Nb2O5 as efficient and recyclable photocatalyst for indigo carmine degradation

Heterogeneous photocatalysis is a significant green technology for application in water purification. The application of Nb₂O₅ catalyst for the photodegradation of contaminants is few reported in the literature. Thus, the Nb₂O₅ catalyst was characterized by SEM, FTIR, surface area and charge surface density. This catalyst was applied to degrade indigo carmine dye, which was compared with degradation catalyzed by TiO₂ and ZnO. Almost 100% of dye degradation occurred at 20, 45 and 90 min for TiO₂, ZnO and Nb₂O₅, respectively. The effect of Nb₂O₅ catalyst concentration, pH and ionic strength (μ) was investigated. The Nb₂O₅ activity increased at 0.7 g/L and for higher catalyst concentrations the degradation was kept constant. Degradation of indigo carmine dye catalyzed by Nb₂O₅ was improved at pH < 4.0 and μ = 0.05 mol/L. TiO₂, ZnO and Nb₂O₅ were recovered and re-applied in other nine reaction cycles. While TiO₂ and ZnO have an abrupt loss of their catalytic activity, Nb₂O₅ maintained 85% of catalytic activity after 10 reaction cycles.