Browsing by Author "Espinoza-Montero, Patricio Javier"
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Item Open Access A nafion film cover to enhance the analytical performance of the CuO/Cu electrochemical sensor for determination of chemical oxygen demand(2019-02) Espinoza-Montero, Patricio Javier; Fernández Martínez, Lenys Mercedes; Espinoza-Montero, Patricio Javier y Fernández Martínez, Lenys MercedesWe modified and evaluated the performance of a CuO/Cu electrochemical electrode for chemical oxygen demand (COD) determination by covering it with a Nafion (Nf) film. The resulting modified CuONf/Cu electrode sensor was used for the electrochemical determination of COD in river, slaughterhouse and estuarine water samples in order to evaluate its performance for this particular task. It was compared with the CuO/Cu sensor with no Nafion. The main electrochemical characteristics of interest, resistance, sensitivity, accuracy and reproducibility, were assessed by means of Linear Sweep Voltammetry using glucose as a standard. Results of these essays indicate that the procedure used produced smooth and firmly attached Nf films covering the whole copper surface. This sensor was shown to be resistant to interferences and effective in electro-oxidation of a wide range of organic compounds and therefore very useful for COD determination. Using the newly developed CuONf/Cu electrode an analytical linear range of 50 to 1000 mg·L−1 COD, with a detectionlimitof2.11mg·L−1 (n=6)CODwasachieved. The comparison shows that theCuONf/Cu sensor is more appropriate for COD determination than its counterpart with no Nafion.Item Open Access Analysis of Ag(I) biocide in water samples using anodic stripping voltammetry with a boron-doped diamond disk electrode(2018-05-14) Espinoza-Montero, Patricio Javier; Espinoza Montero, Patricio JavierThe electroanalytical performance of a new commercial borondoped diamond disk and a traditional nanocrystalline thin-film electrode were compared for the anodic stripping voltammetric determination of Ag(I). The diamond disk electrode is more flexible than the planar film as the former is compatible with most electrochemical cell designs including those incorporating magnetic stirring. Additionally, mechanical polishing and surface cleaning are simpler to execute. Differential pulse anodic stripping voltammetry (DPASV) was used to detect Ag(I) in standard solutions after optimization of the deposition potential, deposition time and scan rate. The optimized conditions were used to determine the concentration of Ag(I) in a NASA simulated potable water sample and a NIST standard reference solution. The electrochemical results were validated by ICP-OES measurements of the same solutions. The detection figures of merit for the disk electrode were as good or superior to those for the thin-film electrode. Detection limits were ≤5 μgL −1 (S/N = 3) for a 120 s deposition period, and response variabilities were <5% RSD. The polished disk electrode presented a more limited linear dynamic range presumably because of the reduced surface area available for metal phase formation. The concentrations of Ag(I) in the two water samples, as determined by DPASV, were in good agreement with the concentrations determined by ICP-OES.Item Metadata only Applicability of goethite/reduced graphene oxide nanocomposites to remove lead from wastewater(2019-11-07) Espinoza-Montero, Patricio Javier; Espinoza Montero, Patricio JavierLead ion in drinking water is one of the most dangerous metals. It affects several systems, such as the nervous, gastrointestinal, reproductive, renal, and cardiovascular systems. Adsorption process is used as a technology that can solve this problem through suitable composites. The adsorption of lead (Pb(II)) on graphene oxide (GO) and on two goethite (α-FeOOH)/reduced graphene oxide (rGO) composites (composite 1: 0.10 g GO: 22.22 g α-FeOOH and composite 2: 0.10 g GO: 5.56 g α-FeOOH), in aqueous medium, was studied. The GO was synthesized from a commercial pencil lead. Composites 1 and 2 were prepared from GO and ferrous sulfate. The GO and both composites were characterized by using scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM), Raman spectroscopy, X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and dynamic light scattering (DLS). The adsorption capacity of Pb(II) on the GO and both composites was evaluated through adsorption isotherms. Composite 1 presented a significant agglomeration of α-FeOOH nanorods on the reduced graphene oxide layers. Meanwhile, composite 2 exhibited a more uniform distribution of nanorods. The adsorption of Pb(II) on the three adsorbents fits the Langmuir isotherm, with an adsorption capacity of 277.78 mg/g for composite 2200 mg/g for GO and 138.89 mg/g for composite 1. Composite 2 emerged as a highly efficient alternative to purify water contaminated with Pb(II).Item Metadata only Correlación analítica-técnica entre ensayos de laboratorio de módulo resiliente y California bearing ratio de la mina Copeto(2020-01) Cando Tipan, Wilson Oswaldo; Espinoza-Montero, Patricio Javier; Fernández Martínez, Lenys Mercedes; Espinoza Montero, Patricio JavierSe reporta una correlación analítica-técnica entre ensayos de laboratorio de Módulo Resiliente y California Bearing Ratio, para un agregado que proviene de la mina de Copeto (Toachi – Santo Domingo de Los Tsáchilas-Ecuador), la cual arroja valores reales útiles en la optimización del material utilizado en proyectos viales, a través de la obtención del Módulo Resiliente. El estudio se sustenta en la cualificación de la mina, mediante ensayos fisicoquímicos, que permite conocer las características propias de los agregados, según las normas ASTM. Con el logro de una correlación entre el CBR y el Módulo Resiliente real de la mina en estudio, se tiene valores reales en el comportamiento de los materiales, que se van a usar en la estructura de la vía, lo que genera como resultado espesores de capas menores, que, al momento de la construcción reduce el tiempo de entrega, la cantidad de material y por consiguiente el costo final de la construcción de la vía.