Effect of pH Variation on Synthesis and Photocatalytic Activity of Bi₂Fe₄O₉

The Pechini synthesis method, presents chemical homogeneity as its main advantage, enabling the desired phase to be obtained. This synthesis usually occurs at pH 7. In this study, Bi2Fe4O9 was synthesized using the Pechini method at different pHs (pH = 3, 5, 7, 8, 10 and 12) to verify if the pH conditions can influence in its photocatalytic activity. The materials obtained at different conditions were characterized by using X rays diffraction (XRD), UV/Vis diffuse reflectance and scanning electron microscopy by field emission (MEV/FEG).It was possible to synthesize the material under conditions already mentioned, but it was not observed significant differences in the chemical structure of the obtained materials from the characterization techniques. However, they presented a small variation in the band gap values, morphological aspects and photocatalytic activities. All the materials proved to be a good semiconductor, maintaining high degradation rates. The photocatalyst synthesized at pH 3 (BFO -1) presented a degradation rate of approximately 95% for the group chromophore and 93% for the aromatic group of the structure of the tartrazine yellow dye, proving to be a promising photocatalyst for industrial applications. This result is particularly important because BFO - 1 showed higher catalyst activity since the chromophore of the aromatic group was degraded. The highlights of this study is the synthesis of Bi2Fe4O9 performed at pH=3, since it reduces the quantity of reagents comparing to the conventional Pechini method and presented high photocatalytic activity.