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Browsing by Author "Hormaza Anaguano, Angelina"

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    Estandarización de la difenilcarbazida como indicador y acomplejante en la identificación de cromo hexavalente – Cr (VI)
    (Corporación Universitaria Lasallista, 2013) Doria Herrera, Gloria María; Paz Ordoñez, Paulo Andrés; Hormaza Anaguano, Angelina
    Introduction. The treatment of water polluted with metals has gained a great importance in history, as the presence of such water not only generates a nasty visual impact, but also affects the ecosystems. One of the most toxic and stable metals in solution is Cr (VI). Its identification and quantification are very important, and so is its removal. Among the analysis techniques, colorimetry is one of the most economic and efficient to identify this metallic ion in solution, thanks to the action of the 1,5-diphenylcarbazid, which allows an exact determination of its presence in solution. Objective. To establish the best conditions to implement 1,5- diphenylcarbazid as a complexity agent to determine Cr (VI) in solution. materials and methods. The best work conditions were assessed by elaborating the calibration curves, identification of extinction coefficients, effect of the dissolvent, detection-quantification limit and degradation kinetics, after the action of the complexity agent. The determinations were performed with the UV- visible spectrophotometry technique. Results. The calibration curves obtained satisfactory results (99.11 %, 97.35 % and 99.17 %) with 95 % of confidence. The detection limit determined is 0.096 ppm and the quantification limit is 0.35 ppm. These results are very satisfactory, given the sensibility of the technique. The effect of the dissolvent with acetone, methanol and ethanol showed small batochromic displacements and a good correlation. Conclusion. 1,5-diphenylcarbazid is an adequate complexity agent to determine Cr (VI) in solution.
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    Estudio preliminar de la cascarilla de arroz modificada y su efecto en la adsorción de Cr(VI) en solución
    (Corporación Universitaria Lasallista, Editorial Lasallista., 2016) Doria Herrera, Gloria María; Valencia Uribe, Gloria Cristina; Hormaza Anaguano, Angelina; Gallego Suárez, Darío
    There are several studies that affirm that rice husk has a good adsorption capacity in an aqueous solution for removing Cr(VI). On the other hand, the Fenton reagent leads to the formation of hydroxyl radicals, considered as highly oxidant species, and this has brought their wide application in water treatments. Concerning the rice husk, a waste from agricultural industries, it is regarded as an environmental problem given its accumulation, but this waste contains a lot of lignin, cellulose, hemicellulose and silicon oxides and, therefore, it is an efficient natural adsorbent to remove heavy metals. The chemical modification of these materials ́ surfaces increases the adsorption capacity of metals in solutions.Objective. Determine the conditions for the modification reaction of rice husk with the Fenton reagent and establish the effect on the removal of Cr(VI) in aqueous solution before and after the modification.materials and methods. The effect of variables such as initial pH, [Fe+2]/[H2O2] ratio and time of the reactants were analyzed in order to establish the best conditions for the modification. Then, a 2k factorial analysis was performed with the initial metal concentration (C), acidity of the medium (pH) and adsorbent ́s dosage (D) variables, in order to establish the changes in terms of removal percentages.Results. It was demonstrated that with a lower dose of the contaminant (0.7 ppm), the removal percentages reached 90% in both the modified and the native husks.Conclusions.This research work demonstrated the structural modification of rice husk and the Fenton reagent and also demonstrated that, as the Cr(VI) is increased, the removal percentage is lower. Therefore, the Cr(VI) concentration is a significant variable in the metals ́ removal in a solution and, the other way around, the dose of the adsorbent in the ratio used is not a significant variable in the model obtained.