Green synthesis of amorphous and gamma aluminum oxide nanoparticles by tragacanth gel and comparison of their photocatalytic activity for the degradation of organic dyes

The current study concentrates on Al₂O₃ nanoparticles (NPs) synthesis using tragacanth gel as a biotemplate source by the means of sol–gel method at different calcination temperatures. The synthesized catalysts were characterized by XRD, FTIR, FESEM, and EDX. The XRD analysis indicated that the catalyst calcined at 500 °C has amorphous and the one calcined at 900 °C has gamma phase. The comparison of photocatalytic activity of both amorphous and gamma Al₂O₃ NPs was investigated under visible light irradiation, considering their effects on the degradation of organic dyes, for instance direct black 122 (DB122) and reactive yellow 145 (RY145). The studied effects include initial dye concentration, photocatalyst dosage, and visible light irradiation on dye degradation. Comparison of photocatalytic activity of mentioned photocatalysts exhibited better degradation of a-Al₂O₃ than that of γ-Al₂O₃. The results stated that a-Al₂O₃ catalyst could remove 97% of the direct black 122, whereas with γ-Al₂O₃, only 30% dye was removed. Regarding RY145, 95 and 26% degradation was observed, respectively.