Photocatalytic degradation of indigo carmine by hydrothermally synthesized Bi₂MoO ₆ in presence of EDTA.

Bi2MoO6 oxide was synthesized by hydrothermal reaction in the presence of EDTA under different experimental conditions (time of reaction and EDTA concentration) in order to obtain materials with specific textural properties. It was determined that the addition of EDTA influences the final physical properties of Bi2MoO6. The photocatalytic activity of Bi2MoO6 samples was evaluated in the degradation reaction of indigo carmine (IC) in aqueous solution under solar radiation type. The best results as photocatalyst were obtained with the sample hydrothermally synthesized at 150 ºC for 4h in presence of a 0.031 M EDTA solution. This sample was able to whiten a solution of IC in a 94% after 120 min of lamp irradiation with t 1/2 = 31 min. In general, the samples prepared with lower concentrations of EDTA were the best photocatalysts. A gradual decrease in the activity was observed in the samples prepared with the same EDTA concentration as was increased in the reaction time. Beyond differences in morphology and textural properties of the samples prepared, the presence of EDTA by-products on the samples and the decomposition degree of it were important factors in determining the activity of the photocatalysts. Analysis of total organic carbon (TOC) of samples irradiated for 100 h confirmed that Bi2MoO6 oxide is able to mineralize the complex organic molecule of IC to CO2 and H2O in 55 %.