- Study of catalytic reduction and photodegradation of methylene blue by heterogeneous catalyst
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The photocatalytic degradation of methylene blue is investigated in aqueous solution containing CoS/nanoAl-MCM-41 photocatalyst under visible light. The catalyst is characterized by X-ray diffraction (XRD), UV-vis diffused reflectance spectra (UV-vis DRS) and transmission electron microscopy (TEM) techniques. The effect of CoS, nanoAl-MCM-41 support and different wt% of CoS over the support on the photocatalytic degradation and influence of parameters such as CoS loading, catalyst amount, pH and initial concentration of methylene blue on degradation are evaluated. Hypsochromic effects (i.e. blue shifts of spectral bands) resulting from N-demethylation of the dimethylamino group in methylene blue occurs in presence of CoS/nanoAl-MCM-41 under ambient condition. Meanwhile, the bleaching of methylene blue MB, by sulfide ion, in an aqueous solution is studied in the presence nanoAl-MCM-41 catalyst. In the presence of sulfide ions, MB is bleached to its colorless leuco (LMB) and MBH 2+ forms. In an acidified solution (pH 2+ form is observed. Using nanoAl-MCM-41 with encapsulated CoS nanoparticles only causes demethylation of MB in aqueous solution.
- Sohrabnezhad
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- Layered manganates from soft-templates: Preparation, characterization and enhanced dye demethylation capabilities
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A soft-template method for the synthesis of layered manganate (K xMnO2, birnessites) compounds with a relatively good control at the nanoscale regime on the number of octahedral layers (thickness) is described. The soft-template method is based on the stabilization of reverse micelles at moderate temperatures and the optimization of parameters to modulate the size of the templates while still preserving their stability during the formation of layered manganates. Degradation experiments of a model system (methylene blue) using the birnessites here reported have shown efficient demethylation in the absence of oxidants for aqueous suspensions made of non-dried birnessites containing the fewest number of layers. The observed strong thickness and aggregation dependence (i.e. dependence on exposed surfaces) for demethylation explains why particulate birnessites have only been considered for dye sequestration and not as an efficient demethylation agent in the absence of oxidants. Finally, when compared to electrodeposited thin films, the higher loading capabilities of the colloidal suspensions here prepared have made it possible to demethylate larger amounts of methylene blue at a similar time.
- Tartaj, Pedro
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- Enhanced photo Fenton-like activity by effective and stable Al–Sm M-hexaferrite heterogenous catalyst magnetically detachable for methylene blue degradation
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Nano-compositing technologies are getting enhanced attention due to unique catalytic and separation activity with advanced characteristics for dye wastewater treatment. In this study, novel easily separable Ba–Sr based Al–Sm substituted M-hexaferrites (BASF-NPs) were fabricated as a highly effective heterogenous photo-Fenton-like catalysts via sol-gel route. The analytical techniques were applied to investigate BASF-NPs characteristics such as TGA, XRD, FTIR, XPS, SEM/TEM/EDS, UV–Vis, BET and VSM analysis. The results revealed that all fabricated BASF-NPs showed excellent photo-Fenton-like catalytic performance towards Methylene Blue (MB) degradation. Virtually complete degradation of an initial 10 mg/L MB was achieved under optimal conditions (i.e. 16 mM H2O2 and 0.25 g/L BASF-NPs) within 140 min of UV-irradiated reaction time and followed pseudo-first order reaction kinetic at the rate of 6.514 × 10?2 min?1. Similar degradation trend was noticed at various pH levels (pH 3–12), signifying the efficiency of the NPs at wide pH range. Due to the intrinsic magnetic nature of BASF-NPs, it was readily recoverable by external magnetic field and exposed strong capacity for dye removal treatment. The photo-catalysts retained its performance after four consecutive cycles, indicating robust reusability and excellent stability.
- Ashraf, Ghulam Abbas,Rasool, Raqiqa Tur,Hassan, Muhammad,Zhang, Lanting
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supporting information
(2019/12/30)
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- A facile synthesis of Mn3O4/Fe3O 4 superparamagnetic nanocomposites by chemical precipitation: Characterization and application in dye degradation
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Degradation of methylene blue (MB) is investigated using Mn 3O4 as an oxidant. Discrete Mn3O4 particles and Mn3O4/Fe3O4 nanocomposites are synthesized via coprecipitation by using air as an oxidant in the absence and presence of previously synthesized magnetite nanoparticles, respectively. Characterization results show that superparamagnetic magnetite nanoparticles of ~10 nm were synthesized. The Mn3O4 synthesis in the presence of these magnetite nanoparticles favors the formation of a pure, highly ordered Mn3O4/Fe3O 4 superparamagnetic nanocomposite, which can be separated by an external magnetic field. This nanocomposite is applied to the oxidative decolorization of methylene blue (MB) and is capable of catalyzing the complete N-demethylation of MB, forming thionine as the final product and removing 93% of the dye in approximately 1 h.
- Silva, Gabriela C.,Ciminelli, Virginia S.T.,Ferreira, Angela M.,Pissolati, Nathalia C.,Paiva, Paulo Renato P.,López, Jorge L.
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p. 544 - 551
(2013/11/19)
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- Kinetic studies on oxidations of leucomethylene blue and leucothionine by iron (III) in aqueous solution
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The reaction kinetics and mechanism of the oxidations of leucomethylene blue (MBH) and leucothionine (TH) by iron (III) sulfate in aqueous solution were studied spectrophotometrically by the stopped-flow technique. MBH and TH, which were freshly prepared by photoreduction of methylene blue and thionine, respectively, with ascorbic acid were used in the kinetic measurements. The pseudo-first-order rate constants (kobsd) show kinetic saturation at high initial concentrations of iron (III) sulfate for MBH and TH. It was found that the reciprocal of kobsd increases linearly with increase in the reciprocal of [Fe3+]0. A broad absorption band was observed on mixing MBH and Fe3+ solutions at low temperatures, and this was attributed to a charge-transfer complex between MBH and Fe3+. The effects of Fe2+ ion and L-(+)-ascorbic acid on the rates of oxidation were also investigated. A small kinetic isotope effect on the oxidation rate for MBH was observed. The results can be explained by a general mechanism with stepwise electron-proton-electron transfers with the formation of a complex between reactants. Copyright
- Liu, Yingjin,Yamamoto, Shunzo,Sueishi, Yoshimi
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p. 194 - 200
(2007/10/03)
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