Facile preparation of superhydrophobic quartz sands with micro-nano-molecule hierarchical structure for controlling the permeability of oil and water phase

Although the present superhydrophobic sands have been demonstrated to be effective for oil/water separation and water storage, they still suffer from high-cost and difficult industrial application, resulting from their expensive raw materials, complicated fabrication procedures and fluorine-containing. In this paper, we demonstrated a facile method to synthesize stable superhydrophobic quartz sands by two step surface modification. SiO2 nanoparticles are bonding onto the surface of micro-sand skeletons (110-150 mu m) for conducting rounghneess structure, and then modify them with low-surface-energy hexadecyltrime-thoxysilane (HDTMS) to form a molecule protection layer. The as-prepared sands (HDTMS-sand@SiO2) exhibit a high WCA of 163 +/- 2.0 degrees, a low sliding angle of 5 degrees, and a oil contact angle of about 0 degrees. In addition, the HDTMS-sand@SiO2 retains superhydrophobicity after ultrasonication in petroleum ether, heating below 225 degrees C, irradiation with ultraviolet, and soaking in strong acidic and strong alkaline solutions, exhibiting sufficient stability against the harsh physicochemical environment of oil/water separation and some others. Particularly, superhydrophobic sands exhibit a outstanding drag reduction ability in a sand-filled core. Significantly, HDTMS-sand@SiO2 as a filter can leach oil phase and prevent water phase, which exhibits a good separation efficiency of oil/water mixture, water-in-oil and oil-in-brine emulsions. Thanks to the cheap and available raw materials, stable structure and high separation efficiency as well as low production cost ( < 150 USD per ton), this approach could find promising applications in the treatment of oily wastewater and petroleum development.