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

A relationship between structure and visible light-activated photocatalytic activity of iron-containing soda lime aluminosilicate (15Na2O15CaO40Fe2O3xAl2O3(30x)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 FeIII(Td) and two magnetic sextets due to regular hematite (a- Fe2O3) and hematite with larger internal magnetic field. X-ray diffraction patterns of heat-treated xNCFAS samples resulted in decrease of a-Fe2O3 and increase of Ca2Fe22O33 or CaFe2O4 with alumina content. A quick decrease in methylene blue (MB) concentration from 15.6 to 4.7 lmol 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 (Eg) of 1.88 eV for heat-treated 11NCFAS glass, which is smaller than previously reported Eg of 2.2 eV for a-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.