Fabrication of non-fluorinated hydrophilic-oleophobic stainless steel mesh for oil-water separation

Oil-water separation is a worldwide concern due to the increasing emissions of oil-contaminated industrial water, frequent oil spills and the general shortage of clean drinking water. In this study, hydrophilic/underwater superoleophobic stainless steel (SS) meshes were fabricated via a one-step solution-based coating method using methyltrimethoxysilane (MTMS). The dimensions of the meshes were varied to study their effect on wettability and separation efficiency. Coated meshes were then used for gravity-driven oil/water separation with oil-water mixtures and oil-water emulsions in which water passed through the meshes while oil was retained. Contact angles, fluid flux and separation efficiency were evaluated to determine the optimum mesh dimensions. XPS and ATR-FTIR were performed on the coated stainless steel surface to confirm the presence of silanol groups that are accountable for the resultant unique wetting properties. After sand impact durability testing, the treated meshes were still able to separate oil-water mixtures with high separation efficiency and water recovery rates, despite the presence of residual sand particles.