosslinked network. We believe that this study will shed light on the value-added recycling of SBE and cost-effective preparation of bioinspired antiwetting coatings.