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

2017 ◽  
Vol 75 (9) ◽  
pp. 2163-2170 ◽  
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.

The effect of photosensitizer on diclofenac photodegradation under simulated sunlight

2013 ◽  
Vol 67 (2) ◽  
pp. 418-423 ◽  
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.

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

2021 ◽  
Vol 02 ◽  
Author(s):  
Emmanuel M. de la Fournière ◽  
Jorge M. Meichtry ◽  
Graciela S. Custo ◽  
Eduardo A. Gautier ◽  
Marta I. Litter
Keyword(s):  
Degradation Products ◽  
Acidic Ph ◽  
Cosmetic Products ◽  
Acid Product ◽  
First Order ◽  
First Order Kinetics ◽  
Photocatalytic Destruction ◽  
Pseudo First Order ◽  
Mineralization Degree ◽  
Suitable Technique

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.

scholarly journals Efficient degradation of naproxen by persulfate activated with zero-valent iron: performance, kinetic and degradation pathways

2020 ◽  
Vol 81 (10) ◽  
pp. 2078-2091
Author(s):  
Shuyu Dong ◽  
Xiaoxue Zhai ◽  
Ruobing Pi ◽  
Jinbao Wei ◽  
Yunpeng Wang ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Hydroxyl Radical ◽  
Rate Constants ◽  
Zero Valent Iron ◽  
Degradation Pathways ◽  
First Order ◽  
First Order Kinetics ◽  
Degradation Rates ◽  
Initial Ph ◽  
Pseudo First Order

Abstract Degradation of naproxen (NAP) by persulfate (PS) activated with zero-valent iron (ZVI) was investigated in our study. The NAP in aqueous solution was degraded effectively by the ZVI/PS system and the degradation exhibited a pseudo-first-order kinetics pattern. Both sulfate radical (SO4•−) and hydroxyl radical (HO•) participate in the NAP degradation. The second-order rate constants for NAP reacting with SO4•− and HO• were (5.64 ± 0.73) × 109 M−1 s−1 and (9.05 ± 0.51) × 109 M−1 s−1, respectively. Influence of key parameters (initial pH, PS dosage, ZVI dosage, and NAP dosage) on NAP degradation were evaluated systematically. Based on the detected intermediates, the pathways of NAP degradation in ZVI/PS system was proposed. It was found that the presence of ammonia accelerated the corrosion of ZVI and thus promoted the release of Fe2+, which induced the increased generation of sulfate radicals from PS and promoted the degradation of NAP. Compared to its counterpart without ammonia, the degradation rates of NAP by ZVI/PS were increased to 3.6–17.5 folds and 1.2–2.2 folds under pH 7 and pH 9, respectively.

scholarly journals Photodegradation of lincomycin in aqueous solution

2006 ◽  
Vol 2006 ◽  
pp. 1-6 ◽  
Author(s):  
Agatino Di Paola ◽  
Maurizio Addamo ◽  
Vincenzo Augugliaro ◽  
Elisa García-López ◽  
Vittorio Loddo ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Aqueous Solutions ◽  
Uv Light ◽  
Heterogeneous Systems ◽  
Degradation Pathways ◽  
Direct Photolysis ◽  
First Order ◽  
First Order Kinetics ◽  
Pseudo First Order ◽  
Complete Mineralization

Aqueous solutions of lincomycin were irradiated with UV light in homogeneous and heterogeneous systems. Lincomycin disappeared in both systems but the presence ofTiO2noticeably accelerated the degradation of the antibiotic in comparison with direct photolysis. The rate of decomposition was dependent on the concentration of lincomycin and followed a pseudo-first-order kinetics. Photolysis involved only the oxidation of lincomycin without mineralization. Differently, the treatment withTiO2and UV light resulted in a complete mineralization of the antibiotic. The degradation pathways involved S- and N-demethylation and propyldealkylation. The mineralization of the molecule led to the formation of sulfate, ammonium, and nitrate ions.

scholarly journals ESTUDO DE ESTABILIDADE DO FOSFATO DISSÓDICO DE PREDNISOLONA EM CONDIÇÕES DE ESTRESSE OXIDATIVO E TÉRMICO, EM FORMULAÇÃO ORAL

2018 ◽  
Vol 35 (4) ◽  
pp. 09
Author(s):  
Cleber Antonio Lindino ◽  
Marcia Lina Mitsui ◽  
Rodolfo Ortiguara ◽  
Daiane Felin ◽  
Mauricio Ferreira Da Rosa ◽  
...  
Keyword(s):  
High Performance ◽  
Dosage Form ◽  
Degradation Products ◽  
Degradation Process ◽  
Oral Solution ◽  
Form Solution ◽  
Oral Dosage ◽  
First Order ◽  
First Order Kinetics

This work was to investigate the process of degradation of the drug Prednisolone Sodium Phosphate (FSP) in oral solution dosage form through the degradation experiments, evaluating the parameters in accordance with Resolution 899/2003 ANVISA and the degradation process of the drug. The method by high performance liquid chromatography (HPLC) developed for the determination of the drug was validated to demonstrate its applicability as an indicator of stability, ensuring reliability. After the method be validated to study the degradation of the drug, it was shown that drastic conditions of oxidative stress (H O 30%) and 2 2 temperature 60°C, the degradation of the drug is dependent on its concentration (first order kinetics). The results were  satisfactory, showing that this method is suitable to investigate the formation of degradation products in oral dosage form solution

scholarly journals Hydrolysis and Photolysis Kinetics, and Identification of Degradation Products of the Novel Bactericide 2-(4-Fluorobenzyl)-5-(Methylsulfonyl)-1,3,4-Oxadiazole in Water

2018 ◽  
Vol 15 (12) ◽  
pp. 2741 ◽  
Author(s):  
Xingang Meng ◽  
Lingzhu Chen ◽  
Yuping Zhang ◽  
Deyu Hu ◽  
Baoan Song
Keyword(s):  
Degradation Product ◽  
High Performance ◽  
Degradation Products ◽  
Degradation Mechanism ◽  
The Novel ◽  
Initial Concentration ◽  
First Order ◽  
First Order Kinetics ◽  
Kinetics Of ◽  
High Resolution Mass Spectrometer

Hydrolysis and photolysis kinetics of Fubianezuofeng (FBEZF) in water were investigated in detail. The hydrolysis half-lives of FBEZF depending on pH, initial concentration, and temperature were (14.44 d at pH = 5; 1.60 d at pH = 7), (36.48 h at 1.0 mg L−1; 38.51 h at 5.0 mg L−1; and 31.51 h at 10.0 mg L−1), and (77.02 h at 15 °C; 38.51 h at 25 °C; 19.80 h at 35 °C; and 3.00 h at 45 °C), respectively. The photolysis half-life of FBEZF in different initial concentrations were 8.77 h at 1.0 mg L−1, 8.35 h at 5.0 mg L−1, and 8.66 h at 10.0 mg L−1, respectively. Results indicated that the degradation of FBEZF followed first-order kinetics, as the initial concentration of FBEZF only had a slight effect on the UV irradiation effects, and the increase in pH and temperature can substantially accelerate the degradation. The hydrolysis Ea of FBEZF was 49.90 kJ mol−1, which indicates that FBEZF belongs to medium hydrolysis. In addition, the degradation products were identified using ultra-high-performance liquid chromatography coupled with an Orbitrap high-resolution mass spectrometer. One degradation product was extracted and further analyzed by 1H-NMR, 13C-NMR, 19F-NMR, and MS. The degradation product was identified as 2-(4-fluorobenazyl)-5-methoxy-1,3,4-oxadiazole, therefore a degradation mechanism of FBEZF in water was proposed. The research on FBEZF can be helpful for its safety assessment and increase the understanding of FBEZF in water environments.

Exploitation of Ag3PO4 Impregnated Alginate Beads for the Photocatalytic Degradation of Dye Solution under Sunlight Irradiation

2017 ◽  
Vol 751 ◽  
pp. 689-694
Author(s):  
Katnanipa Wanchai
Keyword(s):  
Methylene Blue ◽  
High Performance ◽  
Alginate Beads ◽  
Precipitation Method ◽  
Order Model ◽  
Sunlight Irradiation ◽  
First Order ◽  
Ft Ir ◽  
Pseudo First Order ◽  
Photocatalytic Reactions

Ag3PO4-alginate beads (AAB) were synthesized by simple precipitation method and their structure was characterized by XRD, FT-IR and SEM/EDS, respectively. The AAB was evaluated as the photocatalyst for degradation of methylene blue (MB) under sunlight irradiation. The results showed that AAB exhibited the high performance for degradation of MB (97.6%) in 60 min. The kinetic studied demonstrated that the photocatalytic reactions followed the pseudo first-order model. Moreover, AAB can maintain full photodegradation activity for at least five cycles. Consequently, the AAB are promising materials for the photocatalytic of dyes or similar organic contaminant in environmental pollution cleanup.

Decolourization of Alizarin Red by Persulfate

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.

Remarkable Sunlight Photocatalytic Activity due to Synergetic Effect of ZnO with Cu

2017 ◽  
Vol 727 ◽  
pp. 388-394 ◽  
Author(s):  
Wei Liang Wang ◽  
Chuan Xi Yang ◽  
Feng Zhang ◽  
Ping Li ◽  
Guan Wei Cui
Keyword(s):  
Aqueous Solution ◽  
Photocatalytic Activity ◽  
Synergetic Effect ◽  
Weight Ratio ◽  
Heterogeneous Photocatalysis ◽  
Zno Nanorod ◽  
Sunlight Irradiation ◽  
First Order ◽  
First Order Kinetics ◽  
Pseudo First Order

The ZnO nanorod was synthesized by the hydrothermal method, and Cu/ZnO nanorod was synthesized by modifying the prepared ZnO nanorod. The TEM was used to characterize the morphology and microstructure for ZnO and Cu/ZnO nanorod. The length of nanorod ZnO was about 700-800 nm, and the diameter about 40-50 nm. There was no change of ZnO in length and diameter when doped with Cu. The degradation of methylene blue (MB) in an aqueous solution under sunlight irradiation was carried out to evaluate the photocatalytic activity. The Cu/ZnO nanorod shows significantly higher photocatalytic activity (99.91%) than ZnO nanorod (89.66%) under sunlight irradiation. The degradation of MB accords with pseudo-first order kinetics, and the appear rate constants kapp of 7% Cu/ZnO nanorod was about 3 times higher than ZnO nanorod. The synergetic effect between ZnO nanorod and Cu on the photocatalytic degradation of MB exists clearly for all the nanorods, and the optimum synergetic effect was found at a weight ratio of 7 wt % (Cu/ZnO). It hoped our works could provide valuable information on the synthesis and application of ZnO-based heterogeneous photocatalysis.

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

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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