Effect of a TiO₂ additive on the morphology and permeability of cellulose ultrafiltration membranes prepared via immersion precipitation with ionic liquid as a solvent

This work studies structure and properties of cellulose ultrafiltration membrane created by coupling of TiO₂ nanoparticles onto the cellulose matrix. Supported cellulose ultrafiltration membranes were cast out of cellulose-titanium dioxide-ionic liquid solution via phase inversion. The aim was to determine the effect of titanium dioxide concentration on cellulose membrane morphology and performance. 1-ethyl-3-methylimidazolium acetate ([emim][OAc]) was used to obtain cellulose-ionic liquid solutions at a concentration of 9 %. Thin polymeric films of 250 µm thickness were cast onto a non-woven PET support material with an adjustable casting knife. Pure deionized water was employed as a non-solvent agent. The obtained product morphology (cross-section) was examined with field emission scanning electron microscopy. Filtration tests were made to determine pure water flux and molar mass cut-off (MMCO). Filtration tests with humic acid solutions were carried out to provide initial indications of performance in industrial applications. The obtained results showed that addition of titanium dioxide particles in small amounts had a positive impact on virgin cellulose ultrafiltration membranes. Tested samples had good mechanical stability, stable pure water flux and a MMCO typical for commercial ultrafiltration membranes. In addition, all tested samples showed excellent fouling resistance to humic acid solutions. In general, incorporation of titanium dioxide particles into cellulose matrix membrane should be taken into account as a potential way to create ultrafiltration membranes with high operation performance.