We 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 detection limit of 2.11 mg·L−1 (n = 6) COD was achieved. The comparison shows that the CuONf/Cu sensor is more appropriate for COD determination than its counterpart with no Nafion.
The presence of antimony(III) in water represents a worldwide concern, mainly due to its high toxicity and carcinogenicity potential. It can be separated from water by the use of sustainable biopolymers such as chitosan or its derivatives. The present study applied chitosan modified with iron(III) beads to Sb(III) removal from aqueous solutions. The resulting material performed with a high adsorption capacity of 98.68 mg/g. Material characterization consisted of Raman spectroscopy (RS), X-ray diffraction (XRD), scanning electron microscope observations (SEM-EDX), Fourier transform infrared spectroscopy (FTIR) and point of zero charge (pHpzc). The adsorption study included pH study, effect of initial concentration, kinetics, ion effect, and reusability assessment. The RS, XRD, and FTIR results indicated that the main functional groups in the composite were related to hydroxyl and amino groups, and iron oxyhydroxide species of α-FeO(OH). The pHpzc was found to be 7.41. The best adsorption efficiency was set at pH 6. The equilibrium isotherms were better fitted with a non-linear Langmuir model, and the kinetics data were fitted with a pseudo-second order rate equation. The incorporation of iron into the chitosan matrix improved the Sb(III) uptake by 47.9%, compared with neat chitosan (CS). The material did not exhibit an impact in its performance in the presence of other ions, and it could be reused for up to three adsorption–desorption cycles.
La presente investigación trata sobre la validación del método de análisis in-situ de Cadmio y Plomo mediante Voltamperometría de Redisolución Anódica en agua de consumo humano, con la posibilidad de ser aplicado in situ. Los parámetros de validación fueron: incertidumbre, linealidad, sensibilidad, límite de detección y cuantificación, precisión y exactitud. Fue evaluado el método en dos rangos de trabajo. El coeficiente de repetibilidad para Cadmio en rango bajo fue del 10.4% y en el alto fue de 9.07%, mientras que en la reproducibilidad se obtuvo para el rango bajo 1.56% y en el rango alto fue de 0.10%, por su parte la exactitud obtenida como porcentaje de recuperación fue del 93 % para el rango bajo y del 117.75 % para el rango alto. En cuanto al coeficiente de repetibilidad de Plomo presentó en rango bajo de 7.13% y en el rango alto de 11.60%, y para la reproducibilidad en el rango bajo se obtuvo 0.02919% y para el rango alto 0.60%, por su parte, la exactitud para el caso del rango bajo en plomo fue de 91% mientras que 103.33% se obtuvo en el rango alto. La sensibilidad expresada como la pendiente de la curva de calibración para Cadmio fue de 1.14 µA.L/µg para el rango bajo y 0.7353 µA.L/µg para el rango alto, y para Plomo 1.10 µA.L/µg y 1.32 µA.L/µg en el rango bajo y alto respectivamente. Las muestras de agua potable evaluadas no presentaron presencia de Pb y Cd en el límite de detección del método.
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