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Ciudad Madero, Mexico

Saucedo-Rivalcoba V.,National Autonomous University of Mexico | Martinez-Hernandez A.L.,National Autonomous University of Mexico | Martinez-Barrera G.,National Autonomous University of Mexico | Velasco-Santos C.,Queretaro Institute of Technology | And 2 more authors.
Water, Air, and Soil Pollution

The feasibility of employing a porous polyurethane-keratin hybrid membrane for the removal of hexavalent chromium was investigated. Keratin was extracted from chicken feathers and incorporated onto a synthetic polyurethane polymer to synthesize a hybrid membrane. Keratin supply active sites to bioadsorb Cr (VI) and polyurethane play an important role as the support to protein. Also, polyurethane-keratin biofiber membranes were synthesized. Biofibers obtained from chicken feathers were modified to activate their surface. The effective pore in membranes is less than 50 nm, which places these materials in the mesopore range. Scanning electron microscopy (SEM) was used to study the morphology of membranes, and mechanical dynamical analysis (DMA) was used to evaluate the viscoelastic properties. NH, C=O, S-S and C-S were determined via Fourier-transform infrared (FTIR) analysis as functional groups of keratin, which participate in the linking sorption of hexavalent chromium. Adsorption of Cr(VI) was carried out in a filtering system at low contact time in continuous flux; the maximum removal reached was 38% at neutral pH of chromium solution. Results indicate that the isoelectric point of keratin is relevant in the adsorption process. pH of keratin solution above the isoelectric point brings about higher adsorption of heavy metals, whereas lower pH causes minor adsorptions, due to the functional groups' ion charges. Based on the results, keratin extracted from feathers is a natural biosorbent that can be incorporated onto synthetic polymers to develop novel membranes and improve its applications in the heavy metal separation process. © Springer Science+Business Media B.V. 2010. Source

Paramo-Garcia U.,Metropolitan Autonomous University | Paramo-Garcia U.,Instituto Tecnologico Of Cd Madero | Ibanez J.G.,Ibero-American University of Mexico | Batina N.,Metropolitan Autonomous University
International Journal of Electrochemical Science

The tailoring of key characteristics of conducting polymers (e.g., thickness, conductivity, degree of oxidation, color and morphology) is desirable for specific applications. We present results on the regulation of the thickness of polypyrrole films electrochemically grown on glassy carbon by potentiodynamic and potentiostatic techniques at circumneutral pH in the presence of selected aqueous dopant anions (i.e., I -, NO 3 -, Br -, Cl -, ClO 4 -, SO4 2 - and F -). In this manner, a supporting electrolyte containing KI yields relatively thick and highly conductive films whereas KF produces little conductive, very thin films. Other electrosynthesis parameters (i.e., applied potential range, number of cycles, time) also play a key role. For example, one can obtain insulating films by applying potentials in the region required for overoxidation of the film. © 2011 by ESG. Source

Brachetti-Sibaja S.B.,Altamira | Brachetti-Sibaja S.B.,Instituto Tecnologico Of Cd Madero | Dominguez-Crespo M.A.,Altamira | Rodil S.E.,National Autonomous University of Mexico | Torres-Huerta A.M.,Altamira
Journal of Alloys and Compounds

Cerium and lanthanum coatings were deposited on glass, silicon (1 0 0), and aluminum alloy by RF magnetron sputtering in which several experimental conditions such as power, substrate temperature, and deposition time were varied, using pure CeO2 and La2O3 targets. The effect of deposition parameters on the bonding structure, surface morphology and properties against corrosion of rare earth (RE) coatings formed on metallic substrate was reported. The microstructure and chemistry of the thin film were characterized by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), and X-ray photoelectron spectroscopy (XPS); whereas their use as corrosion resistant coatings was studied in aqueous NaCl solution (3.0 wt%) by using polarization curves. Variations in these properties were observed by increasing the substrate temperature which modifies the crystallinity of the rare earth coatings. XRD and XPS findings indicate that the cerium coatings are composed by CeO2 and a significant quantity of Ce2O3 due to oxygen deficiency in the sputtering chamber, whereas La2O3/La(OH)3 and some La intermetallic compounds are detected in the lanthanum films. Variations in the Ecorr and Icorr were found as a function of the thickness, texture, and morphology of the as-prepared coatings. © 2014 Elsevier B.V. All rights reserved. Source

Lujan-Acosta R.,Research Center en Quimica Aplicada | Sanchez-Valdes S.,Research Center en Quimica Aplicada | Ramirez-Vargas E.,Research Center en Quimica Aplicada | Ramos-DeValle L.F.,Research Center en Quimica Aplicada | And 4 more authors.
Materials Chemistry and Physics

The synergistic effect of organo-modified montmorillonite (Nanomer I28E and Cloisite 20A) and metal hydroxides (magnesium hydroxide MH and alumina trihydrate ATH) as flame retardants in LDPE/EVA nanocomposites compatibilized with amino alcohol grafted polyethylene (PEgDMAE) was studied. Morphological characterization of nanocomposites was carried out by means of X-ray diffraction (XRD) and scanning transmission electron microscopy (STEM). Flame-retardant properties of nanocomposites were evaluated by the UL-94 horizontal burning and cone calorimeter tests and limiting oxygen index (LOI). Thermal degradation behavior was analyzed with a Fourier transform infrared coupled with the thermogravimetric analyzer (TG-FTIR). The XRD analysis showed a displacement of the d001 plane characteristic peak of clay to lower angles, which indicates an intercalated-exfoliated morphology. From STEM images it was observed a good dispersion of flame retardants (MH and ATH) throughout the polymer matrix which was reflected in flame-retardant properties. TG-FTIR showed a better thermal stability of nanocomposites and the gases evolved during combustion showed an important reduction. Based on thermal stability and thermal degradation results, the flame-retardant mechanism of LDPE/PEgDMAE/EVA/Clay/MH nanocomposites was proposed. © 2014 Elsevier B.V. All rights reserved. Source

Lozano T.,Autonomous University of Tamaulipas | Laria J.,Autonomous University of Tamaulipas | Lafleur P.G.,Ecole Polytechnique de Montreal | Sanchez-Valdes S.,Research Center en Quimica Aplicada | And 2 more authors.
Polymer Engineering and Science

The β-phase in polypropylene (PP) induced by shear rate in a single-screw extruder was studied. PP samples were extruded with and without a breaker plate at the exit of the extruder at five different screw rotational speeds: 20, 40, 60, 80, and 100 rpm. Differential scanning calorimeter was used to observe the melting behavior of the samples. The β-phase was quantified by wide angle X-ray diffraction. Extruded samples with a breaker plate showed higher values of β-phase of PP than those extruded without a breaker plate. With a breaker plate, the maximum percentage of β-phase was observed at 60 rpm (19.9%), whereas the maximum β-phase content without breaker plate was observed at 40 rpm (13.6%). The higher level of β-phase with the breaker plate was attributed to the shear rate induction and to the orientation by shear of the polymer chains through the orifices of the breaker plate. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers Copyright © 2012 Society of Plastics Engineers. Source

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