Synthesis of novel smart pH-sensitive modified silica nanoparticles for controllable oil-water separation

The newly designed superwettable polymers with external stimuli-responsive behavior have been greatly proposed a great research interest in the oil industry due to their fast and simple mechanism process. Herein, the development of the advanced silica-based pH-responsive materials linked with hydrophilic 3-(aminopropyl)triethoxysilane (APTES) and hydrophobic 1H,1H,2H,2H-perfluorooctyl-triethoxysilane (FOTS) chelating ligands have been designed for oil/water separation by a facile dip-coating process. This smart material can propose an excellent wettability conversion between superhydrophobicity-superoleophilicity and superhydrophilicity-underwater superoleophobicity, favorable stability, and durability, resulting in efficient separation for oil/water mixture. These properties were observed from the well-defined 3D porous surface of the smart materials when they were coated on the fabric surface. Furthermore, characterization described that the material compositions were chemically reacted and distributed throughout the smart fabric surface caused by the robust chemical interaction between the functional groups such as hydroxide, carboxylate, and silane. The water contact angle (pH≈10) was displayed at 167-160° and for acidic water (pH≈2) was ranging from 143-0° over 100 s denoting outstanding superhydrophobic and superhydrophilic features respectively. Underwater measurement pointed out that the smart fabric also has a great superoleophobicity for oil contact angle (150°). Moreover, the series of test results revealed a selective separation for oil/water system with efficacy > 98% and high oil flux ranging from 7200 to 7900 L.h⁻¹.m⁻² as well as water flux (5300–6200 L.h⁻¹.m⁻²). Therefore, these smart materials with fabric and non-fabric preparation have a direct environmental impact on real samples and they can largely dominate various oily wastewater/oil spills clean up.