Chemical effects induced by gas–liquid jet flow

Author(s):  
Zhiliang Zhang ◽  
Jiaqi Lu ◽  
Bingqian Lv ◽  
Wei Liu ◽  
Shuyuan Shen ◽  
...  

The gas-liquid jet flow was proved to be capable of inducing chemical consequences which can lead to the decomposition of methylene blue (MB). The reaction process follows a pseudo-first-order kinetics....

2013 ◽  
Vol 634-638 ◽  
pp. 76-80
Author(s):  
Wei Hu ◽  
Shen Xin Li ◽  
Cheng Duan Wang

The decolourization of dye wastewater by persulfate was studied using methylene blue as a model dye wastewater. Effects of several parameters, such as dose of oxidant, ionic strength, pH, temperature and UV irradiation, were investigated in detail. The results showed that the decolourization reaction of methylene blue by persulfate could be fitted to a pseudo-first order kinetics model. In addition, when the oxidant amount used is 2 times of methylene blue, pH 3.43 and reaction temperature for 60°C, after uv light under the irradiation of 20 min, methylene blue decolorization rate can reach more than 98%. The results are useful for the treatment of dye wastewater.


2018 ◽  
Vol 43 (1) ◽  
pp. 26 ◽  
Author(s):  
Raul Fernando De Mello Peters ◽  
Pâmela Andréa Mantey dos Santos ◽  
Tiele Caprioli Machado ◽  
Diosnel Antonio Rodriguez Lopez ◽  
Ênio Leandro Machado ◽  
...  

The present work evaluates the use of ceramic material, produced with the aid of industrial waste through the Gel-Casting method, as a support for catalysts in the photocatalytic degradation of Methylene Blue. The analysis was carried out in a reactor containing UVC lamps through batch processing. The results show that the reaction of photocatalytic degradation of the dye presents pseudo-first order kinetics, with values of degradation between 60 and 70 %. The study evaluated the deactivation of the catalysts synthesized and supported in the ceramic material. In this case, it was observed that the larger the mass of deposited catalyst on the ceramic support, the longer the lifespan of the sample, since a larger mass takes longer to deactivate.


2020 ◽  
Vol 16 ◽  
Author(s):  
M. Alarjah

Background: Prodrugs principle is widely used to improve the pharmacological and pharmacokinetic properties of some active drugs. Much effort was made to develop metronidazole prodrugs to enhance antibacterial activity and or to improve pharmacokinetic properties of the molecule or to lower the adverse effects of metronidazole. Objective: In this work, the pharmacokinetic properties of some of monoterpenes and eugenol pro metronidazole molecules that were developed earlier were evaluated in-vitro. The kinetic hydrolysis rate constants and half-life time estimation of the new metronidazole derivatives were calculated using the validated RP-HPLC method. Method: Chromatographic analysis was done using Zorbbax Eclipse eXtra Dense Bonding (XDB)-C18 column of dimensions (250 mm, 4.6 mm, 5 μm), at ambient column temperature. The mobile phase was a mixture of sodium dihydrogen phosphate buffer of pH 4.5 and methanol in gradient elution, at 1ml/min flow rate. The method was fully validated according to the International Council for Harmonization (ICH) guidelines. The hydrolysis process carried out in an acidic buffer pH 1.2 and in an alkaline buffer pH 7.4 in a thermostatic bath at 37ºC. Results: The results followed pseudo-first-order kinetics. All metronidazole prodrugs were stable in the acidic pH, while they were hydrolysed in the alkaline buffer within a few hours (6-8 hr). The rate constant and half-life values were calculated, and their values were found to be 0.082- 0.117 hr-1 and 5.9- 8.5 hr., respectively. Conclusion: The developed method was accurate, sensitive, and selective for the prodrugs. For most of the prodrugs, the hydrolysis followed pseudo-first-order kinetics; the method might be utilised to conduct an in-vivo study for the metronidazole derivatives with monoterpenes and eugenol.


2021 ◽  
Vol 02 ◽  
Author(s):  
Emmanuel M. de la Fournière ◽  
Jorge M. Meichtry ◽  
Graciela S. Custo ◽  
Eduardo A. Gautier ◽  
Marta I. Litter

Background: Thiomersal (TM), a complex between 2-mercaptobenzoic acid (2-MBA) and ethylmercury (C2H5Hg+), is an antimicrobial preservative used in immunological, ophthalmic, cosmetic products, and vaccines. Objective: TM has been treated by UV/TiO2 photocatalysis in the presence or absence of oxygen at acidic pH. C2H5Hg+, 2-MBA, and 2-sulfobenzoic acid (2-SBA) were found as products. A 2-SBA photocatalytic treatment was undertaken to study sulfur evolution. Methods: Photocatalytic runs were performed using a UVA lamp (λmax = 352 nm), open to the air or under N2. A suspension of the corresponding TM or 2-SBA salt and TiO2 was prepared, and pH was adjusted. Suspensions were stirred in the dark for 30 min and then irradiated. TM, 2-MBA, 2-SBA, and C2H5Hg+ were quantified by HPLC, sulfur by TXRF, and the deposits on the photocatalyst were analyzed by chemical reactions. The mineralization degree was followed by TOC. Sulfate was determined using BaCl2 at 580 nm. Results: Photocatalytic destruction of TM and total C2H5Hg+ was complete under N2 and air, but TM degradation was much faster in air. The evolution of TM and the products followed a pseudo-first-order kinetics. Conclusion: TiO2-photocatalytic degradation is a suitable technique for the treatment of TM and its degradation products. In contrast to other organomercurial compounds, TM degradation is faster in the presence of O2, indicating that the oxidative mechanism is the preferred pathway. A significant TM mineralization (> 60%, NPOC and total S) was obtained. TM was more easily degraded than 2-SBA. Sulfate was the final product.


2020 ◽  
Author(s):  
Juliya Acha Parambil ◽  
Abdul Mujeeb V.M ◽  
S. Zh. Karazhanov ◽  
Jayaram Peediyekkal

Abstract The photocatalytic degradation of methylene blue in aqueous solutions is enhanced significantly by formulating multiphase TiO2/ZnO/Fe2O3 nanocomposites. The photocatalytic activity of unary TiO2, binary TiO2/ZnO, and ternary TiO2/ZnO/Fe2O3 compounds are compared and reported. Using TiO2/ZnO/Fe2O3, methylene blue degradation became rapid and the reaction followed first-order kinetics. The consequences of the phase transition, surface features, and optical properties are compared and elucidated. The reduced photoluminescence intensity and decreased optical band gap energy in tertiary compounds impose higher degradation of methylene blue under irradiation.


1996 ◽  
Vol 314 (3) ◽  
pp. 985-991 ◽  
Author(s):  
Subrata ADAK ◽  
Abhijit MAZUMDER ◽  
Ranajit K. BANERJEE

The plausible role of arginine and tyrosine residues at the active site of horseradish peroxidase (HRP) in aromatic donor (guaiacol) oxidation was probed by chemical modification followed by characterization of the modified enzyme. The arginine-specific reagents phenylglyoxal (PGO), 2,3-butanedione and 1,2-cyclohexanedione all inactivated the enzyme, following pseudo-first-order kinetics with second-order rate constants of 24 M-1·min-1, 0.8 M-1·min-1 and 0.54 M-1·min-1 respectively. Modification with tetranitromethane, a tyrosine-specific reagent, also resulted in 50% loss of activity following pseudo-first-order kinetics with a second-order rate constant of 2.0 M-1·min-1. The substrate, H2O2, and electron donors such as I- and SCN- offered no protection against inactivation by both types of modifier, whereas the enzyme was completely protected by guaiacol or o-dianisidine, an aromatic electron donor (second substrate) oxidized by the enzyme. These studies indicate the involvement of arginine and tyrosine residues at the aromatic donor site of HRP. The guaiacol-protected phenylglyoxal-modified enzyme showed almost the same binding parameter (Kd) as the native enzyme, and a similar free energy change (∆G´) for the binding of the donor. Stoicheiometric studies with [7-14C]phenylglyoxal showed incorporation of 2 mol of phenylglyoxal per mol of enzyme, indicating modification of one arginine residue for complete inactivation. The difference absorption spectrum of the tetranitromethane-modified against the native enzyme showed a peak at 428 nm, characteristic of the nitrotyrosyl residue, that was abolished by treatment with sodium dithionite, indicating specific modification of a tyrosine residue. Inactivation stoicheiometry showed that modification of one tyrosine residue per enzyme caused 50% inactivation. Binding studies by optical difference spectroscopy indicated that the arginine-modified enzyme could not bind guaiacol at all, whereas the tyrosine-modified enzyme bound it with reduced affinity (Kd 35 mM compared with 10 mM for the native enzyme). Both the modified enzymes, however, retained the property of the formation of compound II (one-electron oxidation state higher than native ferriperoxidase) with H2O2, but reduction of compound II to native enzyme by guaiacol did not occur in the PGO-modified enzyme, owing to lack of binding. No non-specific change in protein structure due to modification was evident from circular dichroism studies. We therefore suggest that the active site of HRP for aromatic donor oxidation is composed of an arginine and an adjacent tyrosine residue, of which the former plays an obligatory role in aromatic donor binding whereas the latter residue plays a facilitatory role, presumably by hydrophobic interaction or hydrogen bonding.


1950 ◽  
Vol 33 (6) ◽  
pp. 703-722 ◽  
Author(s):  
C. W. Sheppard ◽  
W. R. Martin

The exchange of potassium between cells and plasma of heparinized human blood has been studied in vitro using the radioactive isotope K42. The changes in cell and plasma specific activity are characteristic of a simple two-compartment system. The mean of seven determinations of the exchange rate at 38°C. is 1.8 per cent of the cellular potassium per hour. The results indicate that at 38°C. the rate is relatively insensitive to oxygenation or reduction of the hemoglobin, and to 1200 r of gamma radiation. With varying temperature the rate follows pseudo first order kinetics with a Q10 of 2.35. Below 15°C. the rate of loss of potassium exceeds the rate of uptake.


1991 ◽  
Vol 278 (2) ◽  
pp. 595-599 ◽  
Author(s):  
N Hirano ◽  
T Ichiba ◽  
A Hachimori

Treatment of the inorganic pyrophosphatase from thermophilic bacterium PS-3 with diethyl pyrocarbonate resulted in the almost complete loss of its activity, which followed pseudo-first-order kinetics. The presence of Mg2+ prevented the inactivation. Enzyme inactivated with diethyl pyrocarbonate was re-activated by hydroxylamine. The inactivation parallelled the amount of modified histidine residue, and a plot of the activity remaining against the amount of modified histidine residue suggested that the modification of one of two histidine residues totally inactivated the enzyme. The site involved was found to be located in a single lysyl endopeptidase-digest peptide derived from the ethoxy[14C]carbonylated enzyme. Amino acid analysis and sequence analysis of the peptide revealed that it comprised residues 96-119 of the inorganic pyrophosphatase from thermophilic bacterium PS-3. These results, when compared with those reported for the Escherichia coli and yeast enzymes, imply that His-118 of the inorganic pyrophosphatase from thermophilic bacterium PS-3 is located near the Mg(2+)-binding site and thus affects the binding of Mg2+.


2012 ◽  
Vol 65 (11) ◽  
pp. 1970-1974 ◽  
Author(s):  
C. Y. Kuo ◽  
C. Y. Pai ◽  
C. H. Wu ◽  
M. Y. Jian

This study applies photo-Fenton and photo-Fenton-like systems to decolorize C.I. Reactive Red 2 (RR2). The oxidants were H2O2 and Na2S2O8; Fe2+, Fe3+, and Co2+ were used to activate these two oxidants. The effects of oxidant concentration (0.3–2 mmol/L) and temperature (25–55 °C) on decolorization efficiency of the photo-Fenton and photo-Fenton-like systems were determined. The decolorization rate constants (k) of RR2 in the tested systems are consistent with pseudo-first-order kinetics. The rate constant increased as oxidant concentration and temperature increased. Activation energies of RR2 decolorization in the UV/H2O2/Fe2+, UV/H2O2/Fe3+, UV/Na2S2O8/Fe2+ and UV/Na2S2O8/Fe3+ systems were 32.20, 39.54, 35.54, and 51.75 kJ/mol, respectively.


Sign in / Sign up

Export Citation Format

Share Document