Browsing by Author "Cáceres Jensen, Lizethly"

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    Role of Nb2O5 Crystal Phases on the Photocatalytic Conversion of Lignin Model Molecules and Selectivity for Value‐Added Products
    (2024) Rojas de la Fuente, Susana Dennis; Rafaela, Gabriela; Espinoza Villalobos, Nicole Margarita; Díaz, Donovan; Salazar, Ricardo; Cáceres Jensen, Lizethly; Escalona, Néstor; Barrientos, Lorena
    The photocatalytic conversion in aqueous media of phenol and guaiacol as a lignin model compound using Nb2O5 with different crystal phases was studied. Nb2O5 particles were synthesized using hydrothermal methods, where it was observed that changes in the solvent control their morphology and crystal phase. Different photocatalytic behavior of Nb2O5 was observed with the selected model compounds, indicating that its selection directly impacts the resulting conversion and selectivity rates as well as the reaction pathway, highlighting the relevance of model molecule selection. Photocatalytic conversion of phenol showed conversion rate (C%) up to 25 % after 2 h irradiation and high selectivity (S%) to pyrogallol (up to 50 %). Orthorhombic Nb2O5 spheres favored conversion through free hydroxyl radicals while monoclinic rods did not convert phenol. Guaiacol photocatalytic oxidation showed high conversion rate but lower selectivity. Orthorhombic and monoclinic Nb2O5 favored the formation of resorcinol with S % ~0.43 % (C % ~33 %) and ~13 % (C % ~27 %) respectively. The mixture of both phases enhanced the guaiacol conversion rate to ~55 % with ~17 % of selectivity to salicylaldehyde. The use of radical scavengers provided information to elucidate the reaction pathway for these model compounds, showing that different reaction pathways may be obtained for the same photocatalyst if the model compound is changed.
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    Transport mechanisms of the anthropogenic contaminant sulfamethoxazole in volcanic ash soils at equilibrium pH evaluated using the HYDRUS-1D model
    (2025) Urdiales, Cristian; Urdiales Flores, Diego; Tapia, Yasna; Cáceres Jensen, Lizethly; Simunek, Jirka; Antilén Lizana, Mónica Paulina
    The volcanic soils in Chile, where a significant portion of agricultural activities take place, are impacted by the presence of veterinary drugs, including sulfamethoxazole (SMX). The study examines how different soil types influence the movement and retention of sulfamethoxazole (SMX) across four regions of Chile, focusing on conditions at a neutral pH of 7.0. Collipulli's Ultisol soils (CLL), characterized by high clay and sand content but low organic matter (OM), promote low SMX adsorption and rapid transport. In contrast, the volcanic ash-derived Andisols from Frutillar (FRU), Nueva Braunau (NBR), and Osorno (OSR) have high OM and cation exchange capacity (CEC), which enhance their ability to retain SMX and reduce its mobility. Adsorption batch, kinetics, and column breakthrough curve (BTC) experiments were conducted alongside transport modelling. The adsorption kinetics of SMX in CLL soil followed a pseudo-first-order (PFO) model, while FRU, NBR, and OSR soils aligned with a pseudo-second-order (PSO) model. Freundlich isotherms effectively described SMX adsorption in CLL and OSR soils, indicating multilayer adsorption, while Langmuir isotherms fit the FRU and NBR soils, suggesting monolayer adsorption. Using HYDRUS-1D software, we simulated SMX transport in soil columns. BTCs were best modelled using a two-site sorption model with both equilibrium and kinetic adsorption. SMX was more mobile in CLL soil due to its lower organic matter (OM) content and adsorption capacity. In contrast, FRU, NBR, and OSR soils showed slower transport, reflecting higher OM content and greater adsorption capacity, reducing SMX leaching. These findings emphasize the importance of soil properties, such as OM content, in influencing SMX behavior, and are vital for assessing environmental impacts and developing mitigation strategies.