Development of TiO2-coated YSZ/silica nanofiber membranes with excellent photocatalytic degradation ability for water purification

Abstract

Numerous reports have elucidated that TiO₂ nanoparticles (TiO₂-NPs) exhibit respectable photocatalytic degradation capacities due to their high specific surface areas. However, the current recovery process leads to a loss of TiO₂-NPs; therefore, there is a need to immobilize TiO₂-NPs on the substrate used. Herein, TiO₂-coated yttria-stabilized zirconia/silica nanofiber (TiO₂-coated YSZ/silica NF) was prepared by coating TiO₂ on the surface of YSZ/silica NF using a sol-gel process. The TiO₂ coating layer on the nanofiber surface improved the separation ability of the membrane as well as the photocatalytic degradation ability. The pore size of the TiO₂-coated YSZ/silica NF membrane was less than that of the pristine YSZ/silica NF membrane, and it rejected over 99.6% of the 0.5 μm polymeric particles. In addition, the TiO₂-coated YSZ/silica NF membrane showed excellent adsorption/degradation of humic acid (HA, 88.2%), methylene blue (MB, 92.4%), and tetracycline (TC, 99.5%). Six recycling tests were performed to evaluate the reusability of the TiO₂-coated YSZ/silica NF membrane. The adsorption/degradation efficiency for HA, MB, and TC decreased by 3.7%, 2.8%, and 2.2%, respectively. We thus verified the high separation ability, excellent photocatalytic degradation ability, and excellent reusability of the TiO₂-coated YSZ/silica NF membranes.