Examinando por Autor "Ojeda, Juan"

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    Effect of the Incorporation of Ni in the Adsorption Capacity of Paracetamol (N-Acetyl-P-Aminophenol) on MIL-101(Cr).
    (Springer Nature, 2020) Ojeda, Juan
    The effect of nickel in the adsorption of Nacetyl-p-aminophenol (paracetamol) on a metal-organic frameworks (MOFs) type MIL-101(Cr) was studied. The incorporation of Ni to MOFs adsorbent was carried out by impregnation and adjusted to give a 4.00 wt.% Ni. The adsorbents were characterized by specific surface area (SSA), surface acidity techniques, electrophoretic migration (EM), thermogravimetric analysis (TGA), and scanning electron microscope (SEM) and were tested by the adsorption of paracetamol solutions. The results showed that the Ni particles were well dispersed throughout the MIL-101(Cr) crystal increasing the acid strength and the density of acid site values in the MOFs surface. The increase in adsorption capacity of MIL-101(Cr) when Ni was incorporated can be attributed to the availability of metal atoms as adsorption centers that can adsorb the paracetamol by electronic retro-donation through π-type complexing.
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    Simultaneous Adsorption of 4,6-Dimethyldibenzothiophene and Quinoline over Nickel and Boron Modified Gamma-Al2O3 Adsorbent
    (MDPI, 2020) Ojeda, Juan
    The simultaneous adsorption of quinoline and 4,6-dimethyldibenzothiophene over adsorbents, based on alumina modified with boron and nickel under ambient temperature and pressure, was studied. The adsorbents were characterized by BET specific surface area, a potentiometric method for the determination of acid strength, electrophoretic migration, and X-ray diffraction. The results showed that the adsorbent containing nickel had better adsorption capacity than the adsorbent modified with nickel and boron, which was attributed to its greater acidity and ability to generate π-complexation between the adsorbent and the molecules. In terms of selectivity, quinoline was more adsorbed than 4,6-dimethyldibenzothiophene in all systems, due to the basic nature of quinoline. The experimental data in all cases were adjusted by three kinetic models (Yoon–Nelson, Yan and Thomas), and the regression coefficients in all models were close to one. Finally, the values of the kinetic constant obtained by the Thomas model were used to relate the adsorption capacity results. View Full-Text
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    Sulfur or Pollen? Chemical, Biological, and Toxicological Basis for the Correct Risk Communication of Urban Yellow Dust Deposition
    (Springer Nature, 2020) Ojeda, Juan; Goddard, Marcela; Cavieres, María Fernanda
    Urban yellow dust deposition is a common phenomenon in many parts of the world, which is sometimes called “sulfur shower,” “sulfur rain,” or “pollen storm.” Most people, especially those living in the vicinity of industrial facilities, wrongly perceive the yellow dust as sulfur when in fact it is pollen. The misunderstanding increases risk perception as people believe the “yellow powder” is a serious threat to their health. Based on simple observations, it is virtually impossible to differentiate sulfur from pollen, so risk communication should consider the chemical, biological, and toxicological aspects of these agents. In this review, we clarify that industrial emissions of sulfur are under the form of sulfides, oxides, and other volatile compounds which are gaseous and noncolored, and we explain that it is chemically impossible for gaseous sulfur to become solid yellow sulfur under normal environmental conditions. We also describe pollen and its release from trees, shrubs, and herbs a process influenced by atmospheric conditions. We suggest take-home messages that risk communicators may use when explaining the phenomenon to their communities.
  • Miniatura
    Ítem
    Sulfur or pollen? Chemical, biological, and toxicological basis for the Correct risk communication of urban yellow dust deposition
    (Springer Nature, 2020) Ojeda, Juan; Goddard, Marcela; Cavieres, María Fernanda; Baeza, Patricio
    Urban yellow dust deposition is a common phenomenon in many parts of the world, which is sometimes called “sulfur shower,” “sulfur rain,” or “pollen storm.” Most people, especially those living in the vicinity of industrial facilities, wrongly perceive the yellow dust as sulfur when in fact it is pollen. The misunderstanding increases risk perception as people believe the “yellow powder” is a serious threat to their health. Based on simple observations, it is virtually impossible to differentiate sulfur from pollen, so risk communication should consider the chemical, biological, and toxicological aspects of these agents. In this review, we clarify that industrial emissions of sulfur are under the form of sulfides, oxides, and other volatile compounds which are gaseous and noncolored, and we explain that it is chemically impossible for gaseous sulfur to become solid yellow sulfur under normal environmental conditions. We also describe pollen and its release from trees, shrubs, and herbs a process influenced by atmospheric conditions. We suggest take-home messages that risk communicators may use when explaining the phenomenon to their communities.