Customization of surface wettability of nano-SiO2 by coating Trimethoxy (vinyl)silane modifier for oil-water separation: Fabrication of metal-based functional superwetting nanomaterial, characterizations and performance evaluation

The wettability of nano-SiO2 surface was transformed from the inherent hydrophilicity to functional super-hyderophobicity by coating Trimethoxy (vinyl)silane modifier, and the resultant surface showed contrasting wettability for water and oil (Superhydrophobic and Superoleophilic), which is a desired characteristic for the membranes used in oil-water separation. Initially Trimethoxy (vinyl)silane coated SiO2 nanoparticles (TMVS@SiO2) were synthesized by hydrolysis and poly-condensation reactions, and this nano dispersion was spray coated on the annealed stainless-steel mesh surface, whose resulting hierarchical surface texture brought about the desired wettability, with the water-surface-air (theta WA) and oil-surface-air (theta OA) interfacial contact angles of 150 degrees and 0 degrees respectively. In addition to the wettability studies (contact angles), FTIR, morphological, and elemental characterizations of the TMVS@SiO2 coated surfaces were carried out to understand the alterations that have taken place on the TMVS@SiO2 surface that in turn rendered superhydrophobicity and super-oleophilicity to the surface. The FTIR absorption peaks indicate that after modifying SiO2 with TMVS, the -OH groups on SiO2 surface are clearly replaced by -CH3. The morphological studies indicated that modification of SiO2 leads to better cross-linking between coating composition and nanoparticles and EDS spectra and elemental mapping of the modified surface showed the presence of Si, O and C elements. Finally, this surface was tested for its efficiency and stability as a membrane in the process of separating oil and water from the oily water using gravity driven method. The oil-water separation efficiency was estimated to be 99% for this membrane and also it was found to be quite stable as the surface effectively retained this oil-water separation efficiency even after 10 cycles of separation process.