RESUMEN
In this study, the electrochemical degradation process of 5-fluorouracil (5-FU) in aqueous media was performed using a continuous flow reactor in an undivided cell (system I), and in a divided cell with a cationic membrane (Nafion® 424) (system II). In system I, 75% of 5-FU degradation was achieved (50â¯mgâ¯L-1) with a applied current density jappâ¯=â¯150 A m-2, volumetric flow rate qvâ¯=â¯13â¯Lâ¯h-1, after 6â¯h of electrolysis (kappâ¯=â¯0.004 min-1). The removal efficiency of 5-FU was higher (95%) when the concentration was 5â¯mgâ¯L-1 under the same conditions. Nitrates (22% of initial amount of N), fluorides (27%) and ammonium (10%) were quantified after 6â¯h of electrolysis. System II, 77% of 5-FU degradation was achieved (50â¯mgâ¯L-1) after 6â¯h of electrolysis (kappâ¯=â¯0.004 min-1). The degradation rate of 5-FU was complete when the concentration was 5â¯mgâ¯L-1 under the same conditions. Nitrates (29% of initial amount of N), fluorides (25%) and ammonium (5%) were quantified after 6â¯h of electrolysis. In addition, the main organic byproducts identified by mass spectroscopy were aliphatic compound with carbonyl and carboxyl functionalities. Due to, the mineralization of 5-FU with acceptable efficiency of 88% found in system II (japp of 200 A m-2), this system seems to be more promising in the cytostatic drug removal. Moreover the efficiency of 5-FU removal in diluted solutions is better in system II than in system I.
Asunto(s)
Boro/química , Diamante/química , Electrólisis/métodos , Fluorouracilo/análisis , Contaminantes Químicos del Agua/análisis , Purificación del Agua/métodos , Electrodos , Electrólisis/instrumentación , Fluorouracilo/química , Cinética , Oxidación-Reducción , Contaminantes Químicos del Agua/química , Purificación del Agua/instrumentaciónRESUMEN
The O-polysaccharide of Salmonella Telaviv was obtained by mild acid degradation of the lipopolysaccharide and studied by chemical methods (sugar and methylation analyses, Smith degradation, de-O-acetylation) and NMR spectroscopy. The structure of the O-polysaccharide was established. The repeating units that are proximal to the lipopolysaccharide core region mostly have a digalactose side chain and lack glucose, whereas those at the other end of the chain mostly do bear glucose but are devoid of the disaccharide side chain. This is the first structure established for the O-polysaccharide of a Salmonella serogroup O:28 (formerly M) strain characterized by subfactors O28(1) and O28(2). Knowledge of this structure and the structure of the O-polysaccharide of Salmonella Dakar (O28(1), O28(3)) established earlier is crucial for determination of the exact structures associated with subfactors O28(1), O28(2), and O28(3) and elucidation of the genetic basis of the close relationship between Escherichia coli O71 and S. enterica O:28 O-antigens.
Asunto(s)
Antígenos O/química , Salmonella enterica/química , Acetilglucosamina/análogos & derivados , Acetilglucosamina/análisis , Secuencia de Carbohidratos , Datos de Secuencia Molecular , Resonancia Magnética Nuclear Biomolecular , Salmonella enterica/inmunologíaRESUMEN
Commonly used alkylimidazolium ionic liquids are poorly to negligibly biodegradable, and some are toxic, with the potential to poison typical biological test systems. Therefore, when ionic liquids are present in technological wastewaters they could break through classical wastewater treatment systems into natural waters and become potentially persistent pollutants. A recent study investigating different advanced oxidation processes found that the H(2)O(2)/UV system degraded dissolved imidazolium ionic liquids with the greatest efficiency. In the present study, high performance liquid chromatography was coupled with electrospray mass spectrometry to separate, analyse and identify degradation products following the treatment of ionic liquid solutions with H(2)O(2) in the presence of UV irradiation. It was found that hydroxylation in short-chain entities occurred mainly within the ring moiety, whereas in the case of longer alkylated cations, oxidation of the alkyl chain yielded several products. The potential transformation products were identified structurally by MS/MS analysis and are discussed in the light of their putative toxicity and biodegradability.
Asunto(s)
Líquidos Iónicos , Iones , Oxígeno/química , Contaminantes Químicos del Agua/análisis , Purificación del Agua/métodos , Biodegradación Ambiental , Peróxido de Hidrógeno/química , Luz , Fotoquímica/métodos , Espectrometría de Masa por Ionización de Electrospray/métodos , Espectrometría de Masas en Tándem/métodos , Rayos Ultravioleta , Eliminación de Residuos Líquidos/métodosRESUMEN
Ionic liquids are widely studied as alternative solvents in organic synthesis and catalysis, in electrochemistry and the separation sciences; with their many applications they will soon be produced on an industrial scale. Available toxicological data of ionic liquids have already suggested initial guidelines for the conscious design of safer chemicals. In this study a new group of such redesigned ionic liquids-1-alkoxymethyl-3-hydroxypyridinium cations+acesulphamate, saccharinate and chloride anions-was assayed with respect to their inhibitory activity towards acetylcholinesterase and their cellular toxicity towards the IPC-81 rat promyelocytic leukaemia cell line: the acute biological activity of these compounds is very low. Effective concentrations lie in the millimole range, which is well above possible intracellular concentrations. Only the compounds with the longest alkoxymethyl chain inhibit the enzyme at effective concentrations that are one order of magnitude smaller. No significant differences are observed when the anion compartment in the enzymatic assay is varied. However, the cytotoxicity data show EC(50) for acesulphamates and saccharinates to be higher than the values for the chloride analogues. Also, a slight alkoxymethyl chain length effect on the overall cytotoxicity is discernible. The biodegradability of the 1-alkoxymethyl-3-hydroxypyridinium salts varies from 21% to 72% and depends on the type of anion the cation is linked with. It improves with lengthening alkyl chain, but only in the range from 4 to 11 carbon atoms.
Asunto(s)
Cloruros/química , Líquidos Iónicos/química , Ácidos Sulfónicos/química , Tiazoles/química , Animales , Aniones/química , Bacterias/metabolismo , Biodegradación Ambiental , Línea Celular Tumoral , Cloruros/farmacología , Cloruros/toxicidad , Inhibidores de la Colinesterasa , Relación Dosis-Respuesta a Droga , Líquidos Iónicos/metabolismo , Estructura Molecular , Ratas , Ácidos Sulfónicos/metabolismo , Ácidos Sulfónicos/farmacología , Tiazoles/farmacología , Tiazoles/toxicidadRESUMEN
The study examined the usefulness of a Fenton-like system for the degradation of ionic liquid residues in water. The ionic liquid was oxidized in a dilute aqueous solution of 1-butyl-3-methylimidazolium chloride (bmimCl). The ionic liquid decomposes readily and rapidly in aqueous solution by chemical degradation in a Fenton-like system. Under chosen conditions the initial bmimCl solution was reduced by a factor of 0.973 within 90 min. Additional results showed that bmimCl degradations in a Fenton-like system in excess H2O2 could be interpreted as a combined oxidation-reduction mechanism. Preliminary investigations of the mechanism of such degradations have indicated that initial OH* radicals can attack any one of the three carbon atoms on the imidazolium ring. The intermediates of this reaction may be mono- di- or amino- carboxylic acids.
Asunto(s)
Peróxido de Hidrógeno/química , Imidazoles/química , Hierro/química , Oxidantes/química , Contaminantes Químicos del Agua/química , Ácidos Carboxílicos/química , Concentración de Iones de Hidrógeno , Oxidación-Reducción , Purificación del Agua/métodosRESUMEN
In order to rise efficiency of the wastewater treatment in a refinery plant, several oxidation experiments were done, testing their applicability as an additional pretreatment method. The influence of treatment with low concentrations of H2O2 combined with stirring and UV light on degradation of organic compounds present in the refinery wastewater was studied. Oxidation of the total petroleum hydrocarbons occurs at relatively low concentrations of H2O2, additional UV irradiation slightly accelerates the process due to the increased formation of hydroxyl radicals. 1,2-dichloroethane and t-butyl methyl ether degrade in the similar manner and except for the lowest H2O2 concentration used (1.17 mM), the reduction after 24 h is total. The degradation rate for dichloromethane is the lowest one, depending both on hydrogen peroxide concentration and the presence of UV. Its maximum reduction of 83% was obtained using the highest applied peroxide concentration of 11.76 mM.