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14 results on '"Caceres‐Jensen, Lizethly"'

3. Role of Nb2O5 Crystal Phases on the Photocatalytic Conversion of Lignin Model Molecules and Selectivity for Value‐Added Products.

Author

Rojas, Susana D., Rafaela, Gabriela, Espinoza‐Villalobos, Nicole, Diaz‐Droguett, Donovan E., Salazar‐González, Ricardo, Caceres‐Jensen, Lizethly, Escalona, Néstor, and Barrientos, Lorena

Subjects
HYDROXYL group, MOLECULES, PHOTOCATALYTIC oxidation, CRYSTALS, CRYSTAL morphology, LIGNINS, LIGNANS, LIGNIN structure
Abstract

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. [ABSTRACT FROM AUTHOR]

Published
2024
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10. Impact of Physical/Chemical Properties of Volcanic Ash-Derived Soils on Mechanisms Involved during Sorption of Ionisable and Non-Ionisable Herbicides

Author

Caceres Jensen, Lizethly, Escudey, Mauricio, and Rodríguez Becerra, Jorge

Subjects
Science / Chemistry
Abstract

Volcanic ash-derived soils (VADSs) are of great importance in the agricultural economy of several emerging and developing countries. The surface-charge amphoteric characteristics will confer physical/chemical properties absolutely different to constant-charge soils. This surface reactivity will confer to them a particular behaviour in relation to the herbicide sorption, representing an environmental substrate that may become polluted over time due to intensive agronomic uses. Sorption is a key parameter to evaluate the fate and behaviour of herbicides in volcanic soils. Sorption type and kinetic sorption models are also necessary in order to develop and validate QSAR models to predict pesticide sorption on volcanic soils to prevent potential contamination of water resources. The use of solute sorption mechanism models and QSAR models for pesticide sorption in soils has contributed to a better understanding of the behaviour of pesticides on volcanic soils. This chapter is divided into five sections: Physical/chemical properties of volcanic ash-derived soils; Ionisable and non-ionisable herbicides’ fate and behaviour in soil; Kinetic sorption: mechanisms involved during sorption of ionisable and non-ionisable herbicides on VADS; Sorption of ionisable and non-ionisable herbicides on VADS; and Physical/chemical properties in QSAR models: a mechanistic interpretation.

Published
2022

11. Insect Epigenetic Mechanisms Facing Anthropogenic-Derived Contamination, an Overview

Author

Olivares-Castro, Gabriela, Caceres-Jensen, Lizethly, Guerrero-Bosagna, Carlos M., Villagra, Cristian, Olivares-Castro, Gabriela, Caceres-Jensen, Lizethly, Guerrero-Bosagna, Carlos M., and Villagra, Cristian

Abstract

Simple Summary Epigenetic molecular mechanisms (EMMs) are capable of regulating and stabilizing a wide range of living cell processes without altering its DNA sequence. EMMs can be triggered by environmental inputs. In insects, EMMs contribute to explaining both negative effects as well as adaptive responses towards environmental cues. Among these stimuli are chemical stressors, such as pesticides. We review the link between EMMs and pesticides in insects. We suggest that pesticide chemical behavior promotes both lethal and sublethal exposure of both target and non-target insects. As a consequence, for several native and beneficial insect (e.g., pollinators), EMMs are involved in diseases and disruptive responses due to pesticides, while in the case of pest species, EMMs are linked in the development of pesticide resistance and hormesis. We discuss the consequences of these in the context of insect global decline and biotic homogenization. Currently, the human species has been recognized as the primary species responsible for Earth's biodiversity decline. Contamination by different chemical compounds, such as pesticides, is among the main causes of population decreases and species extinction. Insects are key for ecosystem maintenance; unfortunately, their populations are being drastically affected by human-derived disturbances. Pesticides, applied in agricultural and urban environments, are capable of polluting soil and water sources, reaching non-target organisms (native and introduced). Pesticides alter insect's development, physiology, and inheritance. Recently, a link between pesticide effects on insects and their epigenetic molecular mechanisms (EMMs) has been demonstrated. EMMs are capable of regulating gene expression without modifying genetic sequences, resulting in the expression of different stress responses as well as compensatory mechanisms. In this work, we review the main anthropogenic contaminants capable of affecting insect biology and of triggering

Published
2021
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12. Herbicides Mechanisms Involved in the Sorption Kinetic of Ionisable and Non Ionisable Herbicides : Impact of Physical/Chemical Properties of Soils and Experimental Conditions

Author

Caceres Jensen, Lizethly, Neira Albornoz, Angelo, and Escudey, Mauricio

Subjects
Science / Physics
Abstract

Volcanic ash-derived soils (VADS, variable-charge soils) are predominant in some regions of the world, being of great importance in the agricultural economy of several emerging countries. Their amphoteric surface charge characteristics confer physical/chemical properties different to constant surface charge-soils, showing a particular behavior in relation to the herbicide adsorption kinetics. Volcanic soils represent an environmental substrate that may become polluted over time due to intensive agronomic uses. Solute transport models have contributed to a better understanding of herbicide behavior on variable- and constant-charge soils, being also necessary to evaluate the fate of herbicides and to prevent potential contamination of water resources. The following chapter is divided into four sections: physical/chemical properties of variable and constant-charge soils, kinetic adsorption models frequently used to obtain kinetic parameters of herbicides on soils, solute transport models to describe herbicide adsorption on VADS, and impact of experimental conditions of kinetic batch studies on solute transport mechanisms.

Published
2019

14. Role of Nb 2 O 5 Crystal Phases on the Photocatalytic Conversion of Lignin Model Molecules and Selectivity for Value-Added Products.

Author

Rojas SD, Rafaela G, Espinoza-Villalobos N, Diaz-Droguett DE, Salazar-González R, Caceres-Jensen L, Escalona N, and Barrientos L

Abstract

The photocatalytic conversion in aqueous media of phenol and guaiacol as a lignin model compound using Nb 2 O 5 with different crystal phases was studied. Nb 2 O 5 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 Nb 2 O 5 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 Nb 2 O 5 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 Nb 2 O 5 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., (© 2024 Wiley-VCH GmbH.)

Published
2024
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