Synthesis and Characterization of Ti-Nb2O5 Catalysts for Discoloration Reaction of Bromophenol Blue and Indigo Carmine Dyes

Abstract

This work investigated the photodegradation of bromophenol blue (BPB) and indigo carmine (IC) dye under UV–Visible light using pure oxides of titanium and niobium, as well as TiO2-Nb2O5 oxides containing 0.5, 2.5 and 5 wt% of TiO2, prepared by wet impregnation of Nb2O5 with Ti tert-butoxide under inert atmosphere. The results of XRD and Raman spectroscopy showed the presence of anatase TiO2 phase and T-Nb2O5 phase with orthorhombic structure in the pure TiO2 and Nb2O5 oxides, respectively. The Nb2O5 oxides doped with TiO2 presented a T-Nb2O5 phase, but there was no formation of TiNb2O7. TiO2 anatase was observed in the mixed oxide with higher Ti content (5 wt% TiO2). A zeta potential analysis showed positive surface charge values for titanium oxide and negative for niobium oxide and mixed oxides. The addition of up to 5 wt% of the TiO2 fold the activity of Nb2O5 in the discoloration of both dyes. Pure TiO2 exhibits higher initial activity, which could be related to its positive PZC and higher attraction to sulphonic groups present in the dyes. Despite of the lower initial rate, 2.5 and 5% TiNb catalysts achieved full degradation of the dyes after 4 h of reaction.