Synthesis and Characterization of Ti-Nb2O5Catalysts for Discoloration Reaction of Bromophenol Blue and Indigo Carmine Dyes

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-Nb(2)O(5)oxides containing 0.5, 2.5 and 5 wt% of TiO2, prepared by wet impregnation of Nb(2)O(5)with Ti tert-butoxide under inert atmosphere. The results of XRD and Raman spectroscopy showed the presence of anatase TiO(2)phase and T-Nb(2)O(5)phase with orthorhombic structure in the pure TiO(2)and Nb(2)O(5)oxides, respectively. The Nb(2)O(5)oxides doped with TiO(2)presented a T-Nb(2)O(5)phase, but there was no formation of TiNb2O7. TiO(2)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 TiO(2)fold the activity of Nb(2)O(5)in the discoloration of both dyes. Pure TiO(2)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.