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Electrochemical Analysis of Zirconiumin Aqueous and Organic Media

American Journal of Analytical Chemistry 2024年第2期15卷 99-118页

作者： Paul Mendy Démo Koita Theodore Tzedakis cheikhou kane Codou Guèye Mar-Diop Ecole Supérieure Polytechnique Université Cheikh Anta DIOP Dakar Sénégal Laboratoire de Génie Chimique Université de Toulouse III—Paul Sabatier Toulouse France

For the challenging nature of the zirconium environment analysis, this study consists to analyze the electrochemical behavior of Zirconium in both aqueous and organic media. To that end first the electrolytic media was selected on the basis of the Pourbaix potential-pH diagram, which provides informations on the predominance of Zr(IV) ion and Zr in aqueous media. In aqueous media, analyzes were first carried out in acidic media then in basic media. Studies have thus revealed that the acidic environment is not favourable for the electrochemical analysis of zirconium. Voltammograms obtained in an acidic environment show no zirconium detection signal;this is due to the strong presence of H+ ions in the solution. We have also observed in acidic media the phenomenon of passivation of the electrode surface. In aqueous alkaline media (pH = 13), we have drawn in reduction several Intensity-Potential curves by fixingsome technical parameterslike scanning speed, rotation speed of the electrode. The obtained voltammograms show cathodic waves, starting from -1.5 V/DHW and attributed to the reduction of Zr (IV) to Zr (0). The last phase of this study focused on the electrochemical analysis of zirconium in an organic media. In this media, several intensity-potential curves were plotted in reduction and in cyclic voltammetry with various parameters. Through several reduction analysis, the Zr (IV) was reduced to Zr (0) to the potential of -1.5 V/DHW. The electrochemical analysis of zirconium in organic media seems globally easier to achieve thanks to its large solvent window (i.e. dimethylformamide (DMF) solvent window > 6 V).

关键词： Zirconium Electrochemical Reduction Cyclic Voltammetry Voltammogram Dymethylformamide

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Influence of Variety and Maturity Level on Natural Convective Heat Drying of Four Onion Varieties Grown in Senegal

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Food and Nutrition Sciences 2018年第8期9卷 997-1013页

作者： Ngoné Fall Beye cheikhou kane Nicolas Cyrille Ayessou cheikhou Talla Abdou Sene Codou Mar Diop Laboratoire d’Electrochimie et de Procédés Membranaires (LEPM) ESP-UCAD Dakar Sénégal Centre d’Etudes sur la Sécurité alimentaire et les Molécules fonctionnelles (CESAM-RESCIF) ESP-UCAD Dakar Sénégal Laboratoire des Sciences Biologiques Agronomiques et de Modélisation des Systèmes Complexes (LaBAM)/UGB Saint-Louis Sénégal Institut Pasteur de Dakar Unité d’épidémiologie des maladies infectieuses Dakar Sénégal

The considerable post-harvest losses (5% to 40% depending on storage time) due to the high water content level of the onion varieties in Senegal are the main cause of the problem of access to local onion all year round. Therefore, drying is one of the techniques that can be used to solve the problem of onion perishability. This study deals with the characterization of naturally convective kinetics drying of four onion varieties in relation to their maturity level. The experiment was carried out using the gravimetric method. The Welch and Turkey statistical tests display a significant difference between the effective diffusivity coefficients depending on the maturity level within each variety and across the four varieties. The effective diffusivity coefficients of the Galmi Violet, Safari, Gandiol F1 and Orient F1varieties range from 2.18 × 10−11 ± 2.69 × 10−12 to 1.32 × 10−10 ± 1.17 × 10−11 m2⋅s−1 at a maturity level less than 80%. When the maturity level is greater than 85%, the effective diffusivity coefficients range from 1.30 × 10−11 ± 1.24 × 10−12 to 8.05 × 10−11 ± 8.94 × 10−13 m2⋅s−1. As far as the activation energy is concerned, the study only reveals a significant difference between the varieties whatever the maturity level is. The Galmi Violet variety stands out with an average activation energy of 66.71 ± 0.12 KJ⋅mol−1 K−1 for the maturity level below 80% and 58.74 ± 0.11 KJ⋅mol−1 for the maturity level above 85%. For the three remaining varieties, the average activation energy ranges from 58.15 ± 0.19 to 59.12 ± 0.13 KJ⋅mol−1 for a maturity level less than 80% whereas the rates go from 47.63 ± 0.28 to 49.96 ± 0.77 KJ⋅mol−1 when the maturity level is greater than 85%. In summary, the higher the maturity level is, the lower the effective diffusivity coefficients will be. The same tendency was observed with the activation energy. The Galmi

关键词： Allium cepa L. Drying Kinetics Maturity Level Effective Diffusivity

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Removal of Methyl Violet in Aqueous Solution on Activated Carbon Based on Saba senegalensis Shell Residues

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Journal of Geoscience and Environment Protection 2023年第5期11卷 197-208页

作者： Mouhamed Ndoye Mamadou Faye cheikhou kane Adama Diop Mar Codou Guèye Diop Water Energy Environment and Industrial Processes Laboratory Ecole Superieure Polytechnique (ESP) Dakar Senegal Cheikh Anta Diop University Dakar Senegal

Adsorption on activated carbon is one of the most widely used methods for the removal of dyes. The objective of this study is to valorize the shells of Saba senegalensis from local product in Senegal in the form of activated carbon and to test its effectiveness for the removal of methyl violet. The study was carried out in batch mode for a maximum duration of one hour with 100 mL of solution treated at 600 rpm. The results reveal that the granulometry 500 μm gives the best yield with an adsorption rate of 95%, a mass of adsorbent of 0.2 g gives an adsorption capacity of 20 mg/g, the contact time of one hour with a capacity of 5 mg/g. The study also showed that the adsorption process of methyl violet is described by the pseudo-second order kinetic model with correlation coefficient of 0.99. Two adsorption isotherms were studied, and the results revealed that the Freundlich model better describes the adsorption of methyl violet on Saba senegalensis shell residue-based activated carbon (SSSRAC). The results indicate that SSSRAC could be used as a low-cost alternative for the removal of textile dyes such as methyl violet.

关键词： Methyl Violet Adsorption Activated Carbon Saba senegalensis Shell

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Process Optimization and Modeling by Response Surface Methodology of Nitrite Electro-Reduction by Ti/RuO₂ + IrO₂ Electrode

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American Journal of Analytical Chemistry 2023年第12期14卷 531-540页

作者： Mar Bassine Boye Abdou Khadre Djily Dimé Adama Diop cheikhou kane Modou Fall Département de Chimie UFR SATIC Equipe des Matériaux Electrochimie et Photochimie Analytiques (EMEPA) de l’Université Alioune Diop de Bambey Bambey Sénégal Laboratoire d’Electrochimie et de Procédés Membranaires (LEPM) Ecole Supérieure Polytechnique de Dakar Dakar Sénégal Laboratoire de Chimie Physique Organique et d’Analyses Environnementales Université Cheikh Anta Diop de Dakar Dakar Sénégal

Electrochemical reduction is one of the most suitable methods for the treatment of highly nitrate-contaminated solutions. This work focuses on the optimization of parameters influencing the electrochemical denitrification of water by the Ti/RuO2 + IrO2 electrode. The methodological approach used consists in carrying out a series of electrolysis by scrutinizing the reaction selectivity according to the experimental conditions. For this study, the ions concentrations before and after electrolysis were determined by UV-vis absorption spectroscopy. The results of the process optimization showed that the electrochemical reduction ofis efficient at neutral pH after 120 mn of electrolysis at -100 mA. In contrast to works found in the literature, this study highlighted the process modeling that could open interesting perspectives to develop new treatment methods of polluted waters.

关键词： Electrochemical Reduction Water Treatment Nitrite Optimization Modelling

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Monitoring of Anthocyanins and Colour in Electrochemically Processed <i>Hibiscus sabdariffa</i>Juice

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Food and Nutrition Sciences 2021年第11期12卷 1073-1087页

作者： Khady Ndiaye cheikhou kane Omar Ben Khatab Cisse Nicolas Ayessou Codou Mar Diop Laboratoire d’électrochimie et des Procédés Membranaires ESP/UCAD Dakar Sénégal Laboratoire de Formation Continue en Industrie Agroalimentaire ESP/UCAD Dakar Sénégal

The vital role of anthocyanins in Hibiscus sabdariffa L. is now known to most consumers. The richness of anthocyanins in antioxidants, vitamin C, minerals, etc., provides Hibiscus juice with proven nutritional qualities. The health requirements of recent years have made food products with added preservatives or processed at high temperatures less popular, thus explaining the new orientations towards innovative and interdisciplinary technologies. Anthocyanins from Hibiscus sabdariffa L. are, however, sensitive to degradation factors such as temperature, light, enzymes and also oxygen. The instability of anthocyanins has long been a subject of research using classic techniques such as heat treatment, the results of which are often limited by the rapid degradation and above all the destruction of the nutritional and organoleptic qualities of the product. Oxygen dissolved in juices is so far treated by bubbling with an inert gas or by adding other molecules such as preservatives which can cause a lot of health damage. The electrochemical approach is a new stabilisation technique that reduces the dissolved oxygen in the juice, cold and without the addition of other molecules. The electrolysis of Hibiscus juice was carried out by noble electrodes (Platinum and Stainless Steel) with a well-characterised Time/Potential or Time/Intensity couple. The electroreduced samples and the control were then stored at 4°C, 25°C and 37°C for more than 6 months. Monitoring of anthocyanins in the first month, of the samples and the control, showed a significant difference of 10% between the electroreduced extract and the untreated control at 37°C, which had previously been problematic for the heat treatment and even for the other membrane techniques. Oxygen reduction on the platinum electrode/ECS allowed the retention of more than 10% of anthocyanins after 4 weeks of storage at 25°C and 37°C. At 4°C, a sign

关键词： Monitoring Anthocyanin Colour Oxygen Stabilisation Electrochemical Nafion Membrane Ratio

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Determination of Lead in Water by Linear Sweep Anodic Stripping Voltammetry (LSASV) at Unmodified Carbon Paste Electrode: Optimization of Operating Parameters

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American Journal of Analytical Chemistry 2018年第3期9卷 171-186页

作者： Ndoye Mouhamed kane cheikhou Gadji Elhadji Momar Rokhy Diédhiou Moussa Bagha Mar-Diop Codou Guèye Theo Tzedakis Ecole Supérieure Polytechnique Université Cheikh Anta Diop Dakar Senegal Laboratoire de Génie Chimique UMR CNRS 5503 Université de Toulouse III-Paul Sabatier Toulouse France

This study presents the elaboration of a simple and cheap electrode made by carbon paste introduced into a cavity of electrode body, and used for the lead traces determination in tap water. A potentiostatic pre-electrolysis at constant voltage enables the reduction of the lead (Pb2+) and the accumulation of the metallic lead at and into the carbon paste;the reoxidation of the Pb (Linear sweep voltammetry) leads to the anodic striping peak. The effect of the main operating parameters on the shape of the peak and the magnitude of the current was examined and their optimal values were determined. Then calibration was achieved and the method was successfully applied (using all the optimized parameters) to the determination of lead in water, with a detection limit of 0.138 μg·L-1. Compared to other methods (ICP-AES for example), the proposed method offers a satisfactory detection limit of the Pb2+ (0.138 μg·L-1) because of the important specific area of the carbon paste electrode, for a significantly lower cost. Besides, there is no observed loss in the electrode answer in terms of peak current, which means that there is no any irreversible steps nor deactivation of the electrode, even after ten successive measurements;only reduction of the lead followed by the deposit oxidation was observed at the electrode.

关键词： Carbon Paste Electrode Lead Linear Sweep Anodic Stripping Voltammetry Water

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