Abstract
Using Ti(OC4H9)4 as a precursor, Fe(NO3)3⋅9H2O as the source of iron, and NH4NO3 as the source of nitrogen, an Fe/N codoped TiO2 catalyst was prepared using a sol-gel hydrothermal method. The as-prepared powders were characterized using X-ray powder diffraction, electron spectroscopy for chemical analysis, Fourier-transform infrared spectroscopy, and ultraviolet-visible spectrophotometry. Fe and N codoping resulted in decreased crystallite size and increased specific surface area. Results of the photocatalytic degradation of acid orange 7 (AO7) in a continuous-flow fluidized-bed reactor indicated that the maximum decolorization (more than 90%) of AO7 occurred with the Fe/N-TiO2 catalyst (dosage of 20 g/L) when a combination of visible light irradiation for 10 h HRT (hydraulic retention time), and a heterogeneous system was used. The AO7 degradation efficiency was considerably improved by increasing the hydraulic retention time from 2.5 to 10 h or by reducing the initial AO7 concentration from 300 to 100 mg/L. The reaction rate increased with the light intensity and the maximum value occurred at 35 mW/cm2; moreover, the efficiency of the AO7 degradation increased when the pH decreased with maximum efficiency at pH 3.
Highlights
IntroductionAn estimated 2% of dyes produced annually are discharged as effluents from manufacturing plants, whereas 10% of dyes are discharged from textile and related industries [1]
Environmental pollution is a considerable concern in the modern world
We present a sol-gel hydrothermal method for the fabrication of Fe/N-TiO2 catalysts that respond to visible light
Summary
An estimated 2% of dyes produced annually are discharged as effluents from manufacturing plants, whereas 10% of dyes are discharged from textile and related industries [1]. Effluents generated from textile manufacturing contain a variety of pollutants characterized by deep coloration, high oxygen demand, high pH, large amounts of suspended solids, and low or nonbiodegradability [2,3]. Many methods have been tested to remove dyes from industrial effluents, including biological processes, adsorption, and coagulation. These methods still generate a large amount of sludge or solid waste that requires further treatment. Advanced oxidation processes are a suitable alternative to traditional methods for solving environmental problems caused by the discharge of textile-dyeing wastewater. Titanium dioxide (TiO2 ) is a heterogeneous photocatalysts and TiO2 based photocatalysis is a promising technique for wastewater treatment [4], especially for wastewater containing refractory organic compounds
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