Browsing by Author "Garrido, Carlos"

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    Multimetallic porphyrins/polyoxotungstate modified electrodes by layer-by-layer method: Electrochemical, spectroscopic and morphological characterization
    (PERGAMON-ELSEVIER SCIENCE LTD, 2012) Garcia, Macarena; Carfuman, Karla; Diaz, Carlos; Garrido, Carlos; Osorio Roman, Igor; Jesus Aguirre, M.; Isaacs, Mauricio
    This work describes the formation of modified electrodes layer-by-layer assembly of a mu-{meso-5,10,15,20-tetra(pyridyl)porphyrin}terrakis{bis(bipyridine)chloride ruthenium(II)} coordinated with Zn(II) and Mn(III) in its central cavity and an anionic polyoxotungstate [SiW12O40](4-). The bilayer formation was monitored using electrochemical and UV-vis techniques, following the oxidation process of the Ru-III/II couple and the absorbance of the Soret band of porphyrin complexes respectively. It was possible to form 10 stable bilayers onto ITO surface. SEM studies were carried out finding that the morphology of the film depends on the metal center in the porphyrin. The thickness of these films was estimated as 0.603 mu m for (Zn(II)TRP](4+)/[SiW12O40](4-) and 2.18 mu m for [Mn(III)TRP](5+)/[[SiW12O40](4-) modified electrodes respectively. Raman spectroscopy showed that new bands appeared for [Mn(III)TRP](5+)/[SIW12O40](4-) assembly confirming stronger interactions than only electrostatic forces.
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    Study of Sorption Kinetics and Sorption-Desorption Models to Assess the Transport Mechanisms of 2,4-Dichlorophenoxyacetic Acid on Volcanic Soils
    (2021) Caceres-Jensen, Lizethly; Rodriguez-Becerra, Jorge; Garrido, Carlos; Escudey, Mauricio; Barrientos, Lorena; Parra-Rivero, Jocelyn; Dominguez-Vera, Valentina; Loch-Arellano, Bruno
    The sorption behavior of 2,4-dichlorophenoxyacetic acid (2,4-D) in the abundant agricultural volcanic ash-derived soils (VADS) is not well understood despite being widely used throughout the world, causing effects to the environment and human health. The environmental behavior and risk assessment of groundwater pollution by pesticides can be evaluated through kinetic models. This study evaluated the sorption kinetics and 2,4-D sorption-desorption in ten VADS through batch sorption experiments. Differences in the sorption extent for the fast and slow phases was observed through the IPD model where 2,4-D sorption kinetics was controlled by external mass transfer and intra organic matter diffusion in Andisols (C1 not equal 0). We confirmed from the spectroscopic analysis that the carboxylate group directly drives the interaction of 2,4-D on Andisol soil. The MLR model showed that IEP, FeDCB, and pHxSilt are important soil descriptors in the 2,4-D sorption in VADS. The Freundlich model accurately represented sorption equilibrium data in all cases (Kf values between 1.1 and 24.1 mu g(1-1/n) mL(1/n)g(-1)) with comparatively higher sorption capacity on Andisols, where the highest hysteresis was observed in soils that presented the highest and lowest OC content (H close to 0).