1,721,116 research outputs found
Intrinsic and environmental effects in the structure and magnetic properties of glycine radical in aqueous solution
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Geometry Optimization of Molecular Structures in Solution by the Polarizable Continuum Model
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Analytical expressions of the free energy derivatives for molecules in solution. Application to the geometry optimization.
No full textAnalytical derivatives for molecular solutes. III. Hartree-Fock static polarizability and hyperpolarizabilities in the polarizable continuum model.
No full textCavitation and Electrostatic Free Energy for Molecular Solutes in Liquid Crystals
No full textWe present an expression, based on scaled particle theory, for the calculation of cavitation free energy of molecules dissolved in nematic liquid crystals. This expression, depending on the orientation of the solute with respect to the director of the mesophase, completes the procedure, recently developed, for the calculation of electrostatic free energy in such systems, and allows the quantitative study of the orienting forces in anisotropic solutions. We report some applications to small rodlike molecules dissolved in a liquid crystal, for which the free energy orientational profile and the relevant elements of the Saupe matrix are calculated using ab initio HF 6-31G*
Adsorption of sulfonamide antibiotics onto high silica zeolites: from multidisciplinary model studies to applications to real waters
No full textOwing to their environmental diffusion and persistence, sulfonamide antibiotics (sulfa drugs) are
responsible to induce high level of resistance in bacteria. The sulfonamide anionic nature makes them
highly mobile along soil profile and is responsible for their accumulation into water bodies. In order
to limit the diffusion of resistance determinants, it is of utmost importance to identify adsorbents for
this antibiotic family to be adopted for water cleanup purpose. Three high silica zeolites (Y, MOR,
ZSM-5) have been tested for their capability to extract sulfonamides from water. Kinetics, capacity
and reversibility of the adsorption have been studied along with sulfonamide arrangement into the
porosities of each zeolite [1-3].
The sulfa drugs irreversibly adsorbed onto zeolite Y at ca. 26% on average and with the process
equilibrium reached in less than 1 min [1,3]. The favorable adsorption kinetics was confirmed when
zeolite Y was applied to both fresh and sea waters although the dissolved organic matter occurring
in natural water compartments can be retained as well but with a kinetics less favorable than that
shown by sulfa drugs. The main host-guest & guest-guest interactions between zeolites and sulfa drugs
were defined by IR and SS-NMR analysis, and augmented by computational studies. H-bonds and van
der Waals type interactions between single molecules and zeolite Y or ZSM-5 were responsible for
the irreversible extraction of sulfa drugs from water [1,3]. The occurrence of intramolecular medium
strength H-bond in small sized sulfa drugs upon adsorption inside zeolite Y cage revealed the formation
of dimeric species whose amidic or imidic tautomeric form were identified [1,3]. Rietveld refinement
and IR analysis revealed that sulfa drugs incorporation into MOR caused a close vicinity of the
heterocycle ring to the side pocket oxygens [2,3]. At 65°C, MOR gave rise to a sulfachloropyridazine
reaction product with a 100% selectivity and SNAr mechanism [2]. Among the regeneration strategies
approached, the thermal treatment and solvent extraction gave the best results.
References
[1] I. Braschi, G. Paul, G. Gatti, M. Cossi, L. Marchese. RSC Advances, 3, 7427 (2013).
[2] A. Martucci, M.A. Cremonini, S. Blasioli, L. Gigli, G. Gatti, L. Marchese, I. Braschi. Micropor.
Mesopor. Mat. 170, 274 (2013).
[3] S. Blasioli, A. Martucci, G. Paul, L. Gigli, M. Cossi, C.T Johnston, L. Marchese. J. Coll. Interface.
Sci., 419, 148 (2014)
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