Adsorption et photodégradation du colorant indigo carmine en milieu aqueux en présence de TiO2/UV/O2 (Adsorption and photocatalytic degradation of indigo carmine dye in aqueous solutions using TiO2/UV/O2)

The adsorption and photocatalytic degradation of indigo carmine dye, selected as a model organic pollutant, has been investigated in aqueous suspension of semiconductor oxide TiO2 as photocatalyst under UV-lamp irradiation. TiO2 photocatalyst was produced in our laboratory using hydrolysis of titanium tetraisopropoxide (TTIP) at 600°C (TiO2 ″600°C″). The solid TiO2 ″600°C″ showed higher adsorption of indigo carmine (more efficient). The adsorption of dye on the semiconductor TiO2 ″600°C″ follows a Langmuir model and effect on initial rate of photodegradation. The influence of various parameters such as types of TiO2 (for comparison), initial concentration of dye, mass of the catalyst, pH, addition of oxidant hydrogen peroxide on the reaction rate was investigated and optimum conditions for maximum degradation was determined. The effect of some inorganic anions, such as Cl - , SO4 2- , HCO3 - , NO3 - and CH3COO - , commonly present in real effluents, on the photocatalytic degradation was also studied. TiO2 ″600°C″ exhibits much higher photocatalytic activity than commercial TiO2 photocatalysts (″Degussa P-25″, ″Millennium PC-500″, ″Hombicat-100″ and ″Fluka″). In the presence of TiO 2 ″600°C″ degradation is achieved within 30 min of illumination, while in the presence of TiO2 ″Degussa P-25″, TiO2 ″Millennium PC-500″, TiO2 ″Hombicat-100″ and TiO2 ″Fluka″, complete colour disappearance is accomplished in 120, 150, 180 and 330 min of light exposure, respectively. The degradation rates were found to be strongly influenced by all the above parameters. The disappearance of the organic molecule follows a pseudo-first kinetic order according to the Langmuir-Hinshelwood model. The kinetics was strongly enhanced in the presence of electron acceptor, H2O2, at low dosage. The inhibition of the anions for this reaction was in the order: NO3 -

Keywords:

• Indigo carmine
• Langmuir adsorption model
• Adsorption
• Aqueous solution
• Catalysis
• Photocatalysis
• Inorganic chemistry
• Photodegradation
• Reaction rate
• Chemistry

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