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1.
Environ Sci Pollut Res Int ; 24(7): 6361-6371, 2017 Mar.
Article in English | MEDLINE | ID: mdl-27475433

ABSTRACT

ZnO samples were prepared by sol-gel method applying a factorial design in order to improve the photocatalytic properties of the semiconductor oxide in the NO photooxidation reaction. The concentrations of zinc acetate and ammonium hydroxide were selected as critical variables in the synthesis of ZnO. Nine samples of ZnO were obtained as product of the factorial design and were characterized by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, diffuse reflectance spectroscopy, and N2 adsorption-desorption isotherms. The photocatalytic activity of ZnO samples was associated with the physical properties developed by each sample according to its respective conditions of synthesis. Some photocatalytic reaction parameters, such as mass of photocatalyst, irradiance, and relative humidity, were modified in order to evaluate its effect in the photocatalytic conversion of NO. As a relevant point, the relative humidity played an important role in the increase of the selectivity of the NO photooxidation reaction to innocuous nitrate ions when ZnO was used as photocatalyst.


Subject(s)
Environmental Pollutants/chemistry , Nitric Oxide/chemistry , Photochemical Processes , Zinc Oxide/chemistry , Zinc Oxide/chemical synthesis , Adsorption , Ammonium Hydroxide/chemistry , Catalysis , Environmental Pollutants/isolation & purification , Nitric Oxide/isolation & purification , Oxidation-Reduction , Zinc Acetate/chemistry
2.
Environ Sci Pollut Res Int ; 22(2): 792-9, 2015 Jan.
Article in English | MEDLINE | ID: mdl-24865501

ABSTRACT

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 %.


Subject(s)
Bismuth/chemistry , Indigo Carmine/chemistry , Molybdenum/chemistry , Photolysis , Water Purification , Edetic Acid/chemistry , Hot Temperature , Oxides
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