New insights on the UV/TiO2 photocatalytic treatment of thiomersal and its 2-sulfobenzoic acid product

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.

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Photodegradation of diclofenac in aqueous solution by simulated sunlight irradiation: kinetics, thermodynamics and pathways

Water Science & Technology ◽

10.2166/wst.2017.075 ◽

2017 ◽

Vol 75 (9) ◽

pp. 2163-2170 ◽

Cited By ~ 6

Author(s):

N. Zhang ◽

J. M. Li ◽

G. G. Liu ◽

X. L. Chen ◽

K. Jiang

Keyword(s):

High Performance ◽

Degradation Products ◽

Photobacterium Phosphoreum ◽

Degradation Pathways ◽

Simulated Sunlight ◽

Liquid Chromatography Mass Spectrometry ◽

Sunlight Irradiation ◽

First Order ◽

First Order Kinetics ◽

Pseudo First Order

Diclofenac (DCF) is one of the most frequently detected pharmaceuticals in various water samples. This paper studied the effects of aquatic environmental factors (pH, temperature and dissolved organic matter) on photodegradation of DCF under simulated sunlight. The results demonstrate that degradation pathways proceed via pseudo first-order kinetics in all cases and the photodegradation of DCF by simulated sunlight. Thermodynamic study indicated that the photodegradation course is spontaneous, exothermic and irreversible. The rate constant gradually increased when the pH increased from 3 to 5, then decreased when the pH increased from 5 to 8, and finally increased when the pH further increased from 8 to 12. Humic acid inhibited the photodegradation of DCF. Three kinds of main degradation products were observed by high performance liquid chromatography/mass spectrometry and the degradation pathways were suggested. A toxicity test using Photobacterium phosphoreum T3 Sp indicated the generation of some more toxic products than DCF.

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Decolourization of Alizarin Red by Persulfate

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.610-613.300 ◽

2012 ◽

Vol 610-613 ◽

pp. 300-305

Author(s):

Shen Xin Li ◽

Wei Hu ◽

Cheng Duan Wang

Keyword(s):

Ionic Strength ◽

Uv Irradiation ◽

Degradation Products ◽

Kinetics Model ◽

Dye Wastewater ◽

Alizarin Red ◽

First Order ◽

First Order Kinetics ◽

Pseudo First Order

The decolourization of dye wastewater by persulfate was studied using alizarin red 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 alizarin red by persulfate could be fitted to a pseudo-first order kinetics model. In addition, no degradation products were observed during the decolourization of alizarin red by persulfate. The results are useful for the treatment of dye wastewater.

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Degradation and mineralization of violet-3B dye using C-N-codoped TiO2 photocatalyst

Environmental Engineering Research ◽

10.4491/eer.2019.196 ◽

2019 ◽

Vol 25 (4) ◽

pp. 529-535 ◽

Cited By ~ 1

Author(s):

Reza Audina Putri ◽

Safni Safni ◽

Novesar Jamarun ◽

Upita Septiani ◽

Moon-Kyung Kim ◽

...

Keyword(s):

Reaction Rate ◽

Sol Gel ◽

Organic Dye ◽

Halogen Lamp ◽

Acidic Ph ◽

Initial Concentration ◽

First Order ◽

First Order Kinetics ◽

Pseudo First Order ◽

Catalyst Dosage

The present study investigated the photodegradation of synthetic organic dye; violet-3B, without and with the addition of C-N-codoped TiO2 catalyst using a visible halogen-lamp as a light source. The catalyst was synthesized by using a peroxo sol-gel method with free-organic solvent. The effects of initial dye concentration, catalyst dosage, and pH solution on the photodegradation of violet-3B were examined. The efficiency of the photodegradation process for violet-3B dye was higher at neutral to less acidic pH. The kinetics reaction rate of photodegradation of violet-3B dye with the addition of C-N-codoped TiO2 followed pseudo-first order kinetics represented by the Langmuir-Hinshelwood model, and increasing the initial concentration of dyes decreased rate constants of photodegradation. Photodegradation of 5 mg L-1 violet-3B dye achieved 96% color removal within 240 min of irradiation in the presence of C-N-codoped TiO2 catalyst, and approximately 44% TOC was removed as a result of the mineralization.

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The effect of photosensitizer on diclofenac photodegradation under simulated sunlight

Water Science & Technology ◽

10.2166/wst.2012.590 ◽

2013 ◽

Vol 67 (2) ◽

pp. 418-423 ◽

Cited By ~ 1

Author(s):

N. Zhang ◽

G. G. Liu ◽

H. J. Liu ◽

Y. L. Wang ◽

T. Li

Keyword(s):

High Performance ◽

Degradation Products ◽

Degradation Pathways ◽

Simulated Sunlight ◽

Liquid Chromatography Mass Spectrometry ◽

First Order ◽

Chemical Structures ◽

First Order Kinetics ◽

Photodegradation Rate ◽

Pseudo First Order

This paper studies the effect of photosensitizer (acetone, H2O2, surfactant and pigment) on photodegradation of diclofenac (DCF) under simulated sunlight. The results demonstrate that degradation pathways proceed via pseudo first-order kinetics in all cases. The photodegradation rate was found to increase with increasing acetone and H2O2. Surfactant and pigment inhibited the photodegradation of DCF. Finally, four kinds of main degradation products were observed by high performance liquid chromatography/mass spectrometry and their chemical structures were suggested.

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In-vitro Kinetic Hydrolysis Study of Metronidazole Derivatives with Carvacrol and Eugenol Using Validated RP-HPLC Method

Current Pharmaceutical Analysis ◽

10.2174/1573412916999200529123151 ◽

2020 ◽

Vol 16 ◽

Author(s):

M. Alarjah

Keyword(s):

Half Life ◽

Hplc Method ◽

Hydrolysis Rate ◽

First Order ◽

First Order Kinetics ◽

Rp Hplc ◽

Pharmacokinetic Properties ◽

Pseudo First Order ◽

Kinetic Hydrolysis

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.

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Chemical effects induced by gas–liquid jet flow

Reaction Chemistry & Engineering ◽

10.1039/d1re00519g ◽

2022 ◽

Author(s):

Zhiliang Zhang ◽

Jiaqi Lu ◽

Bingqian Lv ◽

Wei Liu ◽

Shuyuan Shen ◽

...

Keyword(s):

Methylene Blue ◽

Jet Flow ◽

Reaction Process ◽

Liquid Jet ◽

First Order ◽

First Order Kinetics ◽

Chemical Effects ◽

Pseudo First Order

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....

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Probing the active site residues in aromatic donor oxidation in horseradish peroxidase: involvement of an arginine and a tyrosine residue in aromatic donor binding

Biochemical Journal ◽

10.1042/bj3140985 ◽

1996 ◽

Vol 314 (3) ◽

pp. 985-991 ◽

Cited By ~ 19

Author(s):

Subrata ADAK ◽

Abhijit MAZUMDER ◽

Ranajit K. BANERJEE

Keyword(s):

Active Site ◽

Native Enzyme ◽

Tyrosine Residue ◽

Tyrosine Residues ◽

First Order ◽

First Order Kinetics ◽

Aromatic Donor ◽

Pseudo First Order ◽

Modified Enzyme ◽

Compound Ii

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.

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CATION EXCHANGE BETWEEN CELLS AND PLASMA OF MAMMALIAN BLOOD

The Journal of General Physiology ◽

10.1085/jgp.33.6.703 ◽

1950 ◽

Vol 33 (6) ◽

pp. 703-722 ◽

Cited By ~ 72

Author(s):

C. W. Sheppard ◽

W. R. Martin

Keyword(s):

Exchange Rate ◽

Radioactive Isotope ◽

Specific Activity ◽

Compartment System ◽

First Order ◽

First Order Kinetics ◽

Mammalian Blood ◽

The Mean ◽

Pseudo First Order

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.

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The role of histidine-118 of inorganic pyrophosphatase from thermophilic bacterium PS-3

Biochemical Journal ◽

10.1042/bj2780595 ◽

1991 ◽

Vol 278 (2) ◽

pp. 595-599 ◽

Cited By ~ 3

Author(s):

N Hirano ◽

T Ichiba ◽

A Hachimori

Keyword(s):

Thermophilic Bacterium ◽

Complete Loss ◽

Inorganic Pyrophosphatase ◽

Histidine Residue ◽

First Order ◽

Diethyl Pyrocarbonate ◽

Lysyl Endopeptidase ◽

First Order Kinetics ◽

Pseudo First Order

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+.

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Effects of oxidant concentration and temperature on decolorization of azo dye: comparisons of UV/Fenton and UV/Fenton-like systems

Water Science & Technology ◽

10.2166/wst.2012.095 ◽

2012 ◽

Vol 65 (11) ◽

pp. 1970-1974 ◽

Cited By ~ 6

Author(s):

C. Y. Kuo ◽

C. Y. Pai ◽

C. H. Wu ◽

M. Y. Jian

Keyword(s):

Rate Constant ◽

Rate Constants ◽

Azo Dye ◽

Activation Energies ◽

First Order ◽

First Order Kinetics ◽

Oxidant Concentration ◽

Decolorization Efficiency ◽

Pseudo First Order ◽

Reactive Red 2

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.

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