Ozonation of ofloxacin in water: By-products, degradation pathway and ecotoxicity assessment

The chlorination of dissolved amino acids can generate disinfection by-products (DBPs). To prevent the formation of DBPs, we examined the UV-induced degradation of tryptophan (Trp). In order to further understand the impact of UV disinfection on Trp, the effects of initial concentrations of Trp, pH, temperature, concentrations of NO3−, HCO3− and Cl− on Trp removal were investigated, and a degradation mechanism was also proposed. The results demonstrated that degradation fitted a pseudo first-order reaction kinetic model. The degradation of Trp was mainly caused by direct UV degradation. The apparent rate constant kobs decreased with the increase in initial Trp concentration and increased with increases in pH and temperature. The thermal degradation activation energy was 19.65 kJ/mol. Anions in water also had a significant influence on the degradation of Trp. HCO3− and NO3− contributed to the kobs of Trp, but Cl− inhibited the degradation rate. By electron paramagnetic resonance (EPR) spectroscopy, ·OH was proven to be formed during the degradation of Trp by UV. Based on the intermediate products of C11H15NO3, C10H15N and C9H13N detected by LC-MS-MS, the degradation pathway of Trp was speculated.

Download Full-text

Electrochemical Degradation of Metoprolol Using Graphite-PVC Composite as Anode: Elucidation and Characterization of New by-products Using LC-TOF/MS

Journal of the Mexican Chemical Society ◽

10.29356/jmcs.v64i3.1139 ◽

2020 ◽

Vol 64 (3) ◽

Author(s):

Fouad Fadhil Al-Qaim ◽

Zainab Haider Mussa ◽

Ali Yuzir ◽

Kamyar Shameli

Keyword(s):

Degradation Pathway ◽

Strong Electrolyte ◽

Electrochemical Degradation ◽

Kinetic Rate Constant ◽

Flight Mass Spectrometry ◽

Nacl Concentration ◽

Insuficiencia Cardiaca ◽

Consumption Energy ◽

Wastewater Samples ◽

By Products

Abstract. Metoprolol (MTP) is one of pharmaceuticals used for treatment of heart failure and hypertension. It was frequently detected in wastewater samples either influent or effluent. The application of graphite-PVC composite as anode was investigated for the degradation of metoprolol in the presence of strong electrolyte such as sodium chloride (NaCl). The degradation rate was strongly influenced by initial concentrations of metoprolol, NaCl concentration and applied voltage. An initial concentration of 2 mg/L was eliminated more than 95% after 30 min under optimum conditions; 5000 mg/L NaCl and 5 V. The consumption energy of the electrochemical reaction was 0.665 Wh/mg for metoprolol after 30 min. The kinetic rate constant of metoprolol could be ranged between 0.0016 and 0.0801 min-1. The electrochemical degradation efficiency of metoprolol and its by-products has been achieved. The degradation of metoprolol produced four transformated products as investigated and elucidated using liquid chromatography-time of flight/mass spectrometry. The proposed degradation pathway of metoprolol was schemed on the base of the identified intermediates. Resumen. El metoprolol (MTP) es uno de los fármacos utilizados para el tratamiento de la insuficiencia cardíaca y la hipertensión. Se detecta frecuentemente en muestras de aguas residuales, ya sea de afluentes o efluentes. Se investigó la aplicación del compuesto de grafito-PVC como ánodo para la degradación del metoprolol en presencia de un electrolito fuerte como el cloruro de sodio (NaCl). La velocidad de degradación depende de las concentraciones iniciales de metoprolol, la concentración de NaCl y el voltaje aplicado. Una concentración inicial de 2 mg/L de MTP fue eliminada con más del 95% después de 30 minutos en condiciones óptimas; 5000 mg/L de NaCl y 5 V. La energía de consumo de la reacción electroquímica fue de 0,665 Wh/mg para el metoprolol después de 30 min. La constante cinética de degradación metoprolol oscila entre 0.0016 y 0.0801 min-1. Se logró la eficiente degradación electroquímica del metoprolol y sus subproductos, ya que se detectaron cuatro subproductos electrogenerados según los resultados de cromatografía líquida - tiempo de vuelo/espectrometría de masas. La vía de degradación propuesta del metoprolol se esquematizó sobre la base de los productos intermedios identificados.

Download Full-text

Aqueous photodegradation of 4-tert-butylphenol: By-products, degradation pathway and theoretical calculation assessment

The Science of The Total Environment ◽

10.1016/j.scitotenv.2016.05.064 ◽

2016 ◽

Vol 566-567 ◽

pp. 86-92 ◽

Cited By ~ 6

Author(s):

Yanlin Wu ◽

Jin Shi ◽

Hongche Chen ◽

Jianfu Zhao ◽

Wenbo Dong

Keyword(s):

Theoretical Calculation ◽

Degradation Pathway ◽

By Products

Download Full-text

Oxidative degradation of sulfamethoxazole from secondary treated effluent by ferrate(VI): kinetics, by-products, degradation pathway and toxicity assessment

Journal of Environmental Health Science and Engineering ◽

10.1007/s40201-021-00769-9 ◽

2022 ◽

Author(s):

Behjat Jebalbarezi ◽

Reza Dehghanzadeh ◽

Samira Sheikhi ◽

Najmeh Shahmahdi ◽

Hassan Aslani ◽

...

Keyword(s):

Oxidative Degradation ◽

Degradation Pathway ◽

Toxicity Assessment ◽

Treated Effluent ◽

By Products

Download Full-text

Hydrogen Cyanide Polymers from the Impact of Comet P/Shoemaker-Levy 9 on Jupiter

International Astronomical Union Colloquium ◽

10.1017/s025292110001469x ◽

1997 ◽

Vol 161 ◽

pp. 179-187

Author(s):

Clifford N. Matthews ◽

Rose A. Pesce-Rodriguez ◽

Shirley A. Liebman

Keyword(s):

Amino Acids ◽

Solar System ◽

Hydrogen Cyanide ◽

Nitrogen Heterocycles ◽

Laboratory Studies ◽

Heterogeneous Solids ◽

The Many ◽

Comet Halley ◽

The Impact ◽

By Products

AbstractHydrogen cyanide polymers – heterogeneous solids ranging in color from yellow to orange to brown to black – may be among the organic macromolecules most readily formed within the Solar System. The non-volatile black crust of comet Halley, for example, as well as the extensive orangebrown streaks in the atmosphere of Jupiter, might consist largely of such polymers synthesized from HCN formed by photolysis of methane and ammonia, the color observed depending on the concentration of HCN involved. Laboratory studies of these ubiquitous compounds point to the presence of polyamidine structures synthesized directly from hydrogen cyanide. These would be converted by water to polypeptides which can be further hydrolyzed to α-amino acids. Black polymers and multimers with conjugated ladder structures derived from HCN could also be formed and might well be the source of the many nitrogen heterocycles, adenine included, observed after pyrolysis. The dark brown color arising from the impacts of comet P/Shoemaker-Levy 9 on Jupiter might therefore be mainly caused by the presence of HCN polymers, whether originally present, deposited by the impactor or synthesized directly from HCN. Spectroscopic detection of these predicted macromolecules and their hydrolytic and pyrolytic by-products would strengthen significantly the hypothesis that cyanide polymerization is a preferred pathway for prebiotic and extraterrestrial chemistry.

Download Full-text