Browsing by Subject "Kinetic studies"

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    Modulating the catalytic activity by the mechanical bond: organocatalysis with polyamide [2]rotaxanes bearing a secondary amino function at the thread
    (Royal Society of Chemistry, 2022-04-06) Pérez Martínez, Jesús de María; Alajarín, Mateo; Martinez-Cuezva, Alberto; Berná Cánovas, José; Química Orgánica
    The modulation of the catalytic activity of degenerate succinamide-based [2]rotaxanes by changes at their macrocyclic component is disclosed herein. These systems, bearing an acyclic secondary amine function at the thread as the active site and incorporating different polyamide macrocycles, were evaluated as organocatalysts in iminium- and enamine-type processes. The results of kinetic studies clearly show a drastic variation of their catalytic efficiency, which apparently correlated with the electronics and dynamics of the entwined macrocycle.
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    Total removal of Hg (II) from wastewater using magnetic nanoparticles coated with nanometric Ag and functionalized with sodium 2-mercaptoethane sulfonate
    (Springer Nature, 2020-03-17) Vicente Martínez, Yésica; Caravaca, Manuel; Soto Meca, Antonio; Química Analítica
    Divalent mercury (Hg (II)) is the predominant mercury species in aquatic environments. Hg (II) combines easily with human enzymes, thus causing acute diseases, even at very low concentrations. Among existing procedures to remove Hg (II) from water, adsorption is widely used, achieving high removal efficiencies. However, most actual adsorption techniques require high temperatures, long times or tedious procedures. Here we present a novel, simple and fast method to remove Hg (II) from wastewater by using magnetic-core nanoparticles coated with metallic silver and functionalized with sodium 2-mercaptoethane sulfonate. This adsorbent was characterized by field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy and Brunauer–Emmett–Teller analysis, which showed a contact surface area of the adsorbent equal to 116.476 m2/g. The equilibrium isotherm is characterized by the Langmuir model. Results show that 100% adsorption efficiency is achieved in 30 seconds of contact time, at pH 6.2 and room temperature, employing a low dose of adsorbent. The adsorbent can be recovered and recycled, keeping 100% adsorption efficiency for two additional cycles. The presence of other ions commonly found in aqueous media does not interfere with Hg (II) adsorption.