PVA/SiO2-coated stainless steel mesh with superhydrophilic-underwater superoleophobic for efficient oil-water separation

Polyvinyl alcohol (PVA)/SiO2-modified stainless steel mesh was fabricated to use as an underwater superoleophobic membrane for a high effective separation of oily wastewater. The fabricated membranes showed superhydrophilic properties in air and underwater superoleophobicity. The underwater oil contact angles of modified membranes were up to 156.6 degrees. The maximum separation efficiency of PVA/SiO2-modified stainless steel mesh for hexane, cyclohexane, diesel, soybean oil, lubricating oil, and silicone oil was 99.4%, 99.3%, 99.6%, 99.0%, 98.6%, and 98.0%, respectively. In addition, the PVA/SiO2-coated stainless steel mesh still retained high separation efficiency (above 95%) for hexane after 100 separation cycles. This membrane also exhibited durable underwater superoleophobicity in the pH range from 4 to 10. The membranes were prepared in a single step by the dip-coating method. The PVA/SiO2-coated meshes had high efficiency, high flux, and good reusability. The modified membranes could effectively separate oil from water without depending on any extra power. This membrane could be a promising product for the cleanup of oil spills and oily wastewater.