The present study focused on the synthesis of nanostructured MgO via sonochemical method and its application as sonocatalyst for the decolorization of Basic Red 46 (BR46) dye under ultrasonic irradiation. The sonocatalyst was characterized using X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM) equipped with energy dispersive X-ray microanalysis (EDX). In the following, the sonocatalytic removal of the dye under different operational conditions was evaluated kinetically on the basis of pseudo first-order kinetic model. The reaction rate of sonocatalyzed decolorization using MgO nanostructures (12.7 × 10(-3) min(-1)) was more efficient than that of ultrasound alone (2.0 × 10(-3) min(-1)). The increased sonocatalyst dosage showed better sonocatalytic activity but the application of excessive dosage should be avoided. The presence of periodate ions substantially increased the decolorization rate from 14.76 × 10(-3) to 33.4 × 10(-3) min(-1). Although the application of aeration favored the decolorization rate (17.8 × 10(-3) min(-1)), the addition of hydrogen peroxide resulted in a considerable decrease in the decolorization rate (9.5 × 10(-3) min(-1)) due to its scavenging effects at specific concentrations. Unlike alcoholic compounds, the addition of phenol had an insignificant scavenging effect on the sonocatalysis. A mineralization rate of 7.4 × 10(-3) min(-1) was obtained within 120 min. The intermediate byproducts were also detected using GC-MS analysis.
A B S T R A C TIn the present study, ZnO nanoparticles immobilized on biosilica nanobiostructure were used for the photocatalytic degradation of Acid Red 88 (AR88) in aqueous phase. UV-induced ZnO/biosilica nanocomposite (78.84%) was more efficient than visible light-induced ZnO/biosilica nanocomposite (21.87%). The results of UV-vis diffuse reflectance spectra (DRS) indicated that the enhanced UV-vis absorption of the nanocomposite could be attributed to biosilica support. Increasing the adsorbent dosage from 0.1 to 1.5 g/L caused a sharp increase in the decolorization efficiency from 15.30 to 98.54%, respectively, while further increase in the amount of photocatalyst to 2 g/L led to a little drop in the decolorization efficiency, decreasing to 93.63%. Decreasing the initial AR88 concentration from 70 to 10 mg/L enhanced the apparent reaction rate constant (k ap ) from 0.0078 to 0.1579 min −1 and diminished the consumption of electrical energy (EE 0 ) from 2,813 to 139 kW h/m 3 , respectively. The decolorization and mineralization efficiency of 96.32 and 65.57% were obtained, respectively, thereby confirming an acceptable mineralization of AR88 within 30 min.
In the present study, ZnO nanostructures were synthesized and immobilized on the surface of diatomite via a simple sonochemical method for the photocatalytic degradation of formaldehyde in the aqueous phase. The characterization of as-prepared ZnO/diatomite nanocomposite was carried out by means of scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FT-IR). The photocatalysis of formaldehyde was favored at neutral pH. At a ZnO to diatomite ratio of 0.3, increasing the photocatalyst dosage from 0.2 to 1.5 g/L resulted in increasing the photocatalytic removal of formaldehyde from 37.51% to 88.05%. At a formaldehyde concentration of 100 mg/L, the complete removal of formaldehyde was attained within the reaction time of 50 min. A mineralization efficiency of 53% was achieved, thereby confirming a suitable mineralization of formaldehyde within the short reaction time of 60 min.
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