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Photocatalytic degradation of azo dye acid orange 7 using different light sources over Fe3+-doped TiO2 nanocatalysts

Han, F., Kambala, V.S.R., Dharmarajan, R., Liu, Y., Naidu, R.
Environmental technology & innovation 2018 v.12 pp. 27-42
azo dyes, catalysts, gas chromatography-mass spectrometry, hydrogen peroxide, inorganic ions, iron, irradiation, mineralization, models, molecular weight, monitoring, nitrates, oxalates, photocatalysis, reaction kinetics, solar radiation, sulfates, titanium dioxide, ultraviolet radiation, ultraviolet-visible spectroscopy
The photocatalytic degradation of a model azo dye acid orange 7 (AO7) by Fe³⁺-doped TiO2 nanocatalyst has been studied under UV, Visible (λ >400 nm) and solar light irradiation. The role of hydrogen peroxide to enhance the catalyst’s efficiency was examined. The reaction pathway of complete mineralization was investigated by monitoring the temporal evolution of reaction intermediates and low molecular weight organic acids (LMWOA) as final products in solution. These LMWOAs are oxidized eventually to inorganic ions such a nitrate, sulfate, oxalate etc, which are confirmed using GC–MS, UV–Vis and Ion Chromatographic analyses. The optimized conditions of photocatalytic degradation were obtained for degradation under different light source. The Fe3+-doped TiO2 showed high dye degradation efficiency under both UV (100%), visible (100%) and solar light (90%) which distinguishes Fe3+-doped TiO2 from materials in literature that are only efficient in particular light source for dye degradation. Furthermore, the Fe3+ doped titania photocatalysts are stable and can maintain performance up to 6 recycle use. Reaction kinetics for UV and solar light induced degradation followed first order reaction whereas visible light degradation followed a zero-order reaction.