Immobilization of Bi2WO6 on Polymer Membranes for Photocatalytic Removal of Micropollutants from Water – A Stable and Visible Light Active Alternative

Abstract

In this work, bismuth tungstate Bi₂WO₆ is immobilized on polymer membranes to photocatalytically remove micropollutants from water as an alternative to titanium dioxide TiO₂. A synthesis method for Bi₂WO₆ preparation and its immobilization on a polymer membrane is developed. Bi₂WO₆ is characterized using X-ray diffraction and UV–vis reflectance spectroscopy, while the membrane undergoes analysis through scanning electron microscopy, X-ray photoelectron spectroscopy, and degradation experiments. The density of states calculations for TiO₂ and Bi₂WO₆, along with PVDF reactions with potential reactive species, are investigated by density functional theory. The generation of hydroxyl radicals OH^• is investigated via the reaction of coumarin to umbelliferone via fluorescence probe detection and electron paramagnetic resonance. Increasing reactant concentration enhances Bi₂WO₆ crystallinity. Under UV light at pH 7 and 11, the Bi₂WO₆ membrane completely degrades propranolol in 3 and 1 h, respectively, remaining stable and reusable for over 10 cycles (30 h). Active under visible light with a bandgap of 2.91 eV, the Bi₂WO₆ membrane demonstrates superior stability compared to a TiO₂ membrane during a 7-day exposure to UV light as Bi₂WO₆ does not generate OH^• radicals. The Bi₂WO₆ membrane is an alternative for water pollutant degradation due to its visible light activity and long-term stability.