Nanostructured niobium oxyhydroxide dispersed Poly (3-hydroxybutyrate) (PHB) films: Highly efficient photocatalysts for degradation methylene blue dye

[Display omitted] •The low content of niobium nanoparticles on the PHB (up 5wt%) led to approximately 100% conversion.•The niobium catalyst supported on the polymer films were easily removed from the solution after the reaction.•There was no leaching of active phase after successive reuses of the catalytic system. In this work, nanostructured niobium oxyhydroxide was dispersed over poly (3-hydroxybutyrate) (PHB), which is a biopolymer, for application as a photocatalyst using visible and UV light. PHB films with different amounts of niobium oxyhydroxide were characterized by diffuse UV–vis reflectance spectroscopy, FTIR-ATR and SEM. The characterizations showed particles of the niobium compound well-dispersed on the polymeric matrix, thus modifying the bandgap value, which improved the photocatalysis process. The material showed excellent catalytic activity (approximately 100% degradation) for the oxidation of methylene blue dye considering the reaction in a continuous flow bath. Moreover, the polymer films were easily removed from the solution after the reaction and reused several times while retaining their high activity. ESI–MS studies showed that the dye removal occurs by the formation of reaction intermediates due to the successive hydroxylation of the dye structure, confirming that the reaction took place improved by photocatalytic conditions.