1,720,961 research outputs found
Removal of heavy metals from water by capacitive deionization electrode materials derived from chicken feathers
Full text linkA Dissertation Submitted in Partial Fulfillment of the Requirements for the Degree of Master’s in Materials Science and Engineering at Nelson Mandela African Institution of Science and TechnologyCapacitive deionization (CDI) is an emerging desalination technology based on the principle of electrical double layer capacitors. When the voltage is applied to the surface of the electrodes, electrodes become oppositely charged and ions are adsorbed onto the electrode surfaces under the presence of the electric field, thus producing a purified stream of water. Once the electrodes are saturated with ions, adsorbed ions can desorb from the surface of the electrodes when the applied voltage is reversed or removed. Electrode materials play an important role in CDI performance. To date, the porous carbon derived from biomass shows a competitive advantage in CDI practical applications because of their low production costs, availability, good electrical conductivity, large specific surface areas, and environmental compatibility. In this study a high surface area porous carbons were synthesized from chicken feathers through pyrolysis and KOH activation; the KOH: CF ratio (R) and activation temperature (Ta) were variable parameters. The carbon samples synthesized were characterized by SEM, FTIR spectroscopy and nitrogen adsorption-desorption isotherms at 77 K and desalination experiments were performed by using potentiostat/galvanostat. All samples except the untreated carbon exhibited type IV isotherms demonstrating the existence of mesopores. The lead (Pb2+) removal test was performed with a CDI cell containing the fabricated carbon electrode and 100 mgL-1 Pb (NO3)2 solution; the sample prepared with the ratio R of 1:1 and Ta = 800 K exhibited higher Pb2+ removal efficiency of 81% and electro sorption capacity of 4.1 mgg-1 at the electrode potential 1.2 V and flow rate 5 mLmin-1. Therefore, chicken feather derived carbon (CF) is considered a promising CDI electrode material for the removal of heavy metals from wastewater
Metal oxides modified Carbon electrode materials for Fluoride and Paraquat removal from water by capacitive deionization
Full text linkA Thesis Submitted in Fulfilment of the Requirements for the Degree of Doctor of Philosophy in Materials Science and Engineering of the Nelson Mandela African Institution of Science and TechnologyCapacitive deionization (CDI) is an emerging water treatment technology with many
advantages, including low energy consumption, high efficiency, low cost, green and pollution free electrode regeneration. However, the electrode material is the main controlling factor for
achieving high CDI performance. For a long time, activated carbon (AC) has been a preferred
electrode material for CDI due to its availability, ease of preparation, low cost, and tunable
textural properties. However, the pristine AC lacks selectivity towards the targeted ions,
resulting in unnecessary energy consumption for treating polluted water and decreasing the
removal efficiency (RE) of the targeted pollutant. To improve ion selectivity, in this study,
composites of AC with metal oxides have been synthesized through a simple and one-step co precipitation method at ambient temperature (23-27°C) for defluoridation and removing
paraquat (PQ) from water. The composite properties were characterized by X-ray diffraction,
scanning electron microscopy, Fourier transform infrared spectroscopy, energy-dispersive X ray spectroscopy, and Brunauer-Emmett-Teller analysis. In competitive fluoride (Fˉ) removal
CDI experiments, AC–Al4Fe2.5Ti4 composite reduced the Fˉ concentration from 5.15 to 1.18
mg/L, below the allowable limit of 1.5 mg/L set by the World Health Organization while
pristine AC reduced the Fˉ concentration to 4.5 mg/L. Also, AC–Al4Fe2.5Ti4 composite
demonstrated a high RE of 79% and excellent regeneration performance after continuous
electric adsorption–desorption cycles. Furthermore, CDI batch experiments compared the
electrosorption of paraquat (PQ) herbicide by the composite electrodes (AC-Al2O3: 1:1) and
pristine AC. The performance of the composite electrodes showed that PQ RE and
electrosorption capacity (EC) depend on aluminium content loading, applied potential, flow
rate, and charging time. At 1.2 V, a flow rate of 15 mL/min, and a charging time of 3 h, the
composite electrode demonstrated a RE, EC, and energy consumption of 95.5%, 1.27 mg/g,
and 0.055 kWh/m3
, respectively, compared to 62%, 0.83 mg/g, and 0.11 kWh/m3
for the
pristine AC. The presence of other ions/pollutants was found to have negligible interference on
PQ pesticide removal as the RE of the AC/Al2O3-1:1 composite in both artificial and natural
water were 95.5 and 87.5% while EC was 1.27 and 1.17 mg/g, respectively. Therefore, the
modified AC-metal oxides electrodes are promising and efficient materials for removing
inorganic pollutants from water, such as Fˉ and organic pollutants, including PQ pesticides for
CDI technolog
Removal of lead ions from water by capacitive deionization electrode materials derived from chicken feathers
No full textThis research article published by IWA Publishing, 2019Capacitive deionization (CDI) is a promising and rapidly growing technology for water treatment and the electrode materials play a key role in improving CDI performance. In this study, high surface area activated carbon was prepared from chicken feather (CF) bio-waste through pyrolysis and KOH activation; the KOH:CF ratio (R) and activation temperature (Ta) were variable parameters. The material was characterized by using the Brunauer, Emmett and Teller (BET) method, Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM). The lead (Pb2+) removal test was performed with a CDI cell containing the fabricated carbon electrode and 100 mg L−1 Pb(NO3)2 solution; the sample prepared with the ratio R of 1:1 and Ta = 800 °C exhibited higher Pb2+ removal efficiency of 81% and electro sorption capacity of 4.1 mg g−1 at the electrode potential 1.2 V and flow rate 5 mL min−1. Therefore, CF-derived carbon is considered as a promising CDI electrode material for removal of heavy metals from waste water
Capacitive deionization: a promising technology for water defluoridation: a review
Full text linkThis research article was published by IWA publishing, Volume 22, No. 1, 2021Capacitive deionization (CDI) is among the promising technologies employed for water purification. CDI has been studied for the removal of
various ionic species from water including fluoride ion (F ) with promising results. However, there is no comprehensive literature that sum marizes the use of CDI for water defluoridation applications. Therefore, this review paper critically analyzes different electrode materials that
have been studied for water defluoridation, their electrosorption capacities and F removal efficiencies. It further discussed the parameters
that influence CDI efficiency during defluoridation and point out the issues of F selectivity when co-existing with other ions in the solution.
We can conclude that different electrode materials have shown different abilities in electrosorption of F . The carbon-based materials pos sess high surface area and good electrical conductivity which is paramount for ion adsorption but gives lack selectivity for F removal. Metal
oxides and hydroxides have been reported with improved electrosorption capacity and high selectivity to F due to the ion exchange
between the F and the hydroxyls surface of the metal oxides/hydroxides. Apart from the good performance of these materials for defluor idation, the discovery of actual practical use of the electrode materials for defluoridation for commercial scal
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
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
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