•Sol-gel synthesized and heat-treated 40FexAlSi samples with ‘x’ of 10, 15, and 20 resulted in the precipitation of fayalite, hematite and maghemite NPs with photocatalytic properties.•The corresponding degradation rate constant k, following the first-order reaction kinetics, was 14.89 × 10−2 min−1 for 40Fe2O3-15Al2O3-45SiO2 sample.•The presence of various crystalline phases that contain iron ions in mixed-valence states favors the formation of continuous pathways for uninterrupted polaronic transport which enhances an increase in DC conductivity.•Electrical conductivity and photocatalytic activity of the composites increase with the alumina content. The glass samples with the composition of 40Fe2O3-xAl2O3-(60−x)SiO2 were prepared by sol-gel method. The samples were characterized by XRD, 80 K 57Fe Mössbauer spectroscopy, TEM, FTIR and impedance spectroscopy. In the glass samples with less than 10% alumina, fayalite and hematite were crystallized by addition of hercynite. Whereas nanoparticles of hematite (α-Fe2O3) and maghemite (γ-Fe2O3) doped with Al were confirmed with the increase of alumina contents (15% and 20%). The glass samples exhibit the electronic conduction which is explained by the polaronic conduction mechanism. It is noticed that the catalysts containing a mixture of hematite and maghemite nanoparticles showed higher photocatalytic degradation of Rhodamine B dye than those containing hematite alone. It is suggested from the characterizations of newly developed iron-containing aluminosilicate glass samples that the materials with several bandgaps and without dissolving itself should be developed in the future for water purification under visible light irradiation.