Nanocrystalline Bi2O3–B2O3– (MoO3 or V2O5) glass-ceramic systems for organic pollutants degradation

Fixation of photocatalyst in glass matrix would solve the problem of photocatalyst recovery. In this study, the system 30 Bi2O3, 20 B2O3 and 50 (MoO3 or V2O5), was used for the preparation and stabilization of the photoactive phases of both bismuth molybdate β-Bi2Mo2O9 and monoclinic–scheelite BiVO4 in a glassy matrix. Proper heat-treatment schedule, based on differential thermal analysis (DTA) results, has been applied to improve the crystallinity of the prepared glass–ceramics. The applied heat-treatment program showed a significant effect on the size of the formed crystals, especially in samples with molybdenum content. For instance, one-step heat-treatment (500°C/2 h) improves the crystallinity of the material than two-step heat-treatment (355°C/1 h+400°C/2 h). It was also noticed that the amount of glassy matrix relative to crystalline part in case of vanadium-contained samples is much more than that in the corresponding molybdenum-contained samples. The prepared samples were used for the degradation of Red SPD Cotton dye in order to assess their photocatalytic activity. All molybdenum contained samples showed a promising photocatalytic activity. On contrary, vanadium-contained samples were inactive suggesting that most of photoactive crystals are in the bulk of materials.