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H2O2 Oxidation (h2o2 + oxidation)
Selected AbstractsKinetic study of the manganese-based catalytic hydrogen peroxide oxidation of a persistent azo-dyeJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 2 2010Chedly Tizaoui Abstract BACKGROUND: The discharge of synthetic dyes by the textile industry into the environment poses concerns due to their persistence and toxicity. New efficient treatment processes are required to effectively degrade these dyes. The aim of this work was to study the degradation of a persistent dye (Drimarene Brilliant Reactive Red K-4BL, C.I.147) using H2O2 oxidation catalysed by an Mn(III)-saltren catalyst and to develop a kinetic model for this system. RESULTS: Dye oxidation with H2O2 was significantly improved by the addition of the catalyst. As the pH was increased from 3 to 10, the oxidation rates increased significantly. The kinetic model developed in this study was found to adequately explain the experimental results. In particular, dye oxidation can be described at high pH by pseudo-first-order kinetics. A Michaelis,Menton type equation was developed from the model and was found to adequately describe the effect of H2O2 and catalyst concentrations on the apparent pseudo-first-order rate constant. Optimum catalyst and H2O2 concentrations of 500 mg L,1 and 6.3 g L,1, respectively, were found to give maximum reaction rates. CONCLUSION: Catalytic H2O2 oxidation was found to be effective for the removal of persistent dye and the results obtained in this work are of significance for design and scale-up of a treatment process. Copyright © 2009 Society of Chemical Industry [source] Catalytic resonance scattering spectral determination of ultratrace horseradish peroxidase using rhodamine SLUMINESCENCE: THE JOURNAL OF BIOLOGICAL AND CHEMICAL LUMINESCENCE, Issue 3 2009Zhiliang Jiang Abstract A highly sensitive and selective resonance scattering spectral assay was proposed for the determination of horseradish peroxidase (HRP), based on its catalytic effect on the H2O2 oxidation of KI to form I3,. The I3, combined respectively with rhodamine (Rh) dye such as rhodamine S (RhS), rhodamine 6G (Rh6G), rhodamine B (RhB) and butyl-rhodamine B (b-RhB), to form association particles (Rh-I3)n. The four Rh systems all exhibit a stronger resonance scattering (RS) peak at 424 nm. For the RhS, Rh6G, RhB and b-RhB systems, HRP concentration in the range of 3.2 × 10,12 to 4.8 × 10,9, 2 × 10,11 to 3.2 × 10,9, 1.6 × 10,11 to 3.2 × 10,9 and 1.6 × 10,11 to 4 × 10,9 g/mL was linear to its RS intensity at 424 nm, with a detection limit of 2.2 × 10,12, 2.5 × 10,12, 4.4 × 10,12 and 2.6 × 10,12 g/mL, respectively. This RhS system was most sensitive and stable, and was applied for the determination of HRP in the hepatitis B surface antibody labeling HRP and water samples, with satisfactory results. Copyright © 2009 John Wiley & Sons, Ltd. [source] Apoptosis-Inducing High .CHEMMEDCHEM, Issue 10 2008NO Concentrations Are Not Sustained Either in Nascent or in Developed Cancers Abstract Nitric oxide (.NO) induces apoptosis at high concentrations by S-nitrosating proteins such as glyceraldehyde-3-phosphate dehydrogenase. This literature analysis revealed that failure to sustain high . NO concentrations is common to all cancers. In cervical, gastric, colorectal, breast, and lung cancer, the cause of this failure is the inadequate expression of inducible nitric oxide synthase (iNOS), resulting from the inhibition of iNOS expression by TGF-,1 at the mRNA level. In bladder, renal, and prostate cancer, the reason for the insufficient . NO levels is the depletion of arginine, resulting from arginase overexpression. Arginase competes with iNOS for arginine, catalyzing its hydrolysis to ornithine and urea. In gliomas and ovarian sarcomas, low . NO levels are caused by inhibition of iNOS by N -chlorotaurine, produced by infiltrating neutrophils. Stimulated neutrophils express myeloperoxidase, catalyzing H2O2 oxidation of Cl, to HOCl, which N-chlorinates taurine at its concentration of 19,mM in neutrophils. In squamous cell carcinomas of the skin, ovarian cancers, lymphomas, Hodgkin's disease, and breast cancers, low . NO concentrations arise from the inhibition of iNOS by N -bromotaurine, produced by eosinophil-peroxidase-expressing infiltrating eosinophils. Eosinophil peroxidase catalyzes the H2O2 oxidation of Br, to HOBr, which N-brominates taurine to N -bromotaurine at its concentration of 15,mM in eosinophils. In microvascularized tumors, the . NO concentration is further depleted; . NO is rapidly consumed by red blood cells (RBCs) through S-nitrosation of RBC glutathione and hemoglobin, and by oxidation to nitrate by RBC oxyhemoglobin. Angiogenesis-inhibiting antibodies are currently used to treat cancers; their mode of action is not, as previously thought, reduction of the tumor O2 or nutrient supply. They actually decrease the loss of . NO to RBCs. [source] | ||||||||||