Navegando por Autor "Lage, Mateus R."

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Adsorption of the herbicides diquat and difenzoquat on polyurethane foam: kinetic, equilibrium and computational studies
(Ecotoxicology and Environmental Safety, 2017-08-09) Vinhal, Jonas O.; Nege, Kassem K.; Lage, Mateus R.; Carneiro, José Walkimar de M.; Lima, Claudio F.; Cassella, Ricardo J.
This work reports a study about the adsorption of the herbicides diquat and difenzoquat from aqueous medium employing polyurethane foam (PUF) as the adsorbent and sodium dodecylsulfate (SDS) as the counter ion. The adsorption efficiency was shown to be dependent on the concentration of SDS in solution, since the formation of an ion-associate between cationic herbicides (diquat and difenzoquat) and anionic dodecylsulfate is a fundamental step of the process. A computational study was carried out to identify the possible structure of the ion-associates that are formed in solution. They are probably formed by three units of dodecylsulfate bound to one unit of diquat, and two units of dodecylsulfate bound to one unit of difenzoquat. The results obtained also showed that 95% of both herbicides present in 45 mL of a solution containing 5.5 mg L^−1 could be retained by 300 mg of PUF. The experimental data were well adjusted to the Freundlich isotherm (r^2 ≥ 0.95) and to the pseudo-second-order kinetic equation. Also, the application of Morris-Weber and Reichenberg equations indicated that an intraparticle diffusion process is active in the control of adsorption kinetics.
Modeling, kinetic, and equilibrium characterization of paraquat adsorption onto polyurethane foam using the ion-pairing technique
(Journal of Environmental Management, 2015-06-01) Vinhal, Jonas O.; Lage, Mateus R.; Carneiro, Jose Walkimar M.; Lima, Claudio F.; Cassella, Ricardo J.
We studied the adsorption of paraquat onto polyurethane foam (PUF) when it was in a medium containing sodium dodecylsulfate (SDS). The adsorption efficiency was dependent on the concentration of SDS in solution, because the formation of an ion-associate between the cationic paraquat and the dodecylsulfate anion was found to be a fundamental step in the process. A computational study was carried out to identify the possible structure of the ion-associate in aqueous medium. The obtained data demonstrated that the structure is probably formed from four units of dodecylsulfate bonded to one paraquat moiety. The results showed that 94% of the paraquat present in 45 mL of a solution containing 3.90 × 10^−5 mol L^−1 could be retained by 300 mg of PUF, resulting in the removal of 2.20 mg of paraquat. The experimental data were reasonably adjusted to the Freundlich isotherm and to the pseudo-second-order kinetic model. Also, the application of Morris–Weber and Reichenberg models indicated that both film-diffusion and intraparticle-diffusion processes were active during the control of the adsorption kinetics.
Natural polyprenylated benzophenone: keto-enol tautomerism from density functional calculations and the AIM theory
(Journal of Molecular Modeling, 2017-03-30) Santos, Marcelo H.; Lage, Mateus R.; Morbec, Juliana M.; Carneiro, José Walkimar de M.; Costa, Luciano T.
The quantum theory of atoms in molecules (QTAIM) and density functional theory (DFT) calculations were employed to investigate the structure and tautomeric equilibrium of epiclusianone, a polyisoprenylated benzophenone with interesting biological activities. Two different exchange-correlation functionals were employed, namely ωB97x-D and M06-2x, including implicit solvent models (benzene and DMSO). Our results for the thermodynamic properties show that the isomer in which the H atom is bonded to the oxygen away from the benzene ring is the most stable tautomer form of the epiclusianone, thus confirming previous charge density analysis from X-ray diffraction data (Martins et al. J Braz Chem Soc 18(8):1515–1523, 2007).