Rate coefficients for the reactions of hydroxyl radicals and chlorine atoms with methyl crotonate and ethyl crotonate have been determined at 298 K and atmospheric pressure. The decay of the organics was monitored using gas chromatography with flame ionization detection (GC-FID), and the rate constants were determined using the relative rate method with different reference compounds. Room temperature rate coeficcients were found to be (in cm(3) molecule(-1) s(-1)): k(1)(OH + CH(3)CH═CHC(O)OCH(3)) = (4.65 ± 0.65) × 10(-11), k(2)(Cl + CH(3)CH═CHC(O)OCH(3)) = (2.20 ± 0.55) × 10(-10), k(3)(OH + CH(3)CH═CHC(O)OCH(2)CH(3)) = (4.96 ± 0.61) × 10(-11), and k(4)(Cl + CH(3)CH═CHC(O)OCH(2)CH(3)) = (2.52 ± 0.62) × 10(-10) with uncertainties representing ±2σ. This is the first determination of k(1), k(3), and k(4) under atmospheric pressure. The rate coefficients are compared with previous determinations for other unsaturated and oxygenated VOCs and reactivity trends are presented. In addition, a comparison between the experimentally determined k(OH) with k(OH) predicted from k vs E(HOMO) relationships is presented. On the other hand, product identification under atmospheric conditions has been performed for the first time for these unsaturated esters by the GC-MS technique in NO(x)-free conditions. 2-Hydroxypropanal, acetaldehyde, formaldehyde, and formic acid were positively observed as degradation products in agreement with the addition of OH to C2 and C3 of the double bond, followed by decomposition of the 2,3- or 3,2-hydroxyalkoxy radicals formed. Atmospheric lifetimes, based on of the homogeneous sinks of the unsaturated esters studied, are estimated from the kinetic data obtained in the present work.
Given the species A 1 and A 2 , the competition among the three different elementary processesis frequently found in thermal and photochemical reaction systems. In the present paper, an analytical resolution of the system (1) The comparison with a numerical integration employing the fourth-order Runge-Kutta algorithm for the well-known case of the oxidation of organic compounds by ferrate ion is performed.
The aim of this work was to study of the kinetic of Pb(II) sorption, in high lead concentration aqueous solution, by the natural hydroxyapatite (HA) and to verify whether there is a different behavior between natural and synthetic HA under different lead concentrations. Batch experiments were carried out using solutions with high lead concentration, with the objective to evaluate the effect of contact time, HA dosage and initial metal concentration on lead removal. Kinetic data were analyzed by pseudo-first and pseudo-second order models. The sorption data was then correlated with the Langmuir and Freundlich isotherm models. The PZC obtained was slightly different than those reported by other authors, who evaluated the process under low concentrations and synthetic HA as adsorbent. It was possible to identify the optimum relation between Pb(II) concentrations and mass of HA for efficiency of approximately 100% at optimum contact time. Although the results show a certain instability during the removal of lead when the concentration is much higher, the process can be considered effective. Liquid samples were analyzed by atomic absorption spectroscopy and solid samples were by X-ray diffraction and Fourier transform infrared spectroscopy.
ABSTRACT:The campus of San Lorenzo has 18 artesian wells that provide water to the different academic units , six of which showed varying degrees of bacterial contamination which were monitored in the laboratory in order to select one to perform tests disinfection . The degree of contamination of these was determined , choosing the one with highest bacterial load , represented by E. coli , to take the samples, were subjected to treatment using the technique of Solar Heterogeneous photocatalysis using TiO 2 (titanium dioxide ) as a catalyst . The treatment was performed at different times of year, July 2010 to September 2011 using a spherical static reactor mounted on a metal stand with a reflective surface mobile polished aluminum, the working temperature was maintained between 15-45 ° C and samples were taken at time intervals of 1.5 to 5 hours of exposure to solar radiation. The results obtained by this method confirm its effectiveness, even with minimal exposure time, no bacterial growth was observed within 48 h after treatment.
A comunidade Y´Apy Santa Isabel é uma comunidade indígena localizada no Departamento de San Pedro, Paraguai. Seus meios de subsistência dependem do que a natureza lhes fornece, o que os torna particularmente vulneráveis aos efeitos das mudanças climáticas e suscetíveis a eventos climáticos extremos que afetam suas atividades diárias. Eles têm uma percepção clara de que há mudanças no clima de acordo com as evidências registradas nos dados da Estação Meteorológica de San Estanislao (EMSE) que indicam que eventos extremos de precipitação, ondas de calor e frio estão aumentando na região. A análise estatística dos dados meteorológicos do EMSE foi conduzida e entrevistas foram conduzidas com as principais partes interessadas da comunidade para coletar dados sobre os meios de subsistência e capitais da comunidade. Nos últimos 10 anos, ocorreram 41 eventos extremos de precipitação, 22 eventos de ondas de frio e 13 eventos de ondas de calor que afetaram principalmente o capital físico e humano.
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