α-Fe2O3/Nb2O5 mixed oxide active for the photodegradation of organic contaminant in water: Factorial experimental design application and reaction mechanism investigation

Developing new high efficiency and stable catalysts for the degradation of organic compounds in effluents, under solar light has been a great challenge. In this regard, this work describes the synthesis of a alpha-Fe2O3/Nb2O5 mixed oxide by the Pechini method. The results of XRD and SEM/EDS confirmed the presence of Fe and Nb in the materials synthesized. The mixture of semiconductors oxides resulted in the material of greater specific surface area. The catalyst efficiency was verified through the photodegradation of methylene blue (MB) by the heterogeneous photo-Fenton reaction, under different experimental conditions using a 2(4) factorial experimental design with the central point in triplicate. The variables that most influenced the system response were the concentrations of MB, of the catalyst and of H2O2. The mechanism proposed followed Langmuir-Hinshelwood kinetics, with the greatest color removal percentage of 85%, under the optimal experimental conditions found. The mixed oxide exhibited greater efficiency when compared to the pure oxides synthesized since the synergic effect resulting from the mixture between Fe and Nb oxides led to the hematite activation. The catalyst remained stable even after five consecutive reaction cycles, unlike Nb2O5, suggesting its potential application in the environmental pollutants treatment.