The kinetic reactions of 1,2-benzenediol (catechol) and 2-methoxyphenol (guaiacol) with ozone were studied in a simulation chamber (8 m(3)) under dark conditions. The rate coefficients were measured at 294 ± 2 K, atmospheric pressure and dry conditions (relative humidity, RH < 1%), except for 1,2-benzenediol where they were also measured as a function of relative humidity (RH = 1-80%). The concentrations of organic compounds were followed by a PTR-ToF-MS for a continuous monitoring of gas-phase species. The O3 rate coefficients were obtained using both the pseudo-first-order and relative rate methods. The values (in cm(3) molecule(-1) s(-1)) determined for catechol and guaiacol under dry conditions are (13.5 ± 1.1) × 10(-18) and (0.40 ± 0.31) × 10(-18), respectively. The rate coefficient of catechol was found to be independent of RH below 20% and above 60%, whereas for RH between 20% and 60% it decreases with increasing RH. The determined rate coefficients have been used to evaluate the atmospheric lifetime of each compound with respect to O3. To our knowledge, this study represents the first determination of the ozone rate coefficient with guaiacol and is also the first kinetic investigation for the influence of the relative humidity on the oxygenated aromatic ozonolysis.
The gas-phase reactions of five methoxyphenols (three disubstituted and two trisubstituted) with nitrate radicals were studied in an 8000 L atmospheric simulation chamber at atmospheric pressure and 294 ± 2 K. The NO3 rate constants were investigated with the relative kinetic method using PTR-ToF-MS and GC-FID to measure the concentrations of the organic compounds. The rate constants (in units of cm(3) molecule(-1) s(-1)) determined were: 2-methoxyphenol (guaiacol; 2-MP), k(2-MP) = (2.69 ± 0.57 × 10(-11); 3-methoxyphenol (3-MP), k(3-MP) = (1.15 ± 0.21) × 10(-11); 4-methoxyphenol (4-MP), k(4-MP) = (13.75 ± 7.97) × 10(-11); 2-methoxy-4-methylphenol, k(2-M-4-MeP) = (8.41 ± 5.58) × 10(-11) and 2,6-dimethoxyphenol (syringol; 2,6-DMP), k(2,6-DMP) = (15.84 ± 8.10) × 10(-11). The NO3 rate constants of the studied methoxyphenols are compared with those of other substituted aromatics, and the differences in the reactivity are construed regarding the substituents (type, number and position) on the aromatic ring. This study was also supplemented by a theoretical approach of the methoxyphenol reactions with nitrate radicals. The upper limits of the NO3 overall rate constants calculated were in the same order of magnitude than those experimentally determined. Theoretical calculations of the minimum energies of the adducts formed from the reaction of NO3 radicals with the methoxyphenols were also performed using a DFT approach (M06-2X/6-31G(d,p)). The results indicate that the NO3 addition reactions on the aromatic ring of the methoxyphenols are exothermic, with energy values ranging between -13 and -21 kcal mol(-1), depending on the environment of the carbon on which the oxygen atom of NO3 is attached. These energy values allowed identifying the most suitable carbon sites for the NO3 addition on the aromatic ring of the methoxyphenols: at the exception of the 3-MP, the NO3 ipso-addition to the hydroxyl group is one of the favored sites for all the studies compounds.
AIR+HDO:ESO:LLI:PVEPlatinum nanoparticles of narrow size distribution (similar to 2.5 nm) were synthesized using a modified polyol method and deposited on yttria-stabilized zirconia (Pt/YSZ), carbon (Pt/C) and gamma-alumina (Pt/gamma-Al2O3) supports, resulting in 1 wt % of Pt loading. Pt/YSZ has the highest catalytic activity toward CO oxidation among the studied catalysts. Decrease in the average particle size of Pt/YSZ led to the increase in CO conversion at low temperatures. Enhanced performances can be explained by the thermally induced O2- backspillover from YSZ over Pt nanoparticles in agreement with the electrochemical promotion mechanism. Observed effect becomes more pronounced with decreasing the particle size. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.024203esl] All rights reserved
Water pollution is caused by multiple factors, such as industrial dye wastewater. Dye-contaminated water can be treated using hydrogels as adsorbent materials. Recently, composite hydrogels containing metal oxide nanoparticles (MONPs) have been used extensively in wastewater remediation. In this study, we use a statistical and artificial intelligence method, based on principal component analysis (PCA) with different applied parameters, to evaluate the adsorption efficiency of 27 different MONP composite hydrogels for wastewater dye treatment. PCA showed that the hydrogel composites CTS@Fe3O4, PAAm/TiO2, and PEGDMA-rGO/Fe3O4@cellulose should be used in situations involving high pH, time to reach equilibrium, and adsorption capacity. However, as the composites PAAm-co-AAc/TiO2, PVPA/Fe3O4@SiO2, PMOA/ATP/Fe3O4, and PVPA/Fe3O4@SiO2, are preferred when all physical and chemical properties investigated have low magnitudes. To conclude, PCA is a strong method for highlighting the essential factors affecting hydrogel composite selection for dye-contaminated water treatment.
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