Facile fabrication of superhydrophilic and underwater superoleophobic surfaces on cotton fabrics for effective oil/water separation with excellent anti-contamination ability

Freshwater contamination by spilling oil and scarcity have progressively exasperated the global water crisis. Developing a facile method to remediate polluted water as well as converting the abundant oily wastewater to freshwater has become a matter of urgency. Here we developed a cotton fabric based membrane (ZnO@CF) with special wettability and excellent anti-contamination ability by using zinc chloride aqueous solution as a micro-dissolving agent and zinc source, and using gaseous ammonia as alkali source. Micro/nano structure zinc oxide was in-situ grown on the fibers as superhydrophilic matter as well as enabling the membrane with photocatalytic property. The resulting cotton fabrics (ZnO@CF) are superhydrophilic and superoleophobic underwater with a water droplet spread of 0.3 s and an underwater oleophobic angle of 156.3°. ZnO@CF could separate different oil-water mixtures with separation efficiency higher than 99.3% and a permeate flux up to 940 L m−2 h−1 solely driven by gravity. After three cycles of separation, ZnO@CF still maintained a separation efficiency of about 99.2% and little flux variety, suggesting its fantabulous stability for repeated application. Impressively, ZnO@CF also demonstrated great anti-contamination abilities, including resistance to oil contamination and degradation of dyes staining. Even immersed in the dye aqueous solution, ZnO@CF was capable to separate oil-water mixture containing dyestuff after UV assisted degradation, and did not show any worsening in separation performances. These obvious advantages together with the potential for facile production make the membrane promising toward efficient oil-water separation in practical applications.