Fluorine-Induced Superhydrophilic Ti Foam with Surface Nanocavities for Effective Oil-in-Water Emulsion Separation

Recently, oil/water separation has attracted intensive attention because of frequent crude oil spill accidents and the increasing amount of industrial wastewater. Ti-based materials are nontoxic and environment-friendly for oil/water separation; however, there is little attention focused on this field. In the present work, we introduce, for the first time, surface -O-Ti-F groups onto Ti foam by a simple anodization in a fluorine-containing electrolyte to form a superhydrophilic membrane for oil-in-water emulsion separation, which was proven to be excellent with the assistance of surface nanocavities. The water permeability of anodized Ti foam is elevated by about 10 times as compared to that of the original one, and the oil/water separation efficiency is above 99% with good anticorrosive properties. In addition, this fluorine-induced superhydrophilicity can be applied to metals and semimetals for many other applications such as self-cleaning, surface modification of catalysts, removal of heavy metal ions, etc.