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Estrogen removal through adsorption using carbon materials prepared from biomass waste
No full textEndocrine disruptors are class of micropollutants that can influence and deregulate the endocrine system in humans and animals. Endocrine disruptors can consist of natural estrogenic hormones, such as E1 and E2, and synthetic estrogenic hormones, such as EE2, that are not easily removed by conventional treatment processes in water and sewage treatment plants, becoming dangerous emerging pollutants. This work addresses the removal of such compounds from aqueous matrices through adsorption processes onto activated carbon produced from biomass waste.
The materials selected were almond shell in natura (ASiN) and cork in natura (CiN). These were activated through carbonization at 550ºC for 1 h, obtaining carbonized almond shell (CAS) and carbonized cork (CC). These materials were characterized by carbonization yield, moisture and ash content, PZC value, quantification of acidic and basic sites and FTIR analysis.
For the adsorption assays, the impact of conditions such as adsorbent type, temperature and medium pH was assessed in relation to removal performance. Kinetic and isotherm assays were also performed in batch mode, together with the assessment of the thermodynamic data.
The results show that equilibrium time was 16 h for ASiN, 4 h for CAS, 6 h for CiN and 24 h for CC. The adsorption process was regulated through the Elovich model for all adsorbents except for CiN, where the best model was PSO. Moreover, cork-based adsorbents presented higher adsorption capacities and activation through carbonization did not contribute to an increase in estrogen removal. Therefore, CiN was selected as the best material for estrogen removal to the posterior assays.
A temperature increase did not affect CiN’s adsorption capacity, and Ea was determined to be 136.15, 80.84 and 146.81 kJ/mol for E2, EE2 and E1, respectively. Moreover, pH change only negatively affects adsorption when in extreme basic media.
CiN’s adsorption process has been characterized by the Sheindorf-Rebuhn-Sheintuch multicomponent isotherm for all estrogens, with maximum adsorption capacities of 3.75, 7.23 and 3.82 mg/g achieved for estrogens E2, EE2 and E1, respectively, at 25ºC. Average removal percentage increased with the adsorbent’s dosage until it reached a maximum of 66.1% at 1 g/L. Both the adsorption capacity and removal percentage decreased with the increase in temperature.
Thermodynamic data was determined and negative values for ΔGº and ΔHº and positive values for ΔSº were obtained, meaning that adsorption was characterized as spontaneous, exothermic and entropically favourable. It was verified that estrogen adsorption occurred through a combination of
chemisorption and physisorption phenomena. Chemisorption occurred mainly through pEDA interactions and hydrogen bridges between estrogen and CiN’s functional groups and aromatic rings, while physisorption occurred mainly through pore filling. pEDA bonding assisted by hydrophobic interactions could be an explanation for the higher adsorption rates verified for EE2 in CiN.Disruptores endócrinos constituem uma classe de micropoluentes capazes de interferir e desregular o funcionamento fisiológico do sistema endócrino em organismos humanos e animais. Entre esses compostos destacam-se as hormonas estrogénicas naturais, como a estrona (E1) e o 17β-estradiol (E2), bem como a hormona estrogénica sintética 17α-etinilestradiol (EE2). Tais compostos apresentam elevada persistência no ambiente aquático, uma vez que não são eficientemente removidos por processos convencionais de tratamento de água e efluentes, sendo, por isso, classificados como poluentes emergentes. O presente trabalho aborda a remoção de tais substâncias de matrizes aquosas por meio de processos de adsorção em carvão ativado produzido a partir de resíduos de biomassa.
A biomassa selecionada para a produção dos adsorventes consistiu na casca de amêndoa in natura (ASiN) e cortiça in natura (CiN). Estes materiais foram ativados através de carbonização a 550ºC por 1 h, obtendo-se casca de amêndoa carbonizada (CAS) e cortiça carbonizada (CC), sendo posteriormente caracterizados através do rendimento de carbonização, teor de humidade e cinzas, valor de pHPZC, quantificação de sítios ácidos e básicos e análise de grupos funcionais por FTIR.
Nos ensaios de adsorção, avaliou-se o impacto de parâmetros operacionais como tipo de adsorvente, temperatura e pH do meio sobre a eficiência de remoção dos estrogénios. Os estudos cinéticos e de isotérmicas foram conduzidos em modo de batelada, tendo permitido a determinação de dados termodinâmicos.
Os resultados obtidos mostram que o tempo de equilíbrio foi de 16 h para ASiN, 4 h para CAS, 6 h para CiN e 24 h para CC. O processo de adsorção segue o modelo de Elovich para todos os adsorventes, exceto para o CiN, em que o modelo de pseudo-primeira ordem (PSO) é mais adequado. Além disso, os adsorventes baseados em cortiça apresentaram capacidades de adsorção superiores e o processo de carbonização não contribuiu para um aumento na remoção de estrogénio. Desta forma, verifica-se que, dos adsorventes estudados, CiN é o melhor material para a remoção de estrogénio e foi utilizado para os ensaios posteriores.
No que se refere ao parâmetro temperatura, verifica-se que o seu aumento não afeta significativamente a capacidade de adsorção do CiN. Os valores da energia de ativação, Ea, obtidos para a remoção de E2, EE2 e E1 são 136,15, 80,84 e 146,81 kJ/mol, respetivamente. A análise do pH mostra que condições extremamente alcalinas têm uma influência negativa no processo de adsorção.
O processo de adsorção do CiN foi descrito pela isotérmica multicomponente Sheindorf-Rebuhn-Sheintuch para todos os estrogénios, com capacidades máximas de adsorção, a 25ºC, de 3,75, 7,23 e 3,82 mg/g atingidas para os estrogénios E2, EE2 e E1, respetivamente. A percentagem média de remoção aumentou com a dose de adsorvente, atingindo um valor máximo de 66,1% a 1 g/L. As capacidades de adsorção e remoção percentual diminuíram com o aumento da temperatura.
Os parâmetros termodinâmicos, ΔGº e ΔHº negativos e ΔSº positivo, indicam que o processo de adsorção é espontâneo, exotérmico e entropicamente favorável. Verifica-se também que a adsorção de EE2 ocorreu predominantemente através de quimissorção, enquanto a adsorção de E1 e E2 ocorreu através de uma combinação de processos de quimissorção e fisissorção. A quimissorção ocorreu principalmente através de interações pEDA e pontes de hidrogénio entre os grupos funcionais e anéis aromáticos do estrogénio e do CiN, enquanto a fisissorção se deu principalmente através de enchimento dos poros que constituem a estrutura do adsorvente
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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