Fabrication of durable superhydrophobic coatings on cotton fabrics with photocatalytic activity by fluorine-free chemical modification for dual-functional water purification

Superhydrophobic/superoleophilic fabrics have been the subject of profound research for self-cleaning and oil-water separation applications. However, the practical application of these materials is still limited due to the complex preparation process using fluorinated chemicals and poor stability of the developed coatings on the surface of fabrics under harsh environmental conditions. In this study, we fabricated a dual-functional coating on cotton fabric with superhydrophobicity and visible light photocatalytic activity via an inexpensive dip coating method. The in situ synthesized poly-triethoxyvinylsilane (PTEVS) with the combination of polydimethylsiloxane (PDMS) was used to obtain a superhydrophobic coating and subsequently a AgBr coating to integrate the photocatalytic activity. The surface morphology and chemical structure of the coated fabric were characterized by field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy and Fourier transform infrared spectroscopy. The coated cotton fabric exhibited self-cleaning, superhydrophobic and superoleophilic properties simultaneously with a water contact angle of similar to 154 degrees, a water sliding angle of similar to 8 degrees and an oil contact angle of similar to 0 degrees. The modified fabric can effectively separate a series of oil-water mixtures after being used repeatedly for 10 cycles through an ordinary filtering process. The coated fabric further purifies water containing soluble dyes under visible light illumination. Moreover, the durability of the coating was evaluated under harsh environmental conditions for example exposure to acidic, alkaline, salty solutions, ultraviolet irradiation, mechanical abrasion, and using the adhesive tape test, and the results of all these tests suggested that the coating was stable.