Browsing by Author "Castro Tamay, Pablo Reinaldo"

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Obtención de microfibras de quitosano funcionalizadas con nanopartículas de Fe3O4 para su aplicación como adsorbente en la remoción de cromo (VI) en soluciones acuosas
(2019-04-13) Castro Tamay, Pablo Reinaldo; Vanegas Peña, María Eulalia
Cr (VI) species from industrial processes such as leather tanning, are highly toxic to living beings. In order to reduce the presence of these pollutants in water, various techniques have been used, where adsorption has proved to be an effective, economical and easy to apply method. Chitosan (CS) has been proven as a powerful heavy metal biosorbent, due to the large amount of hydroxyl and amino groups present in its main chain. Magnetite (Fe3O4), also has been used in the environmental field due to its adsorbing and reducing properties. Notable results have been achieved based on the combination of polymeric fibers and functional nanomaterials. In the present work, the synthesis of chitosan microfibers functionalized with nanoparticles (NPs) of Fe3O4 was performed to remove Cr (VI) from aqueous solutions. The NPs were synthesized by chemical co-precipitation and the CS/NPs fibers used in the removal of Cr (VI) from aqueous solutions were obtained by electrospinning. NPs were characterized by TEM, while the CS / NPs fibers were analyzed by SEM, FTIR and DSC. Cr (VI) in aqueous solution was measured using the colorimetric method of 1,5-diphenylcarbazide by UV-Vis spectroscopy. Micrometric interconnected structures of chitosan functionalized with NPs of Fe3O4 were obtained, in which fibers and beads (pearls or polymer agglomerations) of a few micrometers in size coexist. Cr (VI) removal percentage of 88.3% was reached under conditions of pH 3 and contact time of 9 min, in addition, it was determined that adsorption process is favored by increasing initial concentration of Cr (VI), dosage of the adsorbent and temperature. Also, the study of equilibrium and kinetic of adsorption was carried out, fitting better to Langmuir and Pseudo Second Order models, respectively.
Potential biopolymer adsorbent functionalized with Fe3O4 nanoparticles for the removal of Cr(VI) from aqueous solution
(2022) Vanegas Peña, María Eulalia; Castro Tamay, Pablo Reinaldo; Novoa, Néstor; Arrué, Ramón; Juela Quintuña, Diego Marcelo; Cruzat Contreras, Christian Américo
In the present study, an adsorbent with a synergistic effect was developed from chitosan (CS) and Fe3O4 nanoparticles (Fe3O4 Nps) to remove Cr(VI) from aqueous solutions. The Fe3O4 Nps were synthesized by co-precipitation and were characterized by TEM. The CS/NPs composites were prepared by electrospinning technique and analyzed by SEM, FT-IR, DSC, and TGA. In the batch system, the influence of Fe3O4 Nps content, pH, contact time, Cr(VI) initial concentration, adsorbent dosage, and the temperature was investigated; the Cr(VI) concentration was determined using a colorimetric method by UV–Vis spectroscopy. The Fe3O4 Nps presented a quasi-spherical shape and an average size of 18 nm, with a low particle distribution. The SEM analysis reveals the presence of highly porous, interconnected micrometric structures. The optimal adsorption conditions were 1% load of Fe3O4 Nps by weight of CS, pH 3, 25 °C, and equilibrium was reached at just 9 min. Besides, the adsorption is favored by increasing Cr(VI) initial concentration and adsorbent dosage. The studies of reaction kinetics and adsorption equilibrium showed that the experimental data were better fitted to the Pseudo-second-order and Langmuir isotherm models, establishing monolayer formation and chemisorption. The maximum adsorption capacity of CS/ Fe3O4 Nps was 440.75 mg/g, which indicates a high affinity of the adsorbent for Cr(VI). Finally, a kinetic diffusion study established that intraparticle diffusion, and in particular surface diffusion, are important resistances in the transport of Cr(VI) from the liquid phase to the active site.