- A facile synthesis of Mn3O4/Fe3O 4 superparamagnetic nanocomposites by chemical precipitation: Characterization and application in dye degradation
-
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.
-
-
Read Online
- Photochromic properties of the molecule Azure A chloride in polyvinyl alcohol matrix
-
In the present work, isomerization, photophysical properties and heat conductivity of the substance Azure A chloride (AZAC): 3-amino-7-(dimethlamino)phenothiazin-5-ium chloride under the action of UV radiation in the presence of polyvinyl alcohol (PVA) matrix was studied using the Hartree-Fock (HF) and Density Functional Theory (DFT) methods. The electronic absorption spectra of AZAC in dimethylformamide (DMF) solution and in aqueous medium before and after UV radiation were calculated. The nature of absorption bands of AZAC and its tautomeric prototropic form with the transfer of the electron (AZAC1) in the visible and near UV spectral regions was interpreted. The solvent effect on the absorption spectrum of the AZAC has established. The comparison of measured FTIR, UV-Visible data allowed assignments of major special features of title molecules. The frontier molecular orbital HOMO-LUMO have been also presented that shows the charge transfer interactions taking place within these molecules. The excitation energies for both molecules AZAC and AZAC1 have also been calculated. The experimental as well as theoretical investigations of azure molecule have a close agreement and it gives other important clues about the properties of the system. Anisotropy of thermal conductivity in PVA-films containing AZAC and AZAC1 were also measured.
- Shahab, Siyamak,Filippovich, Liudmila,Kumar, Rakesh,Darroudi, Mahdieh,Borzehandani, Mostafa Yousefzadeh,Gomar, Maryam,Hajikolaee, Fatemeh Haji
-
-
Read Online
- HPLC-MS and UV–Visible Coupled Analysis of Methylene Blue Photodegradation by Hydrothermally Grown ZnO Nanowires
-
Photocatalysis is an efficient and promising method to purify water. Numerous studies have been dedicated to demonstrate its efficiency on several hazardous compounds, derived from various industries. However, even if the degradation of such products has been extensively studied, obtaining information on their photodegradation pathway is still challenging, leading to concerns about the innocuousness of the treated water. In this study, the authors use ZnO nanowires (ZnO NWs), to photodegrade a solution of the commonly used organic dye methylene blue (MB) under ultraviolet (UV) irradiation, followed simultaneously by UV-visible (UV-vis) spectrometry and high-performance liquid chromatography coupled with mass spectrometry (HPLC-MS). Combining these two methods real-time information on the photodegradation efficiency and degradation mechanism are given. The HPLC-MS analysis allows us to confidently identify three reaction intermediates of the MB degradation: Azure A, B and C, as well as spot three other compounds, with uncertain formulas, leading to the presented hypothesis on the beginning of the MB degradation pathway. While the UV-visible analysis shows a total degradation of MB after 2 h of photodegradation, the HPLC-MS analysis indicates that some MB remain in the solution. Its quantity is calculated to be 14 μg L?1, which is harmless to humans.
- Martin, Nathan,Leprince-Wang, Yamin
-
-
- Uncatalyzed and V(V)-Catalyzed Reaction of Methylene Blue with Potassium Bromate in Aqueous Sulfuric Acid
-
The uncatalyzed and V(V)-catalyzed kinetics of reaction between methylene blue (phenotiazinium, 3,7-bis(dimethylamino)-,chloride) and acidic bromate has been studied monitoring the absorbance of methylene blue (MB) at 665 nm.Both the reactions involved competitive and sequential steps, having slow reaction in the initial stages.A rapid reaction followed after an induction time.For the two reactions, the orders with respect to the reactants are the same: second order with H+, first order each with respect to bromate ion and MB.In addition, the catalyzed reaction had first order dependence on catalyst concentration.In both the reactions HOBr is found to be the reaction intermediate.HOBr competed with bromate ion in the depletion of MB to give an intermediate, possibly phenothiazin-5-ium, 3-methylamino-7-dimethylamino-, chloride.The intermediate is further oxidized possibly by HOBr in fast step to final product, phenothiazin-5-ium, 3-amino-7-dimethylamino, -chloride.The stoichiometric ratios of MB to bromate are 2:3.The dual role of bromide ion as an inhibitor at low concentration and as an autocatalyst at higher concentrations above a certain critical concentration in the reaction mechanism is discussed.
- Muthakia, G. K.,Jonnalagadda, S. B.
-
p. 4751 - 4756
(2007/10/02)
-