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Removal of lead (II) from aqueous solutions by adsorption onto activated carbons prepared from coconut shell
Full text linkIn the nuclear field, the availability of effective techniques to eliminate lead pollution from wastewater is of interest both for the purposes of radiation protection from the radioactive isotope lead-210 and also for the issues related to the use of lead in the new generation reactors nowadays under study. Evidences exist of lead pollution due to the radioactive isotope lead-210 in the proximities of uranium extraction mines. In this study, two commercial granular activated carbons obtained by physical activation of coconut shell, specifically developed and selected to purify potable water from dissolved organics (GCN 1240) and for use in gold recovery systems (GCN 816 G), were studied in batch systems to evaluate their effectiveness for separation of lead (II) from aqueous solutions. A characterization of the two carbons, different in particle size, is provided through determination of their pH(PZC) and scanning electron microscope analysis. Adsorption of lead (II) was observed as a function of contact time, and its kinetics were fitted. Adsorption data at equilibrium were fitted by isotherm models and the maximum adsorption capacity of the carbons resulted to be 92.39mg/g (GCN1240) and 32.08mg/g (GCN 816 G). Experiments were carried out to investigate effects of pH on lead adsorption, evidencing that best removal performances of lead occur near pH 5.0. The present study shows that the considered commercial granular activated carbons can be successfully adopted for removal of lead (II) by adsorption from aqueous solutions.
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Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Full text link“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
Full text linkWe 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
Prove batch di adsorbimento di piombo e uranio su carboni attivi commerciali ricavati da noci di cocco
No full textLAUREA SPECIALISTICANel presente lavoro di tesi, viene presentata un’indagine sperimentale inerente all’adsorbimento di piombo(II) e uranio(VI) su carboni attivi, quale tecnica di separazione di specie inquinanti da soluzioni acquose. L’attività sperimentale è stata condotta attraverso la realizzazione di prove batch in laboratorio. I test di adsorbimento hanno riguardato due carboni attivi commerciali attivati termicamente e derivati da gusci di noce di cocco, denominati GCN816 G e GCN1240, diversi per dimensione dei granuli. L’adsorbimento di piombo(II) è stato studiato misurando le capacità di adsorbimento per diversi tempi di contatto, al fine di esaminare la cinetica e di valutare il tempo di equilibrio; i dati sperimentali sono stati interpretati mediante modelli cinetici. Si è poi indagato l’effetto del pH sulle performance di adsorbimento: esse sono risultate fortemente influenzate da tale parametro, in quanto l’efficienza di separazione è apparsa alquanto inibita per pH molto acidi e prossima al 100% per pH superiori al valore in cui insorge precipitazione dell’idrossido di piombo; formazione di precipitato è stata osservata sulla superficie del carbone tramite microscopio elettronico a scansione (SEM). Successivamente è stata ricavata l’isoterma d’adsorbimento di piombo(II); il fit dei dati sperimentali ne ha consentito l’interpretazione tramite i modelli di Langmuir e Freundlich, i cui parametri hanno fornito informazioni quantitative sulle proprietà di adsorbimento nei confronti dell’inquinante in oggetto. Infine è stata posta attenzione a come l’adsorbimento sia influenzato dalla concentrazione iniziale di inquinante e dalla massa di carbone attivo disperso. Per quanto concerne l’adsorbimento di uranio(VI) su carboni attivi, sono stati svolti studi cinetici e studi all’equilibrio per ricavare l’isoterma di adsorbimento. Il processo è risultato fortemente influenzato dal pH della soluzione. I carboni attivi sottoposti a test si sono rivelati in grado di adsorbire piombo e uranio, mostrando, per talune associazioni carbone/contaminante, ottime capacità massime di adsorbimento.In this work of degree thesis, an experimental investigation about adsorption of lead(II) and uranium(VI) onto activated carbons is presented as a separation technique to remove pollutants from aqueous solutions. The experimental activity has been carried out by executing batch experiments in the laboratory system. The adsorption tests have regarded commercial activated carbons obtained from coconut shell, named GCN816 G and GCN1240, different in particle size. Adsorption of lead(II) has been studied by measuring the metal uptake at different contact times, in order to examine the kinetics and determine the equilibrium time; experimental data have been interpreted by kinetic models. Then, the effect of pH on adsorption has been investigated: it was strongly influenced by this parameter, in that the removal efficiency appeared highly inhibited at very acidic pHs and near to 100% around pHs major than the value at which precipitation of lead hydroxide occurs; formation of precipitate has been observed on the carbon surface with scanning electron microscope (SEM). Then, the adsorption isotherm of lead(II) has been obtained; fitting the experimental data, it has been possible to interpret it by the Langmuir and Freundlich models, the parameters of which provided quantitative information about the adsorption properties towards the pollutant. At last, attention has been given to how the adsorption is influenced by the initial concentration of pollutant and by the activated carbon dosage. About adsorption of uranium(VI) onto activated carbons, kinetic and equilibrium studies have been done, in order to get the adsorption isotherm. The process resulted strongly influenced by the pH of the solution. The tested activated carbons provided an effective removal of lead and uranium by adsorption, showing good maximum adsorption capacities
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe 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
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