“…The rate constants are in the same order of magnitude as reported by Zhu et al of 0.00559 min −1 for 50 mg L −1 methyl orange decolorization by visible light irradiation on SnO 2 /ZnO-immobilized chitosan film [22]. Likewise, the rate constants reported by Mittal et al of 0.00306 to 0.00746 min −1 for 10 mg L −1 crystal violet decolorization by visible light irradiation on Cu-doped ZnO were in the same range [20]. The results imply that the higher surface loading of ZnO under visible light irradiation can give more electron/hole pairs, as well as hydroxyl and superoxide radicals, singlet oxygen, and hydrogen peroxide, which contribute to the degradation of OG molecules and its chromophores.…”
An advanced oxidation process (AOP) utilizing immobilized zinc oxide (ZnO) photocatalyst was employed to decolorize and mineralize orange G (OG) azo dye in wastewater under solar and visible light irradiation. This AOP employed visible light and ZnO in a so-called Vis/ZnO process. Operating parameters, including ZnO dosage, initial OG concentration, pH, visible-light intensity, catalyst loaded area, and treatment volume were investigated to illustrate their influences on OG degradation and mineralization. From the results, neither visible light alone, nor the ZnO adsorption process could degrade or remove OG from wastewater. However, for the Vis/ZnO process, the higher ZnO dosage and visible light intensity are two major parameters to improve the OG degradation and total organic carbons (TOC) mineralization. The initial pH of 11 was the most effective pH condition on the OG degradation. The first-order rate constant is exponentially decreased from 0.025 to 0.0042 min −1 with the increase of the initial OG concentration and an empirical equation can be derived to estimate the first-order rate constant with a known initial OG concentration. In contrast, the first-order rate constant is linearly increased from 0.0027 to 0.0083 min −1 by increasing the visible light intensity. The results present that the Vis/ZnO process is an effective AOP for the degradation of OG in wastewater.
“…The rate constants are in the same order of magnitude as reported by Zhu et al of 0.00559 min −1 for 50 mg L −1 methyl orange decolorization by visible light irradiation on SnO 2 /ZnO-immobilized chitosan film [22]. Likewise, the rate constants reported by Mittal et al of 0.00306 to 0.00746 min −1 for 10 mg L −1 crystal violet decolorization by visible light irradiation on Cu-doped ZnO were in the same range [20]. The results imply that the higher surface loading of ZnO under visible light irradiation can give more electron/hole pairs, as well as hydroxyl and superoxide radicals, singlet oxygen, and hydrogen peroxide, which contribute to the degradation of OG molecules and its chromophores.…”
An advanced oxidation process (AOP) utilizing immobilized zinc oxide (ZnO) photocatalyst was employed to decolorize and mineralize orange G (OG) azo dye in wastewater under solar and visible light irradiation. This AOP employed visible light and ZnO in a so-called Vis/ZnO process. Operating parameters, including ZnO dosage, initial OG concentration, pH, visible-light intensity, catalyst loaded area, and treatment volume were investigated to illustrate their influences on OG degradation and mineralization. From the results, neither visible light alone, nor the ZnO adsorption process could degrade or remove OG from wastewater. However, for the Vis/ZnO process, the higher ZnO dosage and visible light intensity are two major parameters to improve the OG degradation and total organic carbons (TOC) mineralization. The initial pH of 11 was the most effective pH condition on the OG degradation. The first-order rate constant is exponentially decreased from 0.025 to 0.0042 min −1 with the increase of the initial OG concentration and an empirical equation can be derived to estimate the first-order rate constant with a known initial OG concentration. In contrast, the first-order rate constant is linearly increased from 0.0027 to 0.0083 min −1 by increasing the visible light intensity. The results present that the Vis/ZnO process is an effective AOP for the degradation of OG in wastewater.
“…Figure 8a shows the UV-visible absorption spectra of all the samples synthesized at 800 °C suggesting broad multiple absorption humps in the visible region, which may be associated with the presence of either oxide centers (NbO 2 and Nb 2 O 5 ) or continuous carbon network (highly disordered graphic carbon) in the nanocomposite powder samples 68 – 70 . The band gap for all the samples was calculated with the help of Tauc’s relationship between photon energy (hν) and absorption coefficient (α) as where A is a constant and ‘n’ depends on the type of transition containing values 0.5, 2.0, 1.5 and 3.0 corresponding to allowed direct, allowed indirect, forbidden indirect, and forbidden direct transitions, respectively 71 . Figure 8 ( a ) UV-Vis absorption spectra and ( b ) Tauc plot depicting dual band-gap corresponding to dual absorbance of all the samples synthesized at 800 °C.…”
Section: Resultsmentioning
confidence: 99%
“…The decolorization/degradation kinetics of photocatalytic reactions were studied with the help of pseudo first and second order law, which can be expressed as follows: where C 0 , C, K 1 and K 2 are the solution concentrations at irradiation time t = 0, at different times and pseudo first and second order rate constant (per minute), respectively 71 . A plot of −ln(C/C 0 ) vs. t (min) and t/C vs. t (min) as shown in Fig.…”
A facile carbothermal route was adopted to obtain niobium carbide nanoparticles (NPs) embedded in carbon network from Nb2O5 to study photocatalytic behavior. Optimization of synthesis parameters to obtain single phase NbC NPs has been successfully done. The phase identification, morphology and nature of carbon were determined with the help of X-ray diffraction, transmission electron microscopy (TEM) and Raman spectroscopy. X-ray photoelectron spectroscopy (XPS) suggested the presence of multiple oxidation states of Nb associated to NbC and NbCxOy centers on the surface of NPs. Due to the presence of NbCxOy on the surface of NPs, absorption under visible region of EM spectrum has been observed by UV-visible spectroscopy. Different organic dyes (RhB, MB and MO) were used to study the effect of holding time on the photocatalytic performance of as-synthesized samples. RhB dye was found to be the most sensitive organic molecule among all the considered dyes and degraded 78% in 120 min.
Herein, we demonstrate a simple hydrothermal route to synthesizing ZnSe/ZnO type II heterostructure using L‐cysteine as a capping agent. The use of nanomaterials in bioimaging and photocatalysis towards the degradation of Azophloxine dye is of potential interest. The synthesized ZnSe/ZnO nanomaterials were characterized by UV–Vis absorption spectroscopy, fluorescence spectroscopy, IR spectroscopy, scanning electron microscopy, transmission electron microscopy, X‐ray diffraction, and X‐ray photoelectron spectroscopy. It exhibits a strong sharp emission at 465 nm in fluorescence spectroscopy. The synthesized nanomaterials were used as an excellent fluorescence probe for imaging live‐cell bacteria such as E. coli and S. aureus compared with the commercial staining dye PI (propidium iodide). The synthesized ZnSe/ZnO possess more photo‐stability and showed excellent photocatalytic activity for the degradation of azophloxine dye under sunlight.
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