Photoelectron Spectroscopy and Ionic Fragmentation of OSeCl2 and Its Analogue OSCl2 under VUV Irradiation.

The electronic structure and the dissociative ionization of selenium oxychloride, OSeCl2, have been investigated in the valence region by using results from both photoelectron spectroscopy (PES) and synchrotron-based photoelectron photoion coincidence (PEPICO) spectra. The PES is assigned with the help of quantum chemical calculations at the outer-valence Green's function (OVGF) and symmetry adapted cluster/configuration interaction (SAC-CI) levels. The first energy ionization is observed at 11.47 eV assigned to the ionization of electrons formally delocalized over the Se, Cl, and O lone pair orbitals. Irradiation of OSeCl2 with photons in the valence region leads to the formation of OSeCl2(•+), OSeCl(+), SeCl2(•+), SeCl(+), and SeO(•+) ions. Furthermore, the inner shell Se 3p, Cl 2p, and Se 3s electronic regions of OSeCl2 together with S 2p, Cl 2p, and S 2s electronic regions of thionyl chloride, OSCl2, have been studied by using tunable synchrotron radiation. Thus, total ion yield spectra and the fragmentation patterns deduced from PEPICO spectra at the various excitation energies have been studied. Cl(+), O(•+), and Se(•+) ions appear as the most intense fragments in the OSeCl2 PEPICO spectra, like in the sulfur analogue OSCl2, whose photofragmentation is dominated by the Cl(+), O(•+), and S(•+) ions. Fragmentation processes in OSCl2 leading to the formation of the double coincidences involving atomic ions appear as the most intense in the PEPIPICO spectra.

Synergistic effects between SO2 and HCOOH on α-Fe2O3.

Heterogeneous reactions on mineral aerosols remain an important subject in atmospheric chemistry because of their role in altering the properties of particles and the budget of trace gases. Yet, the role of coadsorption of trace gases onto mineral aerosols and potential synergistic effects are largely uncertain, especially synergistic effects between inorganic and organic gas-phase pollutants. In this study, synergistic effects between HCOOH and SO2 were investigated for the first time using in situ diffuse-reflectance infrared Fourier transform spectroscopy (DRIFTS). It was found that the heterogeneous reaction of HCOOH is hindered significantly by coexisting SO2. The total amount of formate decreased, whereas the total amount of sulfate was not affected during coadsorption on the surface of α-Fe2O3. Futhermore, part of the formate on the surface was catalytically decomposed to CO2 by α-Fe2O3 with the help of SO2. These results suggest a possible mechanism for the observed correlations between sulfate and carboxylate in the atmosphere.

Influence of temperature on the heterogeneous reaction of formic acid on α-Al2O3.

Despite increased awareness of the role played by heterogeneous reactions of formic acid on mineral aerosol, the experimental determination of how these atmospheric reaction rates vary with temperature remain a crucially important part of atmosphere science. Here we report the first measurement of heterogeneous uptake of formic acid on α-Al(2)O(3) as a function of temperature (T = 240-298 K) at ambient pressure using diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). From the analysis of the spectral features, crystalline HCOOH was identified at low temperature besides common product (formate ions) on the surface. It was also interesting to find that crystalline HCOOH can continue to react with α-Al(2)O(3). The reaction mechanisms at both room and low temperature were discussed. Furthermore, the reactive uptake coefficients were acquired and found to increase with decreasing temperature. Finally, the atmospheric lifetime of formic acid because of heterogeneous loss on mineral aerosol was estimated at temperatures related to the upper troposphere.

Fe3+ and amino functioned mesoporous silica: preparation, structural analysis and arsenic adsorption.

Two novel adsorbents to remove excess arsenate and arsenite in the drinking water were prepared for the first time by grafting monoamine and diamine, respectively, and then coordinating Fe(3+) on silica gel that was obtained using sol-gel method with two-step acid-base catalysis. It was found that both adsorbents had mesoporous structure, large specific surface, and high amino and iron content according to N(2) adsorption isotherms, FTIR, XPS, and NMR analysis. The removal ability and adsorption rate of the adsorbents were very high for both As(V) and As(III). Langmuir and Freundlich models were used to fit the adsorption isotherm and investigate the adsorption mechanism. The effects of chloride and sulfate anion on the removal of arsenate and arsenite for the two adsorbents were also studied.