1,720,961 research outputs found
Gliclazide Removal Efficiency of Carbon‐Based Magnetic Materials: Isotherm and Kinetic Studies
Get PDFGliclazide, one of the micropollutants that can be detected in water, is widely used in the treatment of type II diabetes patients. In this study, the removal of gliclazide from aqueous solutions with magnetic carbon-based materials was investigated. Magnetic activated carbon (MAC) and magnetic multiwalled carbon nanotube (MMWCNT) adsorbents were prepared and characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, and thermogravimetric analysis methods. The effects of various parameters affecting the adsorption process were examined. The adsorption systems were compatible with the Langmuir isotherm model and the pseudo-second-order kinetic model. The maximum monolayer adsorption capacities of the MAC adsorbent (298 K) and the MMWCNT (308 K) were 109.20 and 71.59 mg g(-1), respectively. According to desorption studies, adsorbents could be regenerated by around 70 % in 6 hours
Synthesis, Characterization, and Thermal Pyrolysis Mechanism of Resorcinol-Formaldehyde Resin-Containing Phenylboronic Acid
Get PDFIn the present study, a resin is synthesized from resorcinol and formaldehyde in the presence of phenylboronic acid. Properties of resins such as free formaldehyde content, total solid content, density, gelation time, viscosity are determined. The chemical structure of the resorcinol-formaldehyde resin and the resorcinol-formaldehyde resin containing phenylboronic acid is confirmed by Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The thermal stability and curing behaviors of the polymers are investigated by thermogravimetric analysis (TGA) and differential scanning calorimetry, respectively. Modification of the resorcinol-formaldehyde resin with a boron source, phenylboronic acid results in a certain increase in thermal stability with a higher residual weight. The 6% PBA loaded polymer has the highest thermal efficiency, so the thermal behavior of it is investigated by curing at different temperatures. The 80 degrees C/4 h curing method is the most reasonable for energy savings. In differential scanning calorimetry (DSC) analysis, a 6 wt% PBA loading ratio was determined as the optimum value according to the energy requirements. In this study, a resin is synthesized from resorcinol and formaldehyde in the presence of phenylboronic acid. The 80 degrees C/4 h curing method is the most reasonable for energy savings. While the char residue yield of pure RR resin was 47.9%, the char residue yield of RRB6 resin increased to 54.9%.image (c) 2024 WILEY-VCH GmbHTUEBITAK [221M609]The authors would like to acknowledge the financial support to this work provided by the TUEBITAK through grant no. 221M609
Removal of toxic Cr(VI) from aqueous medium with effective magnetic carbon-based nanocomposites
Get PDFCr(VI), which has toxic effects, is a heavy metal and it must be removed from the environment due to the various damages it causes. In this study, the removal of Cr(VI) pollutants from aqueous solutions with Fe3O4-based materials using a batch adsorption technique was investigated. Magnetically modified graphene nanoplatelet (GNP)-based nanocomposites were prepared and their structures were characterized by FTIR, XRD, SEM, BET, and TGA techniques. The effects of various physicochemical parameters such as adsorbent dose, contact time, initial Cr(VI) solution concentration, pH, and the presence of coexisting ions (NaCl) on the adsorption process were investigated. Accordingly, the optimum conditions for Cr(VI) removal were determined. Nonlinear Langmuir, Freundlich, and Temkin isotherm models and pseudo-first-order, pseudo-second-order, and Bangham kinetic models were used to investigate the adsorption mechanism. The experimental data relatively fit the second-order kinetic model and the Freundlich isotherm model. The maximum adsorption capacities for pure Fe3O4 (Fe:GNP 1:0), Fe:GNP (2:1), and Fe:GNP (1:1) nanocomposite materials at 298 K and pH of approximately 5 were obtained as 12.71 mg/g, 27.03 mg/g, and 62.27 mg/g, respectively. This result showed that Cr(VI) removal increased as the amount of GNP in the composite material increased. Generally, the results confirmed that magnetically modified GNP based adsorbents are functional and promising materials that can be used for the removal of pollutants such as Cr(VI) from aqueous media.Istanbul Beykent University Research Fund [2020-21-BAP-10]This research was supported by the Istanbul Beykent University Research Fund through Project Number 2020-21-BAP-10
Synthesis of PET-based urethane-modified alkyd resins from depolymerization intermediates of post-consumer PET bottles: coating properties and thermal behaviors
No full text© 2022, American Coatings Association.Abstract: Urethane-modified alkyd resins were synthesized using the depolymerization intermediates obtained from simultaneous hydrolysis–glycolysis reactions of post-consumer poly(ethylene terephthalate) (PET) bottles with dipropylene glycol (DPG) and water. For this aim, first, the synthesis of a four-component reference alkyd resin having an oil content of 50% was synthesized by using tall oil fatty acid (TOFA), trimethylolpropane (TMP), phthalic anhydride (PA), and dipropylene glycol (DPG). The PET-based alkyd resins were also synthesized using different amounts and types of purified and fractionated depolymerization intermediates (water-insoluble fraction, WIF, and water-soluble and crystallizable fraction, WSCF) under the same reaction conditions. For the synthesis of PET-based alkyd resins, the depolymerization intermediates were used partially or completely instead of dibasic acid and/or diol components in alkyd resin formulations. In order to determine the optimum modification ratio for urethane-modified alkyd resin synthesis, the reference alkyd resin was reacted with toluene diisocyanate (TDI) at different molar ratios (NCO/OH: 1/1, 1/2, and 1/3), and the optimum NCO/OH ratio was determined as 1/1, according to the surface coating properties. And, then, all PET-based urethane-modified alkyd resins were prepared by the modification reactions of the PET-based alkyd resins with TDI at an optimum ratio. At the end of the study, it was observed that the use of waste PET intermediates (WIF or WSCF) did not cause any negative effects on physical/chemical surface coating and thermal properties; on the contrary, some properties were obtained as superior than that of the reference resin. In conclusion, it seems possible to use PET-based urethane-modified alkyd resin could be used as a cheap, environmentally friendly, and relatively economic binder component in synthetic paint formulations. In the synthesis of urethane-modified alkyd resin, using a certain amount of waste PET intermediate instead of dibasic acid and/or diol component will reduce raw material costs and also benefit the environment by re-evaluation of recycled PET. Thus, it could be both possible to recycle of post-consumer PET bottles, which are a valuable waste, and to provide cheap raw materials without compromising its features for paint formulations. These results are remarkable in terms of sustainability and waste management besides are also important for the economy and paint industry. Graphical Abstract: [Figure not available: see fulltext.]
Comparative Investigation of Phosphate Adsorption Efficiencies of MOF-76 (Ce) and Metal Oxides Derived from MOF-76 (Ce)
Get PDFPhosphate pollution is a very challenging problem for the water environment. Phosphate mixed with water in various ways causes eutrophication. To sustain life in aquatic systems, phosphate ions must be cleaned. Therefore, it is very important to remove phosphate in wastewater. Here, an adsorption method has been tried for the removal of phosphate. MOF-76 (Ce), a cerium-based metal-organic framework, was synthesized by a hydrothermal method. Since metal oxides are known to be successful in phosphate adsorption, CeO2 nanoparticles were also obtained by pyrolysis of this MOF structure. The phosphate adsorption efficiencies of both adsorbents were compared. The characterization methods (SEM, FTIR, XRD, and TGA) were applied to adsorbents. The kinetic, isotherm, and thermodynamics studies were applied to experimental results. At 298 K, the adsorption capacity of MOF-76 (Ce) is higher than that of CeO2, according to Langmuir isotherm q(m) values. The q(m) values are 72.97 and 55.71 mg/g, respectively. Both adsorbents follow the pseudo second-order kinetic model. It has been found that MOF-76 (Ce) has a pH-selective property in phosphate adsorption. No change was observed in the phosphate adsorption capacity of CeO2 with pH. In terms of thermodynamics, the endothermic reaction is valid for both adsorbents
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
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