Degradation of emerging contaminants: Effect of thermal treatment on nb2o5 as photocatalyst

This study describes the use Nb2O5 catalysts - calcined at different temperatures (373-873 K) - in the photocatalytic degradation reaction of four contaminants of emerging concern: acetylsalicylic acid (ASA), 17 alpha-ethinylestradiol (EE2), ibuprofen (IBP) and paracetamol (PAR). The photocatalysts were characterized by different techniques - N2 adsorption/desorption, photoacoustic spectroscopy (PAS), Fourier Transform Infrared (FT-IR) and X-ray diffraction (XRD) - and applied in the photocatalytic degradation tests. Among the tested catalysts, non-calcined Nb2O5 showed the highest photocatalytic activity. The characterization results indicated that this catalyst presented an amorphous (non-crystalline) structure, low band gap and the highest surface area (SBET = 182 m2 g-1). A design of experiments (DoE) methodology was applied in order to verify the effects of pH (4-10) and catalyst concentration (0.5-1.5 g L-1) in the four pollutants removal using the non-calcined Nb2O5. According to the Experimental Design Analysis, a statistically significant linear effect with a negative coefficient was observed for pH in EE2, IBP and PAR photocatalytic degradation. Tests to verify the influence of the presence compounds together in the degradation reaction of each contaminant, suggested that the photocatalytic degradation of IBP occurs predominantly through the action of radicals O2 center dot-, with minor contribution from HO center dot.