Superhydrophobic sand grains structured with aligned Cu(OH) 2 nano-needles for efficient oily water treatment

Abstract Desert sand as an abundant natural resource rarely has been reconsidered and reutilized due to its superhydrophilicity. Aiming at the combination of super-wettability with sand resource, we successfully design the aligned Cu(OH)2 nano-needles on the sand grain surfaces through a skillful strategy and conferred superhydrophobic properties on them in this study. The water contact angle and rolling angle are shown to be ~ 158° and ~ 6°, which break our traditional understanding towards desert sand, i.e., superhydrophilicity. More importantly, the selective superhydrophobic-superoleophilic wettability and the cavities between nano-needles and sand grains allow the sand to be a good candidate for efficient oily water treatment. The as-prepared superhydrophibic sand can not only absorb light oils from water surface, but separate heavy oils from oil/water mixtures. The speed of oil/water separation is up to 16,985 L m− 2 h− 1 when a 0.35 cm thickness of superhydrophobic sand layer is used. Significantly, it exhibits both high separation rate and high separation efficiency (> 99.5%). The as-prepared superhydrophobic sands are expected to become a new candidate of highly efficient oil/water separation material and to realize the reutilization of desert sand resource.