Structural analysis and visible light-activated photocatalytic activity of iron-containing soda lime aluminosilicate glass

Highlights: • Hematite was precipitated by heat treatment of iron aluminosilicate glass. • The hematite phase shows visible light photocatalytic activity. • We could prepare an effective photocatalyst from 'ubiquitous elements'. - Abstract: A relationship between structure and visible light-activated photocatalytic activity of iron-containing soda lime aluminosilicate (15Na₂O⋅15CaO⋅40Fe₂O₃⋅xAl₂O₃⋅(30−x)SiO₂) glass (xNCFAS) was investigated by means of ⁵⁷Fe-Mössbauer spectroscopy, X-ray diffractometry (XRD) and UV–visible light absorption spectroscopy (UV–VIS). The ⁵⁷Fe-Mössbauer spectrum of 11NCFAS glass measured after heat-treatment at 1000 °C for 100 min was composed of a paramagnetic doublet due to Fe^III(T_d) and two magnetic sextets due to regular hematite (α-Fe₂O₃) and hematite with larger internal magnetic field. X-ray diffraction patterns of heat-treated xNCFAS samples resulted in decrease of α-Fe₂O₃ and increase of Ca₂Fe₂₂O₃₃ or CaFe₂O₄ with alumina content. A quick decrease in methylene blue (MB) concentration from 15.6 to 4.7 μmol L⁻¹ was observed in the photocatalytic reaction test with 40 mg of heat-treated 11NCFAS glass under visible light-exposure. The largest first-order rate constant of MB decomposition (k) was estimated to be 9.26 × 10⁻³ min⁻¹. Tauc's plot yielded a band gap energy (E_g) of 1.88 eV for heat-treated 11NCFAS glass, which is smaller than previously reported E_g of 2.2 eV for α-Fe₂O₃. These results prove that addition of Al₂O₃ into iron-containing soda lime silicate glass is favorable for the preparation of improved visible light-photocatalyst with 'ubiquitous' elements