Synthesis and characterisation of titania supported on bacterial cellulose films and evaluation of photocatalytic activity under solar irradiation

Abstract

Bacterial cellulose/titania (BCT) nanocomposite films were synthesised by depositing titania nanoparticles onto fibrillated bacterial cellulose (BC) hydrogels through thermal hydrolysis of titanium (IV) oxysulfate hydrate. Different amounts of TiO2 nano particles loading (25–80 wt% with respect to BC) were prepared by an in-situ method, and the samples were characterised by SEM, TEM, XRD, TGA, and nitrogen adsorption techniques. SEM and TEM analyses confirmed that titania particles, with a size of ∼40 nm, were strongly adhered to the fibrous network structure of BC. The crystallinity of BC and the formation of the nanocrystalline anatase phase of TiO2 in the BCT nanocomposite films were confirmed by XRD analysis. The specific surface area (SSA) of pristine BC was 56 m2/g, whereas all BCT nanocomposites showed higher SSA, with the composite containing 50 wt% of TiO2 loading (BC50T50) exhibiting the highest value of 80 m2/g. Photocatalytic activity was assessed by monitoring the degradation of rhodamine B (RhB) and methylene blue (MB) dyes at various concentrations. Colorimetric analysis was used for the quantitative evaluation of the photodegradation efficiencies of the BCT nanocomposite films. All the nanocomposites demonstrated significant photoactivity, among them BC50T50 film showed the highest degradation efficiency. BCT films could be reused for at least four consecutive cycles without a significant drop in photocatalytic efficiency. Additionally, BC50T50 composite film was prepared by an ex-situ synthesis approach, by mixing fibrillated BC and pre-synthesised TiO2 nanoparticles. The photocatalytic efficiency of the ex-situ synthesised BC50T50 composite was lower than its in-situ counterpart as the TiO2 particles formed large clusters around the cellulose fibers, reducing the effective surface area and active sites available for photocatalysis, eventually leading to lower degradation efficiency.