Preparation of superhydrophobic-oleophilic quartz sand filter and its application in oil-water separation

It is imperative and challenging to develop environmentally acceptable and cost-effective materials which can readily separate stable emulsions like diesel-in-water emulsion stabilized with surfactants. Thus we attempt to prepare superhydrophobic-oleophilic nano-silica powders with an aggregate diameter of about 300 nm and a surface area of 231.2 m(2)/g by a surface modification method. Quartz sand surface are treated by as-obtained superhydrophobic-oleophilic silica nanoparticles containing only ca 0.4 wt% of organic functional groups to alter its intrinsic hydrophilicity to superhydrophobicity (with a water contact angle of 154.0 +/- 1.2 degrees and a sliding angle of about 4 degrees). The resultant superhydrophobic quartz sand exhibits oleophilicity and can act as a high performance filter to separate oil-water mixture with a good reusability, which makes it feasible for the oil film on the surface of water to be fully adsorbed by the treated quartz sand and easily separated from the water. In the meantime, the treated quartz sand filter can break the stability of surfactant stabilized oil/water emulsion, thereby facilitating the efficient separation of the oil phase from the aqueous phase. The as-prepared superhydrophobic and lipophilic quartz sand could be used as a cost-effective and environmentally acceptable filter for oil-water separation in petrochemical industry. (C) 2018 Elsevier B.V. All rights reserved.