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Étude prospective pour la récupération par voie électrochimique en milieu solvant eutectique profond de l’or et de l’argent issus du traitement des cartes électroniques de téléphones portables
No full textThe mining of gold and silver is no longer sufficient to meet the growing demands of modern society, due to the depletion of resources and increasing requirements in sectors such as electronics and renewable energies. This calls for the search for sustainable solutions. Recycling cell phone circuit boards is an interesting option for recovering these precious metals. This thesis is part of the ANR-funded EE4Precious project, which aims to develop an innovative method combining electroleaching and electrodeposition reactions to extract gold and silver in an environmental-friendly way, using deep eutectic solvents (DES). The aim is to obtain pure metal phases at the cathode (selectivity), and to carry out both reactions with maximum faradic yield to enable DES recycling. Ethaline 1:2, a mixture of choline chloride (ChCl) and ethylene glycol (EG), was chosen as the reference DES. Subsequently, the substitution of EG by propylene glycol (PG) leading to a new DES named propeline, was explored. Several stages were envisaged to bring this project to fruition. Initially, since the performance of an electrochemical process depends on the electrolyte used, experiments focused on the physicochemical properties of ethaline and propeline: viscosity, conductivity, density and electroactivity range. The influence of water content on these properties was studied. By increasing the temperature and decreasing the ChCl:glycol ratio to 1:3, propeline exhibits comparable physico-chemical properties to 1:2 ethaline. Then the work switched to an in-depth study of the electrochemical reactions of anodic dissolution and cathodic deposition of silver and gold. The performance of the two DES for the electrochemical leaching of gold and silver was evaluated using pure metal phases. The efficiency of this step was determined after thorough development of analytical procedures dedicated to elemental analysis in DES media (ICP-OES). Thanks to the high complexing activity of these solvents, the electro-leaching step is efficient, with yields close to 100%, showing that PG is a good alternative to EG for the electrochemical process. Speciation of leached gold was determined by UV-visible spectrophotometry and EXAFS/XANES. Finally, the kinetic parameters of charge transfer and material transport at the electrode were determined. To obtain highly accurate and reliable values, several electrochemical methods and laws were used. The diffusion coefficients of gold and silver were determined by applying Cottrell and Levich's laws to data obtained by chronoamperometry in natural and convective diffusion regimes. The charge transfer coefficient α, the rate constant k0 and the diffusion coefficient were estimated from cyclic voltammograms (CV) using a model programmed in Matlab. The electroplating step was studied in a final section. Coupling tests between electroleaching and electrodeposition using a synthetic silver solution showed very encouraging potential, with faradic yields of around 100% for both stages, in a controlled atmosphere. Finally, following an initial CV study of bimetallic Au-Ag solutions, initial tests of selective gold deposition in potentiostatic mode have proved promising.L'extraction minière de l'or et de l'argent ne suffit plus à répondre à la demande croissante de notre société moderne, en raison de l'épuisement des ressources et de l'augmentation des besoins dans des secteurs comme l'électronique et les énergies renouvelables. Cela rend nécessaire la recherche de solutions durables. Le recyclage des cartes électroniques de téléphones portables est une option intéressante pour récupérer ces métaux précieux. Ce travail de thèse s'inscrit dans le projet EE4Precious financé par l'ANR, dont l'objectif est de développer une méthode innovante combinant électrolixiviation et électrodéposition pour extraire l'or et l'argent de manière respectueuse de l'environnement, en utilisant des solvants eutectiques profonds (DES). L'objectif est d'obtenir des phases métalliques pures à la cathode (sélectivité) et de mettre en œuvre les deux réactions avec un rendement faradique maximal afin de permettre le recyclage des DES. L'éthaline 1:2, mélange de chlorure de choline (ChCl) et d'éthylène glycol (EG), a été choisi comme DES de référence. Par la suite, la substitution de l'EG par du propylène glycol (PG), conduisant à un nouveau DES nommé propeline, a été explorée. Plusieurs étapes ont été envisagées pour mener à bien ce projet. Dans un premier temps, puisque les performances d'un processus électrochimique dépendent de l'électrolyte utilisé, les expériences se sont focalisées sur les propriétés physico-chimiques de l'éthaline et de la propeline : viscosité, conductivité, densité et domaine d'électro-activité. L'influence de la teneur en eau sur ces propriétés a fait l'objet d'une étude approfondie. L'augmentation de la température et la diminution de la proportion ChCl:glycol à 1:3 permet d'atteindre avec la propeline des propriétés physico-chimiques similaires à celles de l'éthaline 1:2. Le travail s'est ensuite porté sur l'étude approfondie des réactions électrochimiques de dissolution anodique et de dépôt cathodique de l'argent et de l'or. Les performances des deux DES pour la lixiviation électrochimique de l'or et de l'argent ont été évaluées à partir des phases métalliques pures. L'efficacité de cette étape a pu être déterminée après un développement approfondi des procédures analytiques dédiées à l'analyse élémentaire en milieu DES (ICP-OES). Grâce à la forte activité complexante de ces solvants, l'étape d'électrolixiviation est efficace, avec des rendements proches de 100 %, montrant que le PG est une bonne alternative à l'EG pour le processus électrochimique. La spéciation de l'or lixivié a été déterminée par spectrophotométrie UV-visible et EXAFS/XANES. Enfin, la détermination des paramètres cinétiques de transfert de charge et de transport de matière à l'électrode a été menée. Afin d'obtenir des valeurs d'une haute précision et fiabilité, plusieurs méthodes et lois électrochimiques ont été utilisées. Les coefficients de diffusion de l'or et de l'argent ont été déterminés en appliquant les lois de Cottrell et Levich sur les données obtenues par chronoampérométrie en régimes de diffusion naturelle et convective. Le coefficient de transfert de charge α, la constante de vitesse k0 et le coefficient de diffusion ont été estimés à partir de voltampérogrammes cycliques (CV) au moyen d'un modèle programmé sous Matlab. L'étape d'électrodéposition a été étudiée dans une dernière partie. Des tests de couplage entre électrolixiviation et électrodéposition effectuée à partir d'une solution synthétique d'argent montrent des résultats prometteurs affichant un rendement faradique d'environ 100 % pour les deux étapes, en atmosphère contrôlée. Enfin, après une première étude par CV de solutions bimétalliques Au-Ag, des premiers tests de dépôt sélectif d'or en mode potentiostatique ont été menés, qui se sont révélés prometteurs
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
Author Under Sail The Imagination of Jack London, 1893-1902
No full textIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Intro -- Title Page -- Copyright Page -- Dedication -- Contents -- Acknowledgments -- Introduction -- 1. Spirit Truth -- 2. From Absorption to Theatricality and Back Again -- 3. "I Will Build a New Present" -- 4. Sons as Authors -- 5. Fathers as Publishers -- 6. The Daughter as Author -- 7. Lovers as Authors -- 8. At Sea with the Family -- 9. Yellow News, Yellow Stories -- 10. The Return Home -- Notes -- Bibliography -- Index -- About Jay WilliamsIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Description based on publisher supplied metadata and other sources.Electronic reproduction. Ann Arbor, Michigan : ProQuest Ebook Central, YYYY. Available via World Wide Web. Access may be limited to ProQuest Ebook Central affiliated libraries
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