Using titanium dioxide nanoparticle-deposited whey protein isolate amyloid fibrils to photocatalyze the degradation of methylene blue

Background: Titanium dioxide nanoparticles (TiO 2 NPs) have been widely used in photocatalytic reactions, but their tendency to aggregate reduces their photocatalytic activity. Recent studies have suggested that whey protein isolate amyloid fibrils (WPI-AFs) serve as promising catalyst carriers due to their structural stability and high surface area. This study is aimed at applying WPI-AFs to improve the dispersibility and photocatalytic activity of TiO 2 NPs. Methods: One-dimensional composites, TiO 2 NP-deposited WPI-AFs (TiO 2 NP/WPI-AFs), were synthesized via the hydrothermal method. The concentration of TiO 2 NPs on WPI-AFs ' surface was determined through inductively coupled plasma optical emission spectroscopy (ICP-OES). TiO 2 NP/WPI-AFs were characterized via transmission electron microscopy (TEM), Fourier -transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD). In addition, the photocatalytic activities of bare TiO 2 NPs and TiO 2 NP/WPI-AFs were assessed by monitoring the degradation of methylene blue (MB) using UV-vis spectrophotometry. Significant findings: TiO 2 NP/WPI-AFs showed improved dispersibility and narrow band gap compared to TiO 2 NPs. The photocatalytic activity of TiO 2 NP/WPI-AFs was superior to that of bare TiO 2 NPs. The mechanism of TiO 2 NP/ WPI-AFs photocatalyzed-MB degradation was examined by fitting the kinetic data with Langmuir - Hinshelwood and modified Elovich models. The results of activation parameters showed that TiO 2 NP/WPI-AFs lowers the activation energy, and the photocatalytic MB degradation is an endothermic and energetically unfavorable reaction.