Add time:08/05/2019         Source:sciencedirect.com

Semiconductors, such as zinc and niobium oxides, are suitable materials for photocatalytic and photo degradation reactions. Mixed zinc-niobium oxides have the same characteristics and could be used for the same purposes. Therefore, ZnO supported on Nb2O5 were synthesized by wet impregnation technique yielding mixed oxides of 5, 10, 20 and 50 ZnO wt.%, as well as pure zinc and niobium oxides, and calcined in muffle. Those oxides were characterized by XRD, DRS, XRF, textural analysis, BJH pore volume analysis and zeta potential. Solutions of bromophenol blue (BPB), a well-known indicator with main absorbance band at λ = 590 nm in pH > 4.3, and the catalysts, with bandgaps varying from 3.10 to 3.40 eV, were irradiated by UV light (λ = 254 nm) for 2 h for the photo degradation reaction. Aliquots were collected for dye concentration analysis and total organic carbon consumption every 30 min. Specific areas of 111 and 29 m2 g−1 were obtained for Nb2O5 and ZnO respectively, as well as intermediate values for the mixed oxides. Unexpected ZnNb2O6 was found by XRD and DRS. Zeta potential of −31.6 mV was obtained for Nb2O5 and it increased as ZnO was added until 7.1 mV for pure ZnO. All catalyzed reaction presented BPB degradations higher than 80% after 2 h (6 mg L−1 BPB and 20 mg catalyst). As zinc percentage increased, the mineralizing activity of the catalysts was increased because of the formation of ZnNb2O6 and ZnO and to reduction of repulsion factors up to total BPB degradation with pure ZnO within 1 h.

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