One-step removal of insoluble oily compounds and water-miscible contaminants from water by underwater superoleophobic graphene oxide-coated cotton

We prepared a superhydrophilic/underwater superoleophobic graphene oxide (GO)-coated cotton for wastewater purification by a simple approach to overcome the difficulty of simultaneously removing insoluble oily compounds and water-miscible contaminants from water. GO can be attached onto the surface of cotton fibers by means of hydrogen bonds between oxygen-containing groups of GO and cotton, with a mass fraction of 6.9 wt%. Large numbers of oxygen-containing groups, combined with the inherent three-dimensional network structure, lead to a water contact angle of 0A degrees and an underwater oil contact angle of 170A degrees A +/- 1A degrees on the GO-coated cotton. Various oil-in-water emulsions, dye wastewaters and even mixtures of both can be economically and effectively purified by using GO-coated cotton. Most of oils can be filtered with removal efficiency of over 99% and dyes can be absorbed with removal efficiency of over 97%. Our results show that the GO-coated cotton can be regenerated and maintain this high removal efficiency after 50 separation cycles. We anticipate that underwater superoleophobic GO-coated cotton would be an ideal wastewater purification material for practical applications.