scholarly journals Comparison of the degradation of molecular and ionic ibuprofen in a UV/H2O2 system

2018 ◽  
Vol 77 (9) ◽  
pp. 2174-2183 ◽  
Author(s):  
Rongkui Su ◽  
Liyuan Chai ◽  
Chongjian Tang ◽  
Bo Li ◽  
Zhihui Yang
Keyword(s):  
Quantum Yield ◽  
Rate Constant ◽  
Degradation Rate ◽  
Molecular Form ◽  
Degradation Kinetics ◽  
Dominant Role ◽  
Radical Scavenging ◽  
Operating Conditions ◽  
Direct Photolysis ◽  
H2o2 System

Abstract The advanced oxidation technologies based on •OH can effectively degrade the pharmaceutical and personal care products under operating conditions of normal temperature and pressure. In this study, direct photolysis of ibuprofen (IBU) is slow due to the relatively low molar extinction coefficient and quantum yield. Compared to direct photolysis, the degradation kinetics of IBU was significantly enhanced in the UV/H2O2 system, mainly by •OH radical mediated oxidation. In the UV/H2O2 system, the degradation rate of ionic IBU was slightly faster than that of the molecular form. Kinetic analysis showed that the second-order reaction rate constant of ionic IBU (5.51 × 109 M−1 s−1) was higher than that of the molecular form (3.43 × 109 M−1 s−1). The pseudo first-order rate constant for IBU degradation (kobs) increased with increasing H2O2 dosage. kobs can be significantly decreased in the presence of natural organic matter (NOM), which is due to (i) NOM radical scavenging effects (dominant role) and (ii) UV absorption. The degradation of IBU was inhibited by HCO3–, which was attributed to its scavenging effect. Interestingly, when NO3– was present in aqueous solution, a slight increase in the degradation rate was observed, which was due to NO3– absorbing photons to generate •OH at a low quantum yield. No obvious effects were observed when SO42 and Cl− were present.

scholarly journals Photocatalytic Degradation of Monolinuron and Linuron in an Aqueous Suspension of Titanium Dioxide Under Simulated Solar Irradiation

2007 ◽  
Vol 20 (2) ◽  
pp. 163-172 ◽  
Author(s):  
Razika Zouaghi ◽  
Abdennour Zertal ◽  
Bernard David ◽  
Sylvie Guittonneau
Keyword(s):  
Photocatalytic Degradation ◽  
Degradation Rate ◽  
Ph Value ◽  
Degradation Kinetics ◽  
Aqueous Suspension ◽  
Operating Conditions ◽  
Solar Irradiation ◽  
Point Of Zero Charge ◽  
Degradation Rates ◽  
Simulated Solar Irradiation

Abstract The photocatalytic degradation of two phenylurea herbicides, monolinuron (MLN) and linuron (LN), was investigated in an aqueous suspension of TiO2 using simulated solar irradiation. The objective of the study was to compare their photocatalytic reactivity and to assess the influence of various parameters such as initial pesticide concentration, catalyst concentration and photonic flux on the photocatalytic degradation rate of MLN and LN. A comparative study of the photocatalytic degradation kinetics of both herbicides showed that these two compounds have a comparable reactivity with TiO2/simulated sun light. Under the operating conditions of this study, the photocatalytic degradation of MLN and LN followed pseudo first-order decay kinetics. The kobs values indicated an inverse dependence on the initial herbicide concentration and were fitted to the Langmuir-Hinshelwood equation. Photocatalytic degradation rates increased with TiO2 dosage, but overdoses did not necessarily increase the photocatalytic efficiency. The degradation rate of MLN increased with radiant flux until an optimum at 580 W m‑2 was reached and then decreased. Under these conditions, an electron-hole recombination was favored. Finally, the photocatalytic degradation rate depended on pH, where an optimum was found at a pH value close to the pH of the point of zero charge (pH = 6).

scholarly journals pH effect on stability and kinetics degradation of nitazoxanide in solution

2020 ◽  
Vol 4 (1) ◽  
pp. 12-17
Author(s):  
Fábio Barbosa ◽  
Leonardo Pezzi ◽  
Julia Sorrentino ◽  
Martin Steppe ◽  
Nadia Volpato ◽  
...  
Keyword(s):  
Rate Constant ◽  
Degradation Product ◽  
Degradation Rate ◽  
Degradation Kinetics ◽  
Ph Effect ◽  
Degradation Rate Constant ◽  
Main Degradation Product ◽  
Wide Ph Range ◽  
The Stability ◽  
Ph Range

Stability studies correspond to a set of tests designed to assess changes in the quality of a given drug over time and under the influence of a number of factors. Among these factors, pH plays an important role, due to the catalytic effect that hydronium and hydroxide ions can play in several reactions. In the present study, the degradation kinetics of nitazoxanide was evaluated over a wide pH range, and the main degradation product generated was identified by LC-MS/MS. Nitazoxanide showed first-order degradation kinetics in the pH range of 0.01 to 10.0 showing greater stability between pH 1.0 and 4.0. The degradation rate constant calculated for these pH was 0.0885 x 10-2 min-1 and 0.0689 x 10-2 min-1, respectively. The highest degradation rate constant value was observed at pH 10.0 (0.7418 x 10-2 min-1) followed by pH 0.01 (0.5882 x 10-2 min-1). A major degradation product (DP-1) was observed in all conditions tested. Through LC-MS/MS analysis, DP-1 was identified as a product of nitazoxanide deacetylation. The effect of pH on the stability of nitazoxanide and the kinetic data obtained contribute to a better understanding of the intrinsic stability characteristics of nitazoxanide.

scholarly journals Detecting and Quantifying Polyhaloaromatic Environmental Pollutants by Chemiluminescence-Based Analytical Method

Molecules ◽  
2021 ◽  
Vol 26 (11) ◽  
pp. 3365
Author(s):  
Ben-Zhan Zhu ◽  
Miao Tang ◽  
Chun-Hua Huang ◽  
Li Mao
Keyword(s):  
Analytical Method ◽  
Degradation Kinetics ◽  
Environmental Pollutants ◽  
Environmental Implications ◽  
Future Studies ◽  
System A ◽  
Quinoid Structure ◽  
Fenton System ◽  
Generating System ◽  
H2o2 System

Polyhaloaromatic compounds (XAr) are ubiquitous and recalcitrant in the environment. They are potentially carcinogenic to organisms and may induce serious risks to the ecosystem, raising increasing public concern. Therefore, it is important to detect and quantify these ubiquitous XAr in the environment, and to monitor their degradation kinetics during the treatment of these recalcitrant pollutants. We have previously found that unprecedented intrinsic chemiluminescence (CL) can be produced by a haloquinones/H2O2 system, a newly-found ●OH-generating system different from the classic Fenton system. Recently, we found that the degradation of priority pollutant pentachlorophenol by the classic Fe(II)-Fenton system could produce intrinsic CL, which was mainly dependent on the generation of chloroquinone intermediates. Analogous effects were observed for all nineteen chlorophenols, other halophenols and several classes of XAr, and a novel, rapid and sensitive CL-based analytical method was developed to detect these XAr and monitor their degradation kinetics. Interestingly, for those XAr with halohydroxyl quinoid structure, a Co(II)-mediated Fenton-like system could induce a stronger CL emission and higher degradation, probably due to site-specific generation of highly-effective ●OH. These findings may have broad chemical and environmental implications for future studies, which would be helpful for developing new analytical methods and technologies to investigate those ubiquitous XAr.

scholarly journals In situ degradability of dry matter and fibrous fraction of sorghum silage

2016 ◽  
Vol 38 (2) ◽  
pp. 171 ◽  
Author(s):  
Renê Ferreira Costa ◽  
Daniel Ananias de Assis Pires ◽  
Marielly Maria Almeida Moura ◽  
José Avelino Santos Rodrigues ◽  
Vicente Ribeiro Rocha Júnior ◽  
...  
Keyword(s):  
Experimental Design ◽  
Dry Matter ◽  
Degradation Rate ◽  
Degradation Kinetics ◽  
Grain Sorghum ◽  
Dual Purpose ◽  
Ruminal Degradability ◽  
Sorghum Silage ◽  
Kinetics Of

This study aimed to evaluate in situ degradability and degradation kinetics of DM, NDF and ADF of silage, with or without tannin in the grains. Two isogenic lines of grain sorghum (CMS-XS 114 with tannin and CMS-XS 165 without tannin) and two sorghum hybrids (BR-700 dual purpose with tannin and BR-601 forage without tannin) were ensiled; dried and ground silage samples were placed in nylon bags and introduced through the fistulas. After incubation for 6, 12, 24, 48, 72 and 96 hours, bags were taken for subsequent analysis of fibrous fractions. The experimental design was completely randomized with 4 replicates and 4 treatments and means compared by Tukey’s test at 5% probability. As for the DM degradation rate, silage of CMSXS165without tannin was superior. Silages of genotypes BR700 and CMSXS 114 with tannin showed the highest values of indigestible ADF (59.54 and 43.09%). Regarding the NDF, the potential degradation of silage of CMSXS165 line without tannin was superior. Tannin can reduce ruminal degradability of the dry matter and fibrous fractions. 

Hg(63P1)-sensitized decomposition of HNCO vapor and HNCO–H2 mixtures; the reaction of hydrogen atoms with HNCO

1968 ◽  
Vol 46 (4) ◽  
pp. 527-530 ◽  
Author(s):  
N. J. Friswell ◽  
R. A. Back
Keyword(s):  
Quantum Yield ◽  
Cross Section ◽  
Initial Step ◽  
Primary Process ◽  
Hydrogen Atoms ◽  
Direct Photolysis ◽  
A Value ◽  
The Cross

The Hg(63P1)-sensitized decomposition of HNCO vapor has been briefly studied at 26 °C with HNCO pressures from about 3 to 30 Torr. The products detected were the same as in the direct photolysis, CO, N2, and H2. The quantum yield of CO was appreciably less than unity, compared with a value of 1.5 in the direct photolysis under similar conditions. From this and other observations it is tentatively concluded that a single primary process occurs:[Formula: see text]From a study of the mercury-photosensitized reactions in mixtures of HNCO with H2, it was concluded that hydrogen atoms react with HNCO to form CO but not N2. The initial step is probably addition to form NH2CO. From the competition between reaction [1] and the corresponding quenching by H2, the cross section for reaction [1] was estimated to be 2.3 times that of hydrogen.

scholarly journals How Poloxamer Addition in Hyaluronic-Acid-Decorated Biodegradable Microparticles Affects Polymer Degradation and Protein Release Kinetics

2021 ◽  
Vol 11 (16) ◽  
pp. 7567
Author(s):  
Teresa Silvestri ◽  
Barbara Immirzi ◽  
Giovanni Dal Poggetto ◽  
Paola Di Donato ◽  
Valentina Mollo ◽  
...  
Keyword(s):  
Hyaluronic Acid ◽  
Degradation Rate ◽  
Degradation Kinetics ◽  
Dynamic Balance ◽  
Release Kinetics ◽  
Slight Modification ◽  
Gel Permeation Chromatography ◽  
Protein Release ◽  
Polymeric Microparticles ◽  
Biodegradable Microparticles

Polymeric microparticles (MPs) designed for the intravitreal administration of therapeutic proteins result in a prolonged half-life in the vitreous and can delay or discourage the onset of adverse effects inevitably related to this route of administration. Hence, here we designed MPs composed of a polymeric blend based on poly(lactic-co-glycolic) acid and poloxamers, externally decorated with hyaluronic acid. The MPs are intended for intravitreal administration of bovine serum albumin. In detail, a systematic formulative study aiming to shed light on the complex relationship between protein release rate and MP degradation rate was carried out by means of calorimetric and gel permeation chromatography analyses. We found out that poloxamer addition caused a compact MP matrix, which led to a slight modification of the degradation kinetics and a reduction in the initial BSA initial release, which is of the utmost importance to ensure a relatively regular BSA release. It must also be underlined that for acid-labile molecules such as proteins, the poloxamer’s presence induced complex and hardly predictable effects on MP degradation/protein release, due to the dynamic balance between the time-evolving hydrophilicity of MPs and the influence of poloxamers themselves on the PLGA degradation rate.

scholarly journals Mechanistic Investigations of an α-Aminoarylation Photoredox Reaction

2021 ◽  
Author(s):  
Bernard Stevenson ◽  
Ethan Spielvogel ◽  
Emily Loiaconi ◽  
Victor M. Wambua ◽  
Roman Nakhamiyayev ◽  
...  
Keyword(s):  
Quantum Yield ◽  
Absorption Spectroscopy ◽  
Rate Constant ◽  
Kinetic Modeling ◽  
Rate Constants ◽  
Transient Absorption ◽  
Coupling Reaction ◽  
Time Dependent ◽  
Transient Absorption Spectroscopy ◽  
Mechanistic Investigations

We present time-dependent percent and quantum yield measurements of a photoredox-catalyzed coupling reaction between 1,4-dicyanobenzene and N-phenylpyrrolidine. We also use transient absorption spectroscopy to examine the kinetics within the reaction and use kinetic modeling to extract rate constants and predict how changes in rate constant will impact the quantum yield.

scholarly journals Degradation of Remazol Black dye from Aqueous Solution by Heterogeneous NH3(MoO3)3/H2O2 System

2021 ◽  
pp. 67-78
Author(s):  
Kouakou Yao Urbain ◽  
Kambiré Ollo ◽  
Gnonsoro Urbain Paul ◽  
Eroi N’goran Sévérin ◽  
Trokourey Albert
Keyword(s):  
Hydrogen Peroxide ◽  
Molybdenum Oxide ◽  
Degradation Rate ◽  
Dye Degradation ◽  
Degradation Kinetics ◽  
Sol Gel ◽  
Gel Method ◽  
Sol Gel Method ◽  
Molybdenum Nanoparticles ◽  
Remazol Black

Aims: The pollution of the environment by organic dyes in water is a matter of great concern. Wastewater containing dyes is difficult to treat by conventional wastewater treatment methods such as coagulation, ozonation, biological treatment, etc. This is why the implementation of an effective method by not generating pollutants secondary is necessary. The objective of this work is to study the degradation of remazol black, an azo dye, by the coupling of hydrogen peroxide - molybdenum oxide nanoparticle. The nanoparticles were synthesized by the aqueous sol-gel method using a reflux assembly. Study Design: Random design. Methodology: The nanoparticles were synthesized by the aqueous sol-gel method using a reflux assembly and then characterized by X-ray diffraction and using software origin to determine the particles size by Scherrer's formula. The influence of hydrogen peroxide, molybdenum oxide and hydrogen peroxide / molybdenum oxide coupling, and the degradation kinetics of remazol black were studied. We also studied the influence of the pH of the solution, the mass of molybdenum nanoparticles and the concentration of remazol black on the dye degradation process. Results: The results showed that the synthesized oxide is ammonium molybdenum trioxide NH3(MoO3)3) with a hexagonal structure and size 22.79 nm. The study of the catalytic effect revealed a degradation rate of 17%, 0.83% and 42% respectively for H2O2, NH3(MoO3)3 and the coupling NH3(MoO3)3/H2O2. The study also showed that the degradation of remazol black by the couple NH3(MoO3)3 /H2O2 is better at pH = 4 and for a mass of nanoparticles of 400 mg. This degradation kinetics are pseudo 1st order. In addition, the degradation rate decreases when the concentration of remazol black increases. The efficiency of the coupling (NH3(MoO3)3 / H2O2 showed at ambient temperature, that it was possible to remove about 60% of the initial color of remazol black from the water in a batch reaction. Conclusion: The reflux method makes it possible to synthesize molybdenum nanoparticles. The molybdenum oxide hetero-Fenton process is effective in removing remazol black dye from water.

Sensitivity analysis using a diffuse pollution hydrologic model to assess factors affecting pesticide concentrations in river water

2010 ◽  
Vol 62 (11) ◽  
pp. 2579-2589 ◽  
Author(s):  
Koji Tani ◽  
Yoshihiko Matsui ◽  
Kentaro Narita ◽  
Koichi Ohno ◽  
Taku Matsushita
Keyword(s):  
Sensitivity Analysis ◽  
River Water ◽  
Rate Constant ◽  
Degradation Rate ◽  
Hydrologic Model ◽  
Adsorption Coefficient ◽  
Pesticide Concentration ◽  
Artificial Drainage ◽  
Degradation Rate Constant ◽  
Intermittent Irrigation

We quantitatively evaluated the factors that affect the concentrations of rice-farming pesticides (an herbicide and a fungicide) in river water by a sensitivity analysis using a diffuse pollution hydrologic model. Pesticide degradation and adsorption in paddy soil affected concentrations of the herbicide pretilachlor but did not affect concentrations of the fungicide isoprothiolane. We attributed this difference to the timing of pesticide application in relation to irrigation and drainage of the rice paddy fields. The herbicide was applied more than a month before water drainage of the fields and runoff was gradual over a long period of time, whereas the fungicide was applied shortly before drainage and runoff was rapid. However, the effects of degradability-in-water on the herbicide and fungicide concentrations were similar, with concentrations decreasing only when the rate constant of degradation in water was large. We also evaluated the effects of intermittent irrigation methods (irrigation/artificial drainage or irrigation/percolation) on pesticide concentrations in river water. The runoff of the fungicide, which is applied near or in the period of intermittent irrigation, notably decreased when the method of irrigation/artificial drainage was changed to irrigation/percolation. In a sensitivity analysis evaluating the synergy effect of degradation and adsorbability in soil, the degradation rate constant in soil greatly affected pesticide concentration when the adsorption coefficient was small but did not affect pesticide concentration when the adsorption coefficient was large. The pesticide concentration in the river water substantially decreased when either or both the degradation rate constant in soil and adsorption coefficient was large.

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