scholarly journals Photodegradation of methotrexate in aqueous solution: degradation kinetics and identification of transformation products

2021 ◽  
Author(s):  
Anaïs Espinosa ◽  
Sylvie Nélieu ◽  
Pascale Lieben ◽  
Charles Skarbek ◽  
Raphaël Labruère ◽  
...  
Keyword(s):  
Glutamic Acid ◽  
Environmental Concern ◽  
Degradation Kinetics ◽  
Degradation Mechanism ◽  
Parent Compound ◽  
Drinking Water Treatment ◽  
Transformation Products ◽  
Quantum Yields ◽  
Acid Oxidation ◽  
Ionization State

Abstract Methotrexate is an antineoplastic folate analog of high environmental concern, due to its low biodegradability and toxicological properties. This study focused on its photodegradation under two irradiation conditions, aiming to be representative of environment (300–450 nm) and drinking water treatment (254 nm). The photodegradation experiments were conducted at two pH, to vary the methotrexate ionization state and to produce a large variety of transformation products (TPs). The degradation kinetics determined through LC-UV monitoring were contrasted according to pH and irradiation wavelength. However, the quantum yields were independent of ionization state at 254 nm and the changes in kinetics at higher wavelengths were attributed to a change in the degradation mechanism. The TPs formed during the reactions were identified by UHPLC-MS/MS, using both the positive and negative modes. Among the eleven proposed structures, five were described as methotrexate TPs for the first time. The TPs result from N-demethylation, glutamic acid oxidation and C-N cleavage, all of them leading to further degraded photoproducts presenting modified or lost glutamic acid part. This was made possible thanks to the negative mode, which allowed the exploration of the glutamic acid moiety modifications. Cytotoxicity assessment on A549 cancer cells demonstrated that all photoproducts formed at pH 7 were less toxic than the parent compound.

Thermal degradation kinetics of Opuntia Ficus Indica flour and talc-filled poly (lactic acid) hybrid biocomposites by TGA analysis

2021 ◽  
pp. 002199832110082
Author(s):  
Azzeddine Gharsallah ◽  
Abdelheq Layachi ◽  
Ali Louaer ◽  
Hamid Satha
Keyword(s):  
Thermal Stability ◽  
Lactic Acid ◽  
Thermal Degradation ◽  
Degradation Kinetics ◽  
Degradation Mechanism ◽  
Melt Processing ◽  
Thermal Degradation Kinetics ◽  
Poly Lactic Acid ◽  
Opuntia Ficus Indica ◽  
Model Free

This paper reports the effect of lignocellulosic flour and talc powder on the thermal degradation behavior of poly (lactic acid) (PLA) by thermogravimetric analysis (TGA). Lignocellulosic flour was obtained by grinding Opuntia Ficus Indica cladodes. PLA/talc/ Opuntia Ficus Indica flour (OFI-F) biocomposites were prepared by melt processing and characterized using Wide-angle X-ray scattering (WAXS) and Scanning Electron Microscope (SEM). The thermal degradation of neat PLA and its biocomposites can be identified quantitatively by solid-state kinetics models. Thermal degradation results on biocomposites compared to neat PLA show that talc particles at 10 wt % into the PLA matrix have a minor impact on the thermal stability of biocomposites. Loading OFI-F and Talc/OFI-F mixture into the PLA matrix results in a decrease in the maximum degradation temperature, which means that the biocomposites have lower thermal stability. The activation energies (Ea) calculated by the Flynn Wall Ozawa (FWO) and Kissinger Akahira Sunose (KAS) model-free approaches and by model-fitting (Kissinger method and Coats-Redfern method) are in good agreement with one another. In addition, in this work, the degradation mechanism of biocomposites is proposed using Coats-Redfern and Criado methods.

scholarly journals Omnipresent distribution of herbicides and their transformation products in all water body types of an agricultural landscape in the North German Lowland

2021 ◽  
Author(s):  
Uta Ulrich ◽  
Matthias Pfannerstill ◽  
Guido Ostendorp ◽  
Nicola Fohrer
Keyword(s):  
Drinking Water ◽  
Oxalic Acid ◽  
Water Body ◽  
Sulfonic Acid ◽  
Stream Water ◽  
Parent Compound ◽  
Shallow Groundwater ◽  
Transformation Products ◽  
Small Scale ◽  
Rainfall Events

AbstractThe research of the environmental fate of pesticides has demonstrated that applied compounds are altered in their molecular structure over time and are distributed within the environment. To assess the risk for contamination by transformation products (TP) of the herbicides flufenacet and metazachlor, the following four water body types were sampled in a small-scale catchment of 50 km2 in 2015/2016: tile drainage water, stream water, shallow groundwater, and drinking water of private wells. The TP were omnipresent in every type of water body, more frequently and in concentrations up to 10 times higher than their parent compounds. Especially metazachlor sulfonic acid, metazachlor oxalic acid, and flufenacet oxalic acid were detected in almost every drainage and stream sample. The transformation process leads to more mobile and more persistent molecules resulting in higher detection frequencies and concentrations, which can even occur a year or more after the application of the parent compound. The vulnerability of shallow groundwater and private drinking water wells to leaching compounds is proved by numerous positives of metazachlor-TP with maximum concentrations of 0.7 μg L−1 (drinking water) and 20 μg L−1 (shallow groundwater) of metazachlor sulfonic acid. Rainfall events during the application period cause high discharge of the parent compound and lower release of TP. Later rainfall events lead to high displacement of TP. For an integrated risk assessment of water bodies, the environmental behavior of pesticide-TP has to be included into regular state-of-the-art water quality monitoring.

scholarly journals Carbaryl Photochemical Degradation on Soil Model Surfaces

Soil Systems ◽  
2019 ◽  
Vol 3 (1) ◽  
pp. 17 ◽  
Author(s):  
Marie Siampiringue ◽  
Rajae Chahboune ◽  
Pascal Wong-Wah-Chung ◽  
Mohamed Sarakha
Keyword(s):  
Liquid Chromatography ◽  
Light Exposure ◽  
Degradation Mechanism ◽  
Parent Compound ◽  
Toxicity Tests ◽  
Photochemical Degradation ◽  
First Order Kinetics ◽  
A Value ◽  
Order Of Magnitude ◽  
Set Up

The phototransformation of carbaryl was investigated upon solar light exposure on three surfaces, silica, kaolin and sand, as soil models. By excitation with a Suntest set up at the surface of the three solid supports, the degradation of carbaryl followed first-order kinetics with a rate constant of 0.10 h−1. By using the Kubelka Munk model, the quantum yield disappearance at the surface of kaolin was evaluated to 2.4 × 10−3. Such a value is roughly one order of magnitude higher than that obtained in aqueous solutions. The results indicated that the particle size and the specific surface area of the various models have significant effects. The photo-oxidative properties as well as the byproduct elucidation by liquid chromatography combined with diode arrays (LC-DAD) and liquid chromatography coupled mass spectrometry (LC-MS) analyses allowed us to propose the degradation mechanism pathways. The main products were 1-naphtol and 2-hydroxy-1,4-naphthoquinone, which arise from a photo-oxidation process together with products from photo-Fries, photo-ejection and methyl carbamate hydrolysis. The toxicity tests clearly showed a significant decrease of the toxicity in the early stages of the irradiation. This clearly shows that the generated products are less toxic than the parent compound.

scholarly journals Cometabolism of Trihalomethanes by Nitrosomonas europaea

2005 ◽  
Vol 71 (12) ◽  
pp. 7980-7986 ◽  
Author(s):  
David G. Wahman ◽  
Lynn E. Katz ◽  
Gerald E. Speitel
Keyword(s):  
Drinking Water ◽  
Rate Constants ◽  
Degradation Kinetics ◽  
Drinking Water Treatment ◽  
Nitrosomonas Europaea ◽  
Ammonia Nitrogen ◽  
Degradation Rates ◽  
Ammonia Oxidizing Bacterium ◽  
Treated Drinking Water ◽  
Bromine Substitution

ABSTRACT The ammonia-oxidizing bacterium Nitrosomonas europaea (ATCC 19718) was shown to degrade low concentrations (50 to 800 μg/liter) of the four trihalomethanes (trichloromethane [TCM], or chloroform; bromodichloromethane [BDCM]; dibromochloromethane [DBCM]; and tribromomethane [TBM], or bromoform) commonly found in treated drinking water. Individual trihalomethane (THM) rate constants ( \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(k_{1_{THM}}\) \end{document} ) increased with increasing THM bromine substitution, with TBM > DBCM > BDCM > TCM (0.23, 0.20, 0.15, and 0.10 liters/mg/day, respectively). Degradation kinetics were best described by a reductant model that accounted for two limiting reactants, THMs and ammonia-nitrogen (NH3-N). A decrease in the temperature resulted in a decrease in both ammonia and THM degradation rates with ammonia rates affected to a greater extent than THM degradation rates. Similarly to the THM degradation rates, product toxicity, measured by transformation capacity (Tc ), increased with increasing THM bromine substitution. Because both the rate constants and product toxicities increase with increasing THM bromine substitution, a water's THM speciation will be an important consideration for process implementation during drinking water treatment. Even though a given water sample may be kinetically favored based on THM speciation, the resulting THM product toxicity may not allow stable treatment process performance.

scholarly journals Optimization Parameters, Kinetics and Mechanism of Naproxen Removal by Catalytic Wet Peroxide Oxidation with a Hybrid Iron-Based Magnetic Catalyst

Catalysts ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 287 ◽  
Author(s):  
Ysabel Huaccallo-Aguilar ◽  
Silvia Álvarez-Torrellas ◽  
Marcos Larriba ◽  
V. Ismael Águeda ◽  
José Antonio Delgado ◽  
...  
Keyword(s):  
Degradation Kinetics ◽  
Degradation Mechanism ◽  
Treatment Plant ◽  
Operating Conditions ◽  
Surface Model ◽  
Oh Radicals ◽  
Order Kinetic ◽  
Peroxide Oxidation ◽  
Wet Peroxide Oxidation ◽  
Catalytic Wet Peroxide Oxidation

This work presents a study of the assessment of the operating parameters of the catalytic wet peroxide oxidation (CWPO) of naproxen (NAP) using magnetite/multi-walled carbon nanotubes (Fe3O4/MWCNTs) as a catalyst. The effect of pH, temperature, and H2O2 dosage on CWPO process was evaluated by using the response surface model (RSM), allowing us to obtain an optimum NAP removal of 82% at the following operating conditions: pH = 5, T = 70 °C, [H2O2]0 = 1.5 mM, and [NAP]0 = 10.0 mg/L. Therefore, NAP degradation kinetics were revealed to follow a pseudo-second-order kinetic model, and an activation energy value of 4.75 kJ/mol was determined. Adsorption and using only H2O2 experiments, both considered as blank tests, showed no significant removal of the pollutant. Moreover, Fe3O4/MWCNTs material exhibited good recyclability along three consecutive cycles, finding an average NAP removal percentage close to 80% in each cycle of 3 h reaction time. In addition, the scavenging tests confirmed that the degradation of NAP was mainly governed by •OH radicals attack. Two reaction sequences were proposed for the degradation mechanism according to the detected byproducts. Finally, the versatility of the catalyst was evidenced in the treatment of different environmentally relevant aqueous matrices (wastewater treatment plant effluent (WWTP), surface water (SW), and a hospital wastewater (HW)) spiked with NAP, obtaining total organic carbon (TOC) removal efficiencies after 8 h in the following order: NAP-SW > NAP-HW > NAP-WWTP.

scholarly journals Ibuprofen Degradation and Associated Bacterial Communities in Hyporheic Zone Sediments

2020 ◽  
Vol 8 (8) ◽  
pp. 1245
Author(s):  
Cyrus Rutere ◽  
Kirsten Knoop ◽  
Malte Posselt ◽  
Adrian Ho ◽  
Marcus A. Horn
Keyword(s):  
Microbial Community ◽  
16S Rrna ◽  
Hyporheic Zone ◽  
Community Dynamics ◽  
Environmental Concern ◽  
Transformation Products ◽  
Pollutant Removal ◽  
Pcr Analysis ◽  
Rrna Gene ◽  
Microbial Community Dynamics

Ibuprofen, a non-steroidal anti-inflammatory pain reliever, is among pharmaceutical residues of environmental concern ubiquitously detected in wastewater effluents and receiving rivers. Thus, ibuprofen removal potentials and associated bacteria in the hyporheic zone sediments of an impacted river were investigated. Microbially mediated ibuprofen degradation was determined in oxic sediment microcosms amended with ibuprofen (5, 40, 200, and 400 µM), or ibuprofen and acetate, relative to an un-amended control. Ibuprofen was removed by the original sediment microbial community as well as in ibuprofen-enrichments obtained by re-feeding of ibuprofen. Here, 1-, 2-, 3-hydroxy- and carboxy-ibuprofen were the primary transformation products. Quantitative real-time PCR analysis revealed a significantly higher 16S rRNA abundance in ibuprofen-amended relative to un-amended incubations. Time-resolved microbial community dynamics evaluated by 16S rRNA gene and 16S rRNA analyses revealed many new ibuprofen responsive taxa of the Acidobacteria, Actinobacteria, Bacteroidetes, Gemmatimonadetes, Latescibacteria, and Proteobacteria. Two ibuprofen-degrading strains belonging to the genera Novosphingobium and Pseudomonas were isolated from the ibuprofen-enriched sediments, consuming 400 and 300 µM ibuprofen within three and eight days, respectively. The collective results indicated that the hyporheic zone sediments sustain an efficient biotic (micro-)pollutant degradation potential, and hitherto unknown microbial diversity associated with such (micro)pollutant removal.

Photocatalytic removal of taste and odour compounds for drinking water treatment

2009 ◽  
Vol 9 (5) ◽  
pp. 477-483 ◽  
Author(s):  
H. Tran ◽  
G. M. Evans ◽  
Y. Yan ◽  
A. V. Nguyen
Keyword(s):  
Drinking Water ◽  
Sodium Bicarbonate ◽  
Photocatalytic Degradation ◽  
Rate Constants ◽  
Degradation Rate ◽  
Degradation Mechanism ◽  
Drinking Water Treatment ◽  
Degradation Process ◽  
Negative Effects ◽  
Reaction Rate Constants

Photocatalytic degradation of geosmin and 2-methylisoborneol (MIB), which are two taste and odour compounds commonly found in drinking water supply sources, was investigated using an immobilised TiO2 photoreactor. It was found that the degradation of geosmin and MIB followed similar pseudo-first-order kinetics with reaction rate constants being approximately 0.025 min−1 for typical geosmin and MIB concentrations of 250 and 500 ng/L. The normalised formal quantum efficiency was calculated to be in the range of 162–182 L/mol. Influence of additives (i.e. sodium bicarbonate and alcohols) on the degradation process was also investigated. It was found that there was a small reduction in the degradation rate constants of geosmin and MIB with increasing sodium bicarbonate concentration. At 50 mg/L sodium bicarbonate the degradation rate constants decreased by approximately 5%. Similarly, for methanol and ethanol concentrations up to 35 and 50 mg/L, respectively, these constants were found to also decrease. While addition of sodium bicarbonate and alcohols was seen to have relatively small negative effects on the photocatalytic degradation performance, the magnitude of their influence was consistent with the hypothesis that the degradation mechanism of geosmin and MIB was predominately that of attack involving HO∙ radicals.

scholarly journals Study on the degradation mechanism and pathway of benzene dye intermediate 4-methoxy-2-nitroaniline via multiple methods in Fenton oxidation process

RSC Advances ◽  
2018 ◽  
Vol 8 (20) ◽  
pp. 10764-10775 ◽  
Author(s):  
Ying Guo ◽  
Qiang Xue ◽  
Kangping Cui ◽  
Jia Zhang ◽  
Hui Wang ◽  
...  
Keyword(s):  
Oxidation Process ◽  
Environmental Concern ◽  
Degradation Mechanism ◽  
Fenton Oxidation ◽  
Multiple Methods ◽  
Carcinogenic Effects ◽  
Fenton Oxidation Process

Benzene dye intermediate (BDI) 4-methoxy-2-nitroaniline (4M2NA) wastewater has caused significant environmental concern due to its strong toxicity and potential carcinogenic effects.

Synthesis and photophysicochemical studies of non-metal 2,3,9,10,16,17,23,24-octacarboxyphthalocyanine

2012 ◽  
Vol 16 (12) ◽  
pp. 1244-1251 ◽  
Author(s):  
Nina A. Kuznetsova ◽  
Ekaterina N. Shevchenko ◽  
Dmitry A. Makarov ◽  
Ludmila K. Slivka ◽  
Ludmila I. Solovyova ◽  
...  
Keyword(s):  
Singlet Oxygen ◽  
New Method ◽  
Quantum Yields ◽  
Ionization State

A new method of preparation and the properties (solubility, aggregation, spectralluminescent properties, singlet oxygen and photobleaching quantum yields) of non-metal 2,3,9,10,16,17,23,24-octacarboxyphthalocyanine are reported. The influence of ionization state on photophysicochemical properties of this dye is also presented.

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