Heterogeneous photocatalytic degradation of nile blue dye in aqueous BiOCl suspensions

Abstract

Bismuth oxychloride (BiOCl) was synthesized by hydrolysis method. Several analytical tools such as X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Brunauer–Emmett–Teller (BET) surface area, X-ray photoelectron spectroscopic, and energy-dispersive spectroscopic techniques were used to characterize the sample. The prepared material had average pore diameter of about 7–10nm and the BET surface area of BiOCl was 40 m2 g−1. The analysis of hydroxyl radicals (•OH) formation was performed by fluorescence technique. The intermediates and the final products of degradation were detected by high-performance liquid chromatography–photodiode array-electrospray ionization-mass spectrometry (HPLC–ESI-DAD-MS) technology. The degradation of nile blue (NB) dye was mainly attributed to the destruction of the conjugated structure, and after that the intermediates were transformed into small molecules mainly phenol, aniline, etc., which were mineralized to water and carbon dioxide. During three recycles, the catalyst did not exhibit any significant loss of photocatalytic activity, confirming that the photocatalyst is essentially stable. The NB oxidation was evaluated by the decrease in total organic carbon (TOC) content. The formation of NO3− and the evolution of CO2 revealed complete mineralization of aqueous NB during the photocatalytic process by this photocatalyst.