Artículos de revistas: "Oxydes de carbon"

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El-Nabarawy, Th, N. Sh Petro y S. Abdel-Aziz. "Adsorption Characteristics of Coal-based Activated Carbons. II. Adsorption of Water Vapour, Pyridine and Benzene". Adsorption Science & Technology 15, n.º 1 (febrero de 1997): 47–57. http://dx.doi.org/10.1177/026361749701500105.

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Chemically-activated carbons were prepared by carbonizing Maghara coal with different amounts of phosphoric acid at 873 K. Steam-activated carbons of different burn-off were prepared by gasifying non-activated carbon prepared by carbonization at 873 K with steam at 1173 K. Samples of steam-activated carbons were also treated with concentrated nitric acid or with potassium dichromate. The adsorption of water vapour and benzene was determined at 308 K. The adsorption of pyridine was followed on the chemically-activated carbons at 343 K. The adsorption of water vapour was found to be related to the surface area and the amount of carbon–oxygen groups. Some of the adsorbed water was found to be specifically held to the surface and could be used to determine the number of carbon–oxygen groups on the surface. Two mechanisms are involved in the adsorption of pyridine on the carbons investigated. These are physisorption on the oxygen-free surface and chemisorption on carbon–oxygen groups of an acidic nature. Benzene may be vertically oriented in micropores, horizontally oriented in wider pores and may be even inaccessible to the fraction of the surface located in ultramicropores. Benzene adsorption is also retarded by the existence of a high concentration of carbon–oxygen groups oh the surface.

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2

Yuen, Pong Kau y Cheng Man Diana Lau. "Using Mean Oxidation Number of Organic Carbons to Count Theoretical Chemical Oxygen Demand". International Journal of Chemistry 16, n.º 1 (21 de marzo de 2024): 88. http://dx.doi.org/10.5539/ijc.v16n1p88.

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Chemical oxygen demand and mean oxidation number of organic carbons are two important concepts in redox chemistry. The former is used for counting pure or mixed organic matters in aqueous solution. The latter is a redox metric for water treatment, organic combustion, and anaerobic digestion. Currently the calculation of theoretical chemical oxygen demand of neutral organic matter is based on the number of moles of molecular oxygen (O2). However, the calculation of theoretical chemical oxygen demand of ionic organic matter has seldom been studied. The purpose of this article is to develop a simple mathematical equation for doing so by using mean oxidation number of organic carbons. To develop the equation, relationships among chemical oxygen demand, mean oxidation number of organic carbons, number of organic carbons, and formula mass of organic matter are identified. The mathematical equations for chemical oxygen demand, total organic carbon, and the ratio of chemical oxygen demand to total organic carbon are also established for any molecule(s).

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3

El-Nabarawy, Th, G. A. Fagal y L. B. Khalil. "Removal of Ammonia from Aqueous Solution Using Activated Carbons". Adsorption Science & Technology 13, n.º 1 (febrero de 1996): 7–13. http://dx.doi.org/10.1177/026361749601300102.

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The surface areas of non-activated, activated and modified activated carbons were determined from the adsorption of nitrogen at −196°C and of carbon dioxide at 25°C. The base neutralization capacities were determined from the adsorption of NaOH, Na2CO3, NaHCO3 and NH4OH. The amount of oxygen combined to the carbon surface was estimated by measuring the pressure of CO and CO2 obtained on outgassing the carbon sample in the temperature range 300–1000°C. The surface area of activated carbon is not a determining factor in its ammonia adsorption. The surface acidity of the active carbon is a good measure of its capacity for ammonia removal. Ammonia adsorption increases appreciably upon surface oxidation of carbons with oxidizing gases and solutions. The acidic groups on the surface of carbons differ in their strength. Only a fraction of the surface covered by the carbon–oxygen groups is responsible for the capacity of the carbon towards ammonia. Most of the adsorbed ammonia is recovered upon treatment with dilute hydrochloric acid leaving the surface free for successive ammonia adsorption cycles.

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4

Renlund, Gary M., Svante Prochazka y Robert H. Doremus. "Silicon oxycarbide glasses: Part II. Structure and properties". Journal of Materials Research 6, n.º 12 (diciembre de 1991): 2723–34. http://dx.doi.org/10.1557/jmr.1991.2723.

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Silicon oxycarbide glass is formed by the pyrolysis of silicone resins and contains only silicon, oxygen, and carbon. The glass remains amorphous in x-ray diffraction to 1400 °C and shows no features in transmission electron micrographs (TEM) after heating to this temperature. After heating at higher temperature (1500–1650 °C) silicon carbide lines develop in x-ray diffraction, and fine crystalline regions of silicon carbide and graphite are found in TEM and electron diffraction. XPS shows that silicon-oxygen bonds in the glass are similar to those in amorphous and crystalline silicates; some silicons are bonded to both oxygen and carbon. Carbon is bonded to either silicon or carbon; there are no carbon-oxygen bonds in the glass. Infrared spectra are consistent with these conclusions and show silicon-oxygen and silicon-carbon vibrations, but none from carbon-oxygen bonds. 29Si-NMR shows evidence for four different bonding groups around silicon. The silicon oxycarbide structure deduced from these results is a random network of silicon-oxygen tetrahedra, with some silicons bonded to one or two carbons substituted for oxygen; these carbons are in turn tetrahedrally bonded to other silicon atoms. There are very small regions of carbon-carbon bonds only, which are not bonded in the network. This “free” carbon colors the glass black. When the glass is heated above 1400 °C this network composite rearranges in tiny regions to graphite and silicon carbide crystals. The density, coefficient of thermal expansion, hardness, elastic modulus, index of refraction, and viscosity of the silicon oxycarbide glasses are all somewhat higher than these properties in vitreous silica, probably because the silicon-carbide bonds in the network of the oxycarbide lead to a tighter, more closely packed structure. The oxycarbide glass is highly stable to temperatures up to 1600 °C and higher, because oxygen and water diffuse slowly in it.

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5

Jiarun, Yin. "Stable carbon and oxygen isotopes in Jurassic shells as palaeosalinity indicators". Neues Jahrbuch für Geologie und Paläontologie - Monatshefte 1991, n.º 3 (4 de marzo de 1991): 163–76. http://dx.doi.org/10.1127/njgpm/1991/1991/163.

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6

LIU, Pou, Fumihito ARAI y Toshio FUKUDA. "1P1-C16 Oxygen Gas Assisted Nanofabrication and Nanoassembly of Carbon Nanotubes". Proceedings of JSME annual Conference on Robotics and Mechatronics (Robomec) 2006 (2006): _1P1—C16_1—_1P1—C16_4. http://dx.doi.org/10.1299/jsmermd.2006._1p1-c16_1.

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7

Holail, Hanafy. "Carbon and oxygen ratios of Middle Eocene dolomite, Gebel Ataqa, Egypt". Neues Jahrbuch für Geologie und Paläontologie - Abhandlungen 191, n.º 1 (13 de abril de 1994): 111–24. http://dx.doi.org/10.1127/njgpa/191/1994/111.

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8

Volperts, Aleksandrs, Ance Plavniece, Kätlin Kaare, Galina Dobele, Aivars Zhurinsh y Ivar Kruusenberg. "Influence of Chemical Activation Temperatures on Nitrogen-Doped Carbon Material Structure, Pore Size Distribution and Oxygen Reduction Reaction Activity". Catalysts 11, n.º 12 (30 de noviembre de 2021): 1460. http://dx.doi.org/10.3390/catal11121460.

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The goal of this research was to synthesize activated nitrogen-doped nanocarbons with high specific surface area and adjustable pore size distribution using wood charcoal as a raw material. The resulting carbon materials were tested for possible application as oxygen reduction reaction catalysts in alkaline media. Activated carbons were obtained using a thermochemical activation method with NaOH. Nitrogen was introduced into activated carbons using dicyandiamide solution. It was demonstrated that the content of introduced nitrogen depends on oxygen content in the structure of the activated carbon. The oxygen reduction reaction activity of the activated and nitrogen-doped carbon material was comparable with a commercial 20% Pt/C catalyst. Electrocatalytic properties of the synthesized N-doped wood-derived carbon catalysts may be associated with the highly developed surface area, specific ratio of micro- and mesopores, as well as the high percentage of pyridinic nitrogen.

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9

Rivera–Utrilla, J. y M. A. Ferro–García. "Effect of Carbon–Oxygen and Carbon–Nitrogen Surface Complexes on the Adsorption of Cations by Activated Carbons". Adsorption Science & Technology 3, n.º 4 (diciembre de 1986): 293–302. http://dx.doi.org/10.1177/026361748600300409.

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Adsorption studies of Na+, Cs+, Ag+, Sr2+ and Co2+ from aqueous solutions by surface-treated activated carbons are reported. Carbon–oxygen and carbon–nitrogen surface complexes were formed on an activated carbon from almond shells by treating it with either oxidizing reagents or ammonia. In order to discover the surface acidity and/or basicity of each carbon, selective neutralization techniques were carried out. Both Na+ and Cs+ are adsorbed by only those carbons containing strong acidic functional groups; however, Ag+, Sr2+ and Co2+ are adsorbed not only by these latter carbons but also by those with predominance of basic groups. The results suggest that some of these carbons can be used to remove, separate and pre-concentrate all the cations studied.

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10

Harris, P. J. F. "Non-Graphitizing Carbon: Its Structure and Formation from Organic Precursors". Eurasian Chemico-Technological Journal 21, n.º 3 (30 de septiembre de 2019): 227. http://dx.doi.org/10.18321/ectj863.

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Non-graphitizing carbon, or char, has been intensively studied for decades, but there is still no agreement about its detailed atomic structure. The first models for graphitizing and non-graphitizing carbons were proposed by Rosalind Franklin in the early 1950s, and while these are correct in a broad sense, they are incomplete. Subsequent models also fail to explain fully the structure of non-graphitizing carbons. The discovery of the fullerenes and related structures stimulated the present author and others to put forward models which incorporate non-hexagonal rings into hexagonally-bonded sp2 carbon networks, creating a microporous structure made up of highly curved fragments. However, this model has not been universally accepted. This paper reviews the models that have been put forward for non-graphitizing carbon and outlines the evidence for a fullerene-like structure. This evidence comes from transmission electron microscopy, electron energy loss spectroscopy and Raman spectroscopy. Finally, the influence of precursor chemistry on the structure of graphitizing and non-graphitizing carbons is discussed. It is well established that carbonization of oxygen–containing precursors tends to produce non-graphitizing carbons. This may be explained by the fact that the removal of oxygen from a hexagonal carbon network can result in the formation of pentagonal carbon rings.

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11

Minh, Doan Pham, Thanh Son Phan, Didier Grouse y Ange Nzihou. "Thermodynamic Equilibrium Study of Methane Reforming with Carbon Dioxide, Water and Oxygen". Journal of Clean Energy Technologies 6, n.º 4 (julio de 2018): 309–13. http://dx.doi.org/10.18178/jocet.2018.6.4.480.

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12

Goliáš, J., A. Němcová, A. Čaněk y D. Kolenčíková. "Storage of sweet cherries in low oxygen and high carbon dioxide atmospheres". Horticultural Science 34, No. 1 (7 de enero de 2008): 26–34. http://dx.doi.org/10.17221/1843-hortsci.

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Acetaldehyde and ethanol are already present in detectable levels at the time of harvest, under aerobic conditions and in healthy, undamaged fruit. Both metabolites can be detected, at different concentrations, in all cultivars. Several hours after harvest, the levels of acetaldehyde in cultivars Summit, Techlovan and Kordia were 6.41, 9.78 and 22.00 mg/l, respectively. Both ethanol and acetaldehyde accumulate to significant levels in anaerobically stored cherries, particularly in atmospheres with high levels of CO2. The highest levels of ethanol observed, after 31 days of exposure to anaerobic conditions, were in the cultivars Techlovan (1,159 mg/l) and Summit (1,168 mg/l); both concentrations are are broadly similar. The metabolites decreased after a return to aerobic conditions, but remained higher than the levels first observed. Sweet cherries stored in anaerobic conditions are also sensitive to the development of off-flavours in the first 24 hours after opening the storage box. The very slow ripening of the fruit under anaerobic conditions was satisfactorily quantified by measuring the higher degree of fruit firmness, when the usual, visual attributes of ripeness were almost undetectable. Stems also remained green, in contrast to the usual browning that occurs under normal atmospheres. Discrimination analysis of various parameters observed gave a good resolution of different cultivars.

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13

Nkiawete, Mpila Makiesse y Randy Vander Wal. "Thermo-Catalytic Decomposition Comparisons: Carbon Catalyst Structure, Hydrocarbon Feed and Regeneration". Catalysts 13, n.º 10 (20 de octubre de 2023): 1382. http://dx.doi.org/10.3390/catal13101382.

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Thermo-catalytic decomposition (TCD) activity and stability depend upon the initial carbon catalyst structure. However, further transitions in the carbon structure depend on the carbon material (structure and composition) originating from the TCD process. In this article, reaction data are presented that illustrates the time-dependent TCD activity as TCD-formed carbon contributes and then dominates conversion. A variety of initial carbon catalysts are compared, including sugar char, a conductive carbon black (AkzoNobel Ketjenblack), a rubber-grade carbon black (Cabot R250), and its graphitized analogue as formed and partially oxidized. Regeneration of carbon catalysts by partial oxidation is evaluated using nascent carbon black as a model, coupled with subsequent comparative TCD performance relative to the nascent, non-oxidized carbon black. Activation energies for TCD with nascent and oxidized carbons are evaluated by a leading-edge analysis method applied to TCD. Given the correlation between nanostructure and active sites, two additional carbons, engine soots, are evaluated for regeneration and dependence upon nanostructure. Active sites are quantified by oxygen chemisorption, followed by X-ray photoelectron spectroscopy (XPS). The structure of carbon catalysts is assessed pre- and post-TCD by high-resolution transmission electron microscopy (HRTEM). Last, energy dispersive X-ray analysis mapping (EDS) is carried out for its potential to visualize oxygen chemisorption.

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14

Yang, Wen, Yanjie Li y Yanyan Feng. "High Electrochemical Performance from Oxygen Functional Groups Containing Porous Activated Carbon Electrode of Supercapacitors". Materials 11, n.º 12 (4 de diciembre de 2018): 2455. http://dx.doi.org/10.3390/ma11122455.

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Carbon electrode materials for double layer capacitors have attracted much attention, due to their low cost and abundant sources. Their low specific capacitance, however, hinders the development of carbon electrode materials. In this paper, the large specific surface area commercial activated carbons, rich in micropores, were initially oxygen-functionalized by treatment using concentrated H2SO4, saturated (NH4)2S2O8, and H2SO4/(NH4)2S2O4 mixed oxidants, respectively. The as-prepared samples were analyzed using N2 adsorption/desorption isotherms, X-ray photoelectron spectroscopy, and Boehm titration, and used as electrode materials for supercapacitors. Characterization results displayed that the oxidation treatment decreased the specific surface area along with increasing oxygen content. The electrode test showed that the electrochemical activity increased as oxygen content increased. The result that oxygen-functionalized activated carbon, even with a lower specific surface area but much more oxygen content, had higher capacity than pristine activated carbon, tells of the critical role of oxygen functional groups. The excellent capacitive performance suggests a good potential for oxygen functional carbon material to be a highly promising electrode material for supercapacitors.

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15

Gadipelli, Srinivas, Zhuangnan Li, Tingting Zhao, Yuchen Yang, Taner Yildirim y Zhengxiao Guo. "Graphitic nanostructures in a porous carbon framework significantly enhance electrocatalytic oxygen evolution". Journal of Materials Chemistry A 5, n.º 47 (2017): 24686–94. http://dx.doi.org/10.1039/c7ta03027d.

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Hybrid carbons, nickel embedded nanographites in a nitrogen-doped porous carbon structure, developed by a simplified CVD fashion, utilizing a solid state precursor, zeolitic-imidazolate-framework, lead to highly enhanced water oxidation activity over simple graphitic or porous carbon based structures alone.

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16

Wang, Guanxiong, Wei Zhao, Majid Mansoor, Yinan Liu, Xiuyue Wang, Kunye Zhang, Cailin Xiao et al. "Recent Progress in Using Mesoporous Carbon Materials as Catalyst Support for Proton Exchange Membrane Fuel Cells". Nanomaterials 13, n.º 21 (24 de octubre de 2023): 2818. http://dx.doi.org/10.3390/nano13212818.

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Developing durable oxygen reduction reaction (ORR) electrocatalysts is essential to step up the large-scale applications of proton exchange membrane fuel cells (PEMFCs). Traditional ORR electrocatalysts provide satisfactory activity, yet their poor durability limits the long-term applications of PEMFCs. Porous carbon used as catalyst support in Pt/C is vulnerable to oxidation under high potential conditions, leading to Pt nanoparticle dissolution and carbon corrosion. Thus, integrating Pt nanoparticles into highly graphitic mesoporous carbons could provide long-term stability. This Perspective seeks to reframe the existing approaches to employing Pt alloys and mesoporous carbon-integrated ORR electrocatalysts to improve the activity and stability of PEMFCs. The unusual porous structure of mesoporous carbons promotes oxygen transport, and graphitization provides balanced stability. Furthermore, the synergistic effect between Pt alloys and heteroatom doping in mesoporous carbons not only provides a great anchoring surface for catalyst nanoparticles but also improves the intrinsic activity. Furthermore, the addition of Pt alloys into mesoporous carbon optimizes the available surface area and creates an effective electron transfer channel, reducing the mass transport resistance. The long-term goals for fuel-cell-powered cars, especially those designed for heavy-duty use, are well aligned with the results shown when this hybrid material is used in PEMFCs to improve performance and durability.

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17

Sun, Jing, Shujin Wang, Yinghua Wang, Haibo Li, Huawei Zhou, Baoli Chen, Xianxi Zhang, Hongyan Chen, Konggang Qu y Jinsheng Zhao. "One Simple Strategy towards Nitrogen and Oxygen Codoped Carbon Nanotube for Efficient Electrocatalytic Oxygen Reduction and Evolution". Catalysts 9, n.º 2 (6 de febrero de 2019): 159. http://dx.doi.org/10.3390/catal9020159.

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The development of advanced electrocatalysts for oxygen reduction and evolution is of paramount significance to fuel cells, water splitting, and metal-air batteries. Heteroatom-doped carbon materials have exhibited great promise because of their excellent electrical conductivity, abundance, and superior durability. Rationally optimizing active sites of doped carbons can remarkably enhance their electrocatalytic performance. In this study, nitrogen and oxygen codoped carbon nanotubes were readily synthesized from the pyrolysis of polydopamine-carbon nanotube hybrids. Different electron microscopes, Raman spectra and X-ray photoelectron spectroscopy (XPS) were employed to survey the morphological and componential properties. The newly-obtained catalyst features high-quality nitrogen and oxygen species, favourable porous structures and excellent electric conductivity, and thus exhibits remarkably bifunctional oxygen electrode activity. This research further helps to advance the knowledge of polydopamine and its potential applications as efficient electrocatalysts to replace noble metals.

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18

Park, Soo Jin y Jun-Sik Shin. "Anodization of Nanoporous Carbons for Removal of Ammonia". Journal of Metastable and Nanocrystalline Materials 23 (enero de 2005): 7–10. http://dx.doi.org/10.4028/www.scientific.net/jmnm.23.7.

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In this study, a new nanoporous carbon was prepared by anodic oxidation treatment to remove noxic ammonia gas. The acid- and base values of the nanoporous carbon were determined by Boehm’s titration method. And, the surface properties of the carbons were investigated by XPS analysis. Also, N2/77K adsorption isotherm characteristics, including the specific surface areas and nano/micropore volumes were studied by BET and t-plot methods, respectively. The ammonia removal efficiency was confirmed by gas-detecting tube technique. As a result, it was revealed in the case of acidic treatment on nanoporous carbons that the ammonia removal was greatly effective due to the increase of OH groups in carbon surfaces without significant changes of nanostructural properties. It was then found that the acidic anodization of nanoporous carbons was a suitable method for the effective removal of ammonia gas, which could be attributed to the increase of acceptor-donor interactions between acidic oxygen functional groups of carbon adsorbent and basic adsorbate in an adsorbent-adsorbate system.

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19

Morais, Rafael G., Natalia Rey-Raap, Rui S. Costa, Clara Pereira, Alexandra Guedes, José L. Figueiredo y M. Fernando R. Pereira. "Hydrothermal Carbon/Carbon Nanotube Composites as Electrocatalysts for the Oxygen Reduction Reaction". Journal of Composites Science 4, n.º 1 (17 de febrero de 2020): 20. http://dx.doi.org/10.3390/jcs4010020.

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The oxygen reduction reaction is an essential reaction in several energy conversion devices such as fuel cells and batteries. So far, the best performance is obtained by using platinum-based electrocatalysts, which make the devices really expensive, and thus, new and more affordable materials should be designed. Biomass-derived carbons were prepared by hydrothermal carbonization in the presence of carbon nanotubes with different oxygen surface functionalities to evaluate their effect on the final properties. Additionally, nitrogen functional groups were also introduced by ball milling the carbon composite together with melamine. The oxygen groups on the surface of the carbon nanotubes favor their dispersion into the precursor mixture and the formation of a more homogenous carbon structure with higher mechanical strength. This type of structure partially avoids the crushing of the nanotubes and the carbon spheres during the ball milling, resulting in a carbon composite with enhanced electrical conductivity. Undoped and N-doped composites were used as electrocatalysts for the oxygen reduction reaction. The onset potential increases by 20% due to the incorporation of carbon nanotubes (CNTs) and nitrogen, which increases the number of active sites and improves the chemical reactivity, while the limiting current density increases by 47% due to the higher electrical conductivity.

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20

Momcilovic, Milan, Milovan Purenovic, Milena Miljkovic, Aleksandar Bojic, Aleksandra Zarubica y Marjan Randjelovic. "Physico-chemical characterization of powdered activated carbons obtained by thermo-chemical conversion of brown municipal waste". Chemical Industry 65, n.º 3 (2011): 241–47. http://dx.doi.org/10.2298/hemind110124016m.

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Cones of the European Black pine and Horse chestnut kernel, regarded as brown municipal waste, was utilized in this work as a precursor for powdered activated carbons. Chemical activation was employed at 500?C in inert atmosphere of nitrogen. Standard physico-chemical analyses were performed to examine obtained products. FTIR method was employed to determine fuctional groups which were found to be typical for activated carbons. Acidic oxygen groups were quantitatively determined using Boehm titrations. It was established that carboxylic groups on pine cone activated carbon, and phenolic groups on chestnut kernel activated carbon were dominant from all acidic oxygen groups. Since both contact pH and pHPZC were determined to be fairly acidic, it could be concluded that obtained activated carbons belong to L-type. Shape and layout of micrometer dimensioned particles were observed by scanning electron microscopy. Particles of different shapes and dimensions along with small cracks and wide crevices and voids were noticed. Textural analysis was used to determine specific surface area and pore distribution of obtained activated carbons. Obtained products possess highly developed surface area and wide pore distribution.

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Ponce, M. A., C. M. Aldao y M. S. Castro. "Efectos de la exposición de películas gruesas de SnO₂ a vacío, oxígeno y monóxido de carbono". Boletín de la Sociedad Española de Cerámica y Vidrio 41, n.º 1 (28 de febrero de 2002): 147–50. http://dx.doi.org/10.3989/cyv.2002.v41.i1.714.

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22

Liu, Fei, Yaqi Ren y Xixi Ji. "Nanosheet-Structured Boron Carbon Nitride Spheres as Stable Electrocatalyst Support for Oxygen Reduction Reaction". International Journal of Materials Science and Engineering 5, n.º 4 (2017): 123–32. http://dx.doi.org/10.17706/ijmse.2017.5.4.123-132.

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23

Kostrobij, P., A. Beznosiuk, V. Dmytruk y V. Polovyi. "Modeling of Pt-catalyst surface influence on characteristics of oxygen and carbon monoxide molecules". Mathematical Modeling and Computing 3, n.º 1 (1 de julio de 2016): 43–50. http://dx.doi.org/10.23939/mmc2016.01.043.

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Frilund, Christian, Ilkka Hiltunen y Pekka Simell. "Activated Carbons for Syngas Desulfurization: Evaluating Approaches for Enhancing Low-Temperature H2S Oxidation Rate". ChemEngineering 5, n.º 2 (11 de mayo de 2021): 23. http://dx.doi.org/10.3390/chemengineering5020023.

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Its relatively low cost and high surface area makes activated carbon an ideal adsorbent candidate for H2S removal. However, physical adsorption of H2S is not very effective; therefore, methods to facilitate reactive H2S oxidation on carbons are of interest. The performance of H2S removal of non-impregnated, impregnated, and doped activated carbon in low-temperature syngas was evaluated in fixed-bed breakthrough tests. The importance of oxygen content and relative humidity was established for reactive H2S removal. Impregnates especially improved the adsorption rate compared to non-impregnated carbons. Non-impregnated carbons could however retain a high capture capacity with sufficient contact time. In a relative performance test, the best performance was achieved by doped activated carbon, 320 mg g−1. Ammonia in syngas was found to significantly improve the adsorption rate of non-impregnated activated carbon. A small quantity of ammonia was consumed by the carbon bed, suggesting that ammonia is a reactant. Finally, to validate ammonia-enhanced desulfurization, bench-scale experiments were performed in biomass-based gasification syngas. The results show that when the ammonia concentration in syngas was in the tens of ppm range, 40–160 ppm H2S oxidation proceeded rapidly. Ammonia-enhanced oxidation allows utilization of cheaper non-impregnated activated carbons by in situ improvement of the adsorption kinetics. Ammonia enhancement is therefore established as a viable method for achieving high-capacity H2S removal with unmodified activated carbons.

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Gomis-Berenguer, Alicia, Irma Eliani, Vânia F. Lourenço, Rocio J. Carmona, Leticia F. Velasco y Conchi O. Ania. "Insights on the Use of Carbon Additives as Promoters of the Visible-Light Photocatalytic Activity of Bi2WO6". Materials 12, n.º 3 (26 de enero de 2019): 385. http://dx.doi.org/10.3390/ma12030385.

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We have explored the impact of the incorporation of various amounts of carbons from varied physicochemical features as additives to Bi2WO6 for the photocatalytic degradation of a dye using simulated solar light. Data has revealed that the composition and acidic character of the carbon additive are important parameters in the performance of the Bi2WO6/carbon catalysts. The presence of a carbon additive improved the conversion of the dye, evidencing the occurrence of charge transfer reactions that involve radical mediated reactions. The catalysts prepared with 2 and 5 wt.% of carbon additive outperformed the bare semiconductor, despite the shielding effect of the carbon matrix. The acidic nature of the Bi2WO6/carbon catalysts governs the degradation pathway (due to the preferential adsorption of the dye), that proceeds via the deethylation of the auxochrome groups of the dye at short irradiation times, followed by the cleavage of the chromophore at long irradiation times. Regarding the characteristics of the carbons, the photocatalytic degradation rate is accelerated by carbons of acidic character and high oxygen content, whereas the porosity seems to play a minor role. The presence of the carbon additives also affects the toxicity of the treated solutions, rendering lower values after shorter irradiation periods.

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Kamedulski, Piotr, Malgorzata Skorupska, Izabela Koter, Maciej Lewandowski, Víctor Karim Abdelkader-Fernández y Jerzy P. Lukaszewicz. "Obtaining N-Enriched Mesoporous Carbon-Based by Means of Gamma Radiation". Nanomaterials 12, n.º 18 (12 de septiembre de 2022): 3156. http://dx.doi.org/10.3390/nano12183156.

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In this paper, we present the results of the gamma irradiation method to obtain N-doped mesoporous activated carbons. Nitrogen-enriched mesoporous carbons were prepared from three chosen commercial activated carbons such as Carbon Black OMCARB C-140, KETJENBLACK EC-600JD and PK 1-3 Norit. HRTEM, SEM, Raman spectra, elemental analysis, XPS studies and widely approved N2 adsorption–desorption measurements allowed us to evaluate the effectiveness of N atom insertion and its influence on the BET surface area and the pore structure of modified carbons. The obtained materials have an exceptionally high N content of up to 3.2 wt.%. Additionally, selected N-doped activated carbons were fully characterized to evaluate their applicability as carbon electrode materials with particular emphasis on Oxygen Reduction Reaction (ORR). The proposed method is a relatively facile, efficient and universal option that can be added to the already known methods of introducing heteroatoms to different carbons.

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Zhang, Rui, Haibo Li, Rui Li, Denghu Wei, Wenjun Kang, Zhicheng Ju y Shenglin Xiong. "Boosting the potassium-ion storage performance of a carbon anode by chemically regulating oxygen-containing species". Chemical Communications 55, n.º 94 (2019): 14147–50. http://dx.doi.org/10.1039/c9cc07585b.

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The oxygen-containing species in melamine foam carbons are chemically regulated. The optimized carbon anode shows an enhanced potassium-ion storage performance in terms of reversible capacity, rate capability, and long-term cycling stability.

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Goscianska, Joanna, Aleksander Ejsmont, Anna Olejnik, Dominika Ludowicz, Anna Stasiłowicz y Judyta Cielecka-Piontek. "Design of Paracetamol Delivery Systems Based on Functionalized Ordered Mesoporous Carbons". Materials 13, n.º 18 (18 de septiembre de 2020): 4151. http://dx.doi.org/10.3390/ma13184151.

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The oxidized ordered mesoporous carbons of cubic and hexagonal structure obtained by two templating methods (soft and hard) were applied for the first time as delivery systems for paracetamol—the most common antipyretic and analgesic drug in the world. The process of carbon oxidation was performed using an acidic ammonium persulfate solution at 60 °C for 6 h. The functionalization was found to reduce the specific surface area and pore volume of carbon materials, but it also led to an increasing number of acidic oxygen-containing functional groups. The most important element and the novelty of the presented study was the evaluation of adsorption and release ability of carbon carriers towards paracetamol. It was revealed that the sorption capacity and the drug release rate were mainly affected by the materials’ textural parameters and the total amount of surface functional groups, notably different in pristine and oxidized samples. The adsorption of paracetamol on the surface of ordered mesoporous carbons occurred according to different mechanisms: donor–acceptor complexes and hydrogen bond formation. The adsorption kinetics was assessed using pseudo-first- and pseudo-second-order models. The regression results indicated that the adsorption kinetics was more accurately represented by the pseudo-second-order model. Paracetamol was adsorbed onto the carbon materials studied following the Langmuir type isotherm. The presence of oxygen-containing functional groups on the surface of ordered mesoporous carbons enhanced the amount of paracetamol adsorbed and its release rate. The optimal drug loading capacity and expected release pattern exhibited oxidized ordered mesoporous carbon with a hexagonal structure obtained by the hard template method.

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Choma, J. y M. Jaroniec. "Estimation of the Surface Properties of Unmodifed and Strongly Oxidized Active Carbons on the Basis of Water Vapour Adsorption Isotherms". Adsorption Science & Technology 16, n.º 4 (abril de 1998): 295–302. http://dx.doi.org/10.1177/026361749801600406.

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Water vapour adsorption isotherms were measured for a series of commercial active carbons and one carbon black oxidized with concentrated nitric acid at its boiling temperature. A comparative analysis of the surface properties of the unmodified and strongly oxidized active carbons was performed on the basis of the adsorption potential distributions (APDs) calculated from these adsorption isotherms. It was shown that the APDs for oxidized carbons exhibit some extra details (e.g., peaks) in the range of high adsorption potentials which can be assigned to interactions of water molecules with oxygen surface groups formed during the oxidation process. This is especially visible for oxidized carbon black. The observed sensitivity of the APDs obtained from water vapour adsorption isotherms make them attractive functions for monitoring the surface changes in active carbons due to their oxidation.

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30

Kim, Yong Tae, Eun Duck Park, Min Kang y Jae Eui Yie. "The Effect of Physicochemical Treatment on Pd Dispersion of Carbon-Supported Pd Catalysts". Solid State Phenomena 135 (febrero de 2008): 57–60. http://dx.doi.org/10.4028/www.scientific.net/ssp.135.57.

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Carbon-supported palladium catalysts were prepared by an impregnation method using palladium chloride and different carbon supports such as activated carbons with different surface oxygen concentrations and a mesoporous carbon, CMK-5.. The different degree of surface oxidation was achieved by the nitric acid and high-temperature heat treatment. The molecular PdCl2 species was stabilized by adding an HCl in an impregnation step.. As the reduction temperature increased, the Pd dispersion decreased for all Pd catalysts. There was no noticeable difference in Pd dispersion among Pd catalysts supported on carbon supports with different physicochemical properties when the reduction temperature was 423 K. Pd catalysts supported on the carbon support with a high concentration of surface oxygen groups showed a better dispersion than did other Pd catalysts when they were reduced at 573 K. The maximum Pd dispersion was observed over Pd catalyst supported on carbon supports with the highest surface area when the reduction temperature was higher than 573 K.

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31

Belhachemi, Meriem y Fatima Addoun. "Effect of Heat Treatment on the Surface Properties of Activated Carbons". E-Journal of Chemistry 8, n.º 3 (2011): 992–99. http://dx.doi.org/10.1155/2011/649254.

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This work reports the effect of heat treatment on the porosity and surface chemistry of two series of activated carbons prepared from a local agricultural biomass material, date pits, by physical activation with carbon dioxide and steam. Both series samples were oxidized with nitric acid and subsequently heat treated under N2at 973 K in order to study the effect of these treatments in porosity and surface functional groups of activated carbons. When the activated carbons were heat treated after oxidation the surface area and the pore volume increase for both activated carbons prepared by CO2and steam activations. However the amount of surface oxygen complexes decreases, the samples keep the most stable oxygen surface groups evolved as CO by temperature-programmed desorption experiments at high temperature. The results show that date pits can be used as precursors to produce activated carbons with a well developed porosity and tailored oxygen surface groups.

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32

Panov, Yevgen, Nikolai Gomelia, Olena Ivanenko, Andrii Vahin y Serhii Leleka. "Determination of the Conditions for Carbon Materials Oxidation with Carbon Monoxide Formation at High Temperatures". Chemistry & Chemical Technology 14, n.º 4 (15 de diciembre de 2020): 545–52. http://dx.doi.org/10.23939/chcht14.04.545.

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In this paper, the influence of carbon material type, temperature and oxygen concentration in gas mixture on the processes of carbon monoxide formation in production of the electrodes by graphitization was explored experimentally. Specific quantity of gas formed for a definite time, reduced to mass unit of carbon loading using pitch, packing materials and charge mixture of industrial use, was calculated. It is demonstrated that pitch provides the highest rate of carbon oxidation with the release of CO and substantially exceeds packing materials and charge mixture for this index.

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33

Zhou, Jin y Shu Ping Zhuo. "Capacitive Performance of Ordered Mesoporous Carbons in Ionic Liquids". Advanced Materials Research 284-286 (julio de 2011): 2086–89. http://dx.doi.org/10.4028/www.scientific.net/amr.284-286.2086.

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Ordered mesoporous carbons (BOMC) were prepared by doping boric acid using a hard-templating method, while a CMK-3 carbon (OMC) was also prepared for comparison. The capacitive performance of these two carbons was investigated in ionic liquid of EMImBF4 and EMImTSFI. As demonstrated by the structure analysis, BOMC possesses almost same surface area and pore size as OMC, while the former carbon possesses higher content of oxygen-containing groups. In ionic liquid electrolyte, the carbons mainly show typical electric double layer capacitance, and the capacitance retention ratio and ion diffusion of electrolyte is determined to the surface chemical property. BOMC present visible pseudo-capacitance due to the oxygenated groups in hydrophilic EMImBF4, while no visible pseudo-capacitive behavior was observed in hydrophobic EMImTSFI.

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34

Lim, June Sung, Jae Hyung Kim, Jinwoo Woo, Du San Baek, Young Jin Sa y Sang Hoon Joo. "Designing Highly Active Nanoporous Carbon Electrocatalysts for H₂O₂ Production Via Active Site Elucidation". ECS Meeting Abstracts MA2022-01, n.º 35 (7 de julio de 2022): 1497. http://dx.doi.org/10.1149/ma2022-01351497mtgabs.

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Fossil fuel-based hydrocarbon economy has invoked a serious climate change due to ever-increasing emission of CO2. In this regard, electrosynthesis has emerged as a promising route that enables the clean and continuous production of chemicals and fuels.[1] Electrochemical production of hydrogen peroxide (H2O2) via the two-electron (2e−) oxygen reduction reaction (ORR) can serve as a promising alternative for the currently prevailing anthraquinone process [1,2]. However, improving H2O2 selectivity remains one of important challenges in electrochemical H2O2 production because 2e− ORR competes with 4e− ORR, further reduction of H2O2 (2e−+2e− ORR), and H2O2 chemical disproportionation. Carbon nanomaterials have demonstrated promising performance for H2O2 production as low-cost electrocatalysts [3–5], however understanding of key structural factors and active sites is still lacking. In this work, we have prepared nanoporous carbon-based model catalysts and conducted a systematic study to identify the active oxygen functionality and carbon structure factor [6]. We have found that the carboxyl (O−C=O) groups located at the graphitic edge carbons are the major active sites for the electrosynthesis of H2O2 (Figure (a)). The best-performing carbon catalyst (O-GOMC-5.5) with abundant active oxygenated graphitic edge carbons exhibited the highest H2O2 production activity among the reported carbon-based catalysts (Figure (b)) and excellent long-term stability (168 h) with almost 100% of H2O2 faradaic efficiency. Figure 1

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35

Ma, Haiwen, Kunquan Li y Qiangfei Chai. "Chemical Modification of Bagasse-Based Mesoporous Carbons for Chromium(III) Ion Adsorption". Journal of Applied Biomaterials & Functional Materials 15, n.º 1_suppl (16 de junio de 2017): 52–61. http://dx.doi.org/10.5301/jabfm.5000358.

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Aims Modified bagasse-based mesoporous carbons were prepared for the efficient chromium(III) ion adsorption and removal from aqueous solutions. Methods Mesoporous carbons were prepared from bagasse with H3PO4 activation and subsequently oxidized with nitric acid and modified with ethylenediamine. Results The results showed that the modified carbon was rich in mesopores, oxygen and nitrogen-containing groups, and the Cr(III) adsorption capacity was greatly improved after modification, which was found to be higher than both pristine and oxidized carbons. The Cr(III) adsorption capacity on modified carbon was significantly influenced by the solution pH, and the optimum pH was 6 with the maximum Cr(III) adsorption capacity up to 24.61mg/g, which was almost 3 times higher than that for pristine carbon. Thermodynamic results manifested the adsorption was spontaneous and endothermic. Kinetic rates fitted the pseudo-second-order model very well. XPS study indicated the amino group was a key factor of the high efficient adsorption.

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36

Lu, Beihu, Jing Zhou, Yuqiao Song, Hailong Wang, Wei Xiao y Dihua Wang. "Molten-salt treatment of waste biomass for preparation of carbon with enhanced capacitive properties and electrocatalytic activity towards oxygen reduction". Faraday Discussions 190 (2016): 147–59. http://dx.doi.org/10.1039/c5fd00215j.

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Carbon powders are building blocks for electrochemical energy storage/conversion devices. Green, cost-affordable and facile preparation of carbon with applicable electrochemical properties is therefore essential for effective utilization of fluctuating renewable energy. Herein, the preparation of carbon nanoflakes via impregnation of waste biomass i.e. boiled coffee beans in molten Na₂CO₃–K₂CO₃ (with equal mass) at 800 °C and molten CaCl₂ at 850 °C is reported. The microstructure and surface chemistry of the obtained carbons are specified. The correlations between synthetic conditions and microstructure/surface chemistry of the obtained carbons are rationalized. The derived carbon nanosheets are tested and compared as active materials for supercapacitors in a configuration of symmetric full cells in 1 M MeEt₃NBF₄ in acetonitrile and electrocatalysts towards the oxygen reduction reaction (ORR) in O₂-saturated 0.1 M aqueous KOH. Despite the lower surface area, the carbon nanosheets derived in molten Na₂CO₃–K₂CO₃ exhibit enhanced capacitive properties and electrocatalytic ORR activity. The present study highlights the importance of thermal media on the microstructure, surface chemistry and electrochemistry of carbon from biomass.

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37

Anstice, P. J. C. y J. F. Alder. "The Effect of Sulphur Dioxide on the Adsorption Properties of Activated Carbon towards Chloropicrin". Adsorption Science & Technology 15, n.º 7 (julio de 1997): 541–50. http://dx.doi.org/10.1177/026361749701500707.

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Sulphur dioxide is believed to be adsorbed on activated carbons in both physically and chemically bound states. Sulphuric acid and a variety of oxygenated and hydrated sulphur oxide species are believed to be present on humidified carbons exposed to sulphur dioxide. Samples of ASC/T impregnated carbons were exposed to sulphur dioxide mixtures in humid air at 80% RG and 22°C. The sulphur dioxide-loaded carbons were then exposed to chloropicrin challenge at 5 mg/dm3 in air at 80% RH and 22°C and the chloropicrin breakthrough times measured. A relationship was found between the extra mass gain of the carbons (due to oxygen and water) with increasing sulphur dioxide loading, as predicted by other workers. The effect of sulphur dioxide loading on the chloropicrin breakthrough times was a gradual reduction to about one-third the time for unexposed carbon, with an adsorbed mass of sulphur dioxide equal to ca. 10% of the carbon mass in a 20 mm bed-depth filter.

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38

Singh, Madhu y Randy L. Vander Wal. "Carbon Composites—Graphene-Oxide-Catalyzed Sugar Graphitization". C 8, n.º 1 (14 de febrero de 2022): 15. http://dx.doi.org/10.3390/c8010015.

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Utilization of biopolymers to form graphitic carbons is challenged by their high oxygen content and resulting curved and defective carbon lamellae upon high-temperature heat-treatment. Two composites, one with graphene-oxide (GO) and the other with reduced graphene-oxide (rGO) as fillers, respectively, in a matrix of sugar, each for the same added 2.5 wt.%, exhibited different degrees of graphitization compared to pure sugar on its own. Reactive oxygen groups on GO contribute to reactive templating and crystallite formation. Under high-temperature heat-treatment, sugar, a well-known non-graphitizing precursor, is converted to graphitic carbon in the presence of GO. Possessing fewer oxygen groups, rGO forms two phases in the sugar matrix—a non-graphitic phase and a graphitic phase. The latter is attributed to the remaining oxygen on the rGO.

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39

Lei, Jie, Xiaodong Zhang, Zhenglin Zhou, Shaohui Fan, Bo Jiang y Xianlan Tian. "Experimental Study on the Treatment of 1, 4 butanediol Mixed Wastewater by Ferro-carbon Micro-electrolysis". E3S Web of Conferences 83 (2019): 01015. http://dx.doi.org/10.1051/e3sconf/20198301015.

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The mixed wastewater of 1, 4 butanediol was tested with iron filings and carbon powder as catalyst by aeration to provide oxygen. The effects of carbon powder, pH value and reaction time on wastewater treatment were studied. The optimal experimental condition was that the mesh number of activated carbons was 20, the pH value was 5, the reaction time was 30min, and the Chemical Oxygen Demand (COD) removal efficiency reached 36.2%. At the same time, The response surface method was used to analyze and optimize the experimental results, and the relation formula of each influencing factor on removal efficiency was established, and the order of influence degree of each factor on removal efficiency (pH> activated carbon mesh number > reaction time) was obtained, in which pH had the greatest influence on the treatment rate of ferro-carbon micro-electrolysis treatment of 1, 4-butanediol wastewater.

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40

Borkowski, Andrzej, Wojciech Kiciński, Mateusz Szala, Justyna Topolska, Paweł Działak y Marcin D. Syczewski. "Interactions of Fe–N–S Co-Doped Porous Carbons with Bacteria: Sorption Effect and Enzyme-Like Properties". Materials 13, n.º 17 (21 de agosto de 2020): 3707. http://dx.doi.org/10.3390/ma13173707.

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Carbon-based (nano)materials doped with transition metals, nitrogen and other heteroatoms are considered active heterogeneous catalysts in a wide range of chemical processes. Recently they have been scrutinized as artificial enzymes since they can catalyze proton-coupled electron transfer reactions vital for living organisms. Herein, interactions between Gram-positive and Gram-negative bacteria and either metal-free N and/or S doped or metal containing Fe–N–S co-doped porous carbons are studied. The Fe- and N-co-doped porous carbons (Fe–N–C) exhibit enhanced affinity toward bacteria as they show the highest adsorption capacity. Fe–N–C materials also show the strongest influence on the bacteria viability with visible toxic effect. Both types of bacteria studied reacted to the presence of Fe-doped carbons in a similar manner, showing a decrease in dehydrogenases activity in comparison to controls. The N-coordinated iron-doped carbons (Fe–N–C) may exhibit oxidase/peroxidase-like activity and activate O2 dissolved in the solution and/or oxygen-containing species released by the bacteria (e.g., H2O2) to yield highly bactericidal reactive oxygen species. As Fe/N/ and/or S-doped carbon materials efficiently adsorb bacteria exhibiting simultaneously antibacterial properties, they can be applied, inter alia, as microbiological filters with enhanced biofouling resistance.

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41

Phothong, Krittamet, Chaiyot Tangsathitkulchai y Panuwat Lawtae. "The Analysis of Pore Development and Formation of Surface Functional Groups in Bamboo-Based Activated Carbon during CO2 Activation". Molecules 26, n.º 18 (17 de septiembre de 2021): 5641. http://dx.doi.org/10.3390/molecules26185641.

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Pore development and the formation of oxygen functional groups were studied for activated carbon prepared from bamboo (Bambusa bambos) using a two-step activation with CO2, as functions of carbonization temperature and activation conditions (time and temperature). Results show that activated carbon produced from bamboo contains mostly micropores in the pore size range of 0.65 to 1.4 nm. All porous properties of activated carbons increased with the increase in the activation temperature over the range from 850 to 950 °C, but decreased in the temperature range of 950 to 1000 °C, due principally to the merging of neighboring pores. The increase in the activation time also increased the porous properties linearly from 60 to 90 min, which then dropped from 90 to 120 min. It was found that the carbonization temperature played an important role in determining the number and distribution of active sites for CO2 gasification during the activation process. Empirical equations were proposed to conveniently predict all important porous properties of the prepared activated carbons in terms of carbonization temperature and activation conditions. Oxygen functional groups formed during the carbonization and activation steps of activated carbon synthesis and their contents were dependent on the preparation conditions employed. Using Boehm’s titration technique, only phenolic and carboxylic groups were detected for the acid functional groups in both the chars and activated carbons in varying amounts. Empirical correlations were also developed to estimate the total contents of the acid and basic groups in activated carbons in terms of the carbonization temperature, activation time and temperature.

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42

Mirzaeian, Mojtaba, Qaisar Abbas, Michael R. C. Hunt y Peter Hall. "Pseudocapacitive Effect of Carbons Doped with Different Functional Groups as Electrode Materials for Electrochemical Capacitors". Energies 13, n.º 21 (26 de octubre de 2020): 5577. http://dx.doi.org/10.3390/en13215577.

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In this study, RF-based un-doped and nitrogen-doped aerogels were produced by polymerisation reaction between resorcinol and formaldehyde with sodium carbonate as catalyst and melamine as the nitrogen source. Carbon/activated carbon aerogels were obtained by carbonisation of the gels under inert atmosphere (Ar) followed by activation of the carbons under CO2 at 800 °C. The BET analysis of the samples showed a more than two-fold increase in the specific Surf. area and pore volume of carbon from 537 to 1333 m2g−1 and 0.242 to 0.671 cm3g−1 respectively after nitrogen doping and activation. SEM and XRD analysis of the samples revealed highly porous amorphous nanostructures with denser inter-particle cross-linked pathways for the activated nitrogen-doped carbon. The X-Ray Photoelectron Spectroscopy (XPS) results confirmed the presence of nitrogen and oxygen heteroatoms on the Surf. and within the carbon matrix where improvement in wettability with the drop in the contact angle from 123° to 80° was witnessed after oxygen and nitrogen doping. A steady drop in the equivalent series (RS) and charge transfer (RCT) resistances was observed by electrochemical measurements after the introduction of nitrogen and oxygen heteroatoms. The highest specific capacitance of 289 Fg−1 with the lowest values of 0.11 Ω and 0.02 Ω for RS and RCT was achieved for nitrogen and oxygen dual-doped activated carbon in line with its improved Surf. chemistry and wettability, and its enhanced conductivity due to denser inter-particle cross-linked pathways.

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43

Wu, Zhao, Xiaolong Xu, Jianchun Wang y Guangbin Dong. "Carbonyl 1,2-transposition through triflate-mediated α-amination". Science 374, n.º 6568 (5 de noviembre de 2021): 734–40. http://dx.doi.org/10.1126/science.abl7854.

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Careful choreography for a ketone shift Chemists devote tremendous effort to the precise placement of oxygens in molecular frameworks. Wu et al . report a convenient method to shift the oxygen in a carbonyl group to an adjacent carbon center. After activation of the oxygen to an alkenyl triflate, cooperative catalysis by palladium and norbornene adds nitrogen to the neighboring carbon while displacing the triflate with hydride. Hydrolysis then produces the desired shifted ketone. The protocol is well suited to late-stage variation of complex molecules during drug optimization. —JSY

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44

Bedia, Jorge, Manuel Peñas-Garzón, Almudena Gómez-Avilés, Juan J. Rodriguez y Carolina Belver. "Review on Activated Carbons by Chemical Activation with FeCl3". C — Journal of Carbon Research 6, n.º 2 (10 de abril de 2020): 21. http://dx.doi.org/10.3390/c6020021.

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This study reviews the most relevant results on the synthesis, characterization, and applications of activated carbons obtained by novel chemical activation with FeCl3. The text includes a description of the activation mechanism, which compromises three different stages: (1) intense de-polymerization of the carbon precursor (up to 300 °C), (2) devolatilization and formation of the inner porosity (between 300 and 700 °C), and (3) dehydrogenation of the fixed carbon structure (>700 °C). Among the different synthesis conditions, the activation temperature, and, to a lesser extent, the impregnation ratio (i.e., mass ratio of FeCl3 to carbon precursor), are the most relevant parameters controlling the final properties of the resulting activated carbons. The characteristics of the carbons in terms of porosity, surface chemistry, and magnetic properties are analyzed in detail. These carbons showed a well-developed porous texture mainly in the micropore size range, an acidic surface with an abundance of oxygen surface groups, and a superparamagnetic character due to the presence of well-distributed iron species. These properties convert these carbons into promising candidates for different applications. They are widely analyzed as adsorbents in aqueous phase applications due to their porosity, surface acidity, and ease of separation. The presence of stable and well-distributed iron species on the carbons’ surface makes them promising catalysts for different applications. Finally, the presence of iron compounds has been shown to improve the graphitization degree and conductivity of the carbons; these are consequently being analyzed in energy storage applications.

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45

Luo, Xianyou, Ping Yuan, Junhui Luo, Haoming Xiao, Junyi Li, Heng Zheng, Baodong Du, De Li y Yong Chen. "The Enhancing Effect of Stable Oxygen Functional Groups on Porous-Carbon-Supported Pt Catalysts for Alkaline Hydrogen Evolution". Nanomaterials 13, n.º 8 (20 de abril de 2023): 1415. http://dx.doi.org/10.3390/nano13081415.

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The oxygen functionalization of carbon materials has widely been employed to improve the catalytic performance of carbon-supported Pt (Pt/C) catalysts. Hydrochloric acid (HCl) has often been employed to clean carbons during the preparation of carbon materials. However, the effect of oxygen functionalization through a HCl treatment of porous carbon (PC) supports on the performance of the alkaline hydrogen evolution reaction (HER) has rarely been investigated. Herein, the impact of HCl combined with the heat treatment of PC supports on the HER performance of Pt/C catalysts has been comprehensively investigated. The structural characterizations revealed similar structures of pristine and modified PC. Nevertheless, the HCl treatment resulted in abundant hydroxyl and carboxyl groups and the further heat treatment formed thermally stable carbonyl and ether groups. Among the catalysts, Pt loading on the HCl-treated PC followed by a heat treatment at 700 °C (Pt/PC-H-700) exhibited elevated HER activity with a lower overpotential of 50 mV at 10 mA cm−2 when compared to the unmodified Pt/PC (89 mV). Pt/PC-H-700 also exhibited better durability than the Pt/PC. Overall, novel insights into the impact of the surface chemistry properties of porous carbon supports on the HER performance of Pt/C catalysts were provided, which were useful for highlighting the feasible improvement of HER performances by regulating the surface oxygen species of porous carbon supports.

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46

Villalgordo-Hernández, David, Aida Grau-Atienza, Antonio A. García-Marín, Enrique V. Ramos-Fernández y Javier Narciso. "Manufacture of Carbon Materials with High Nitrogen Content". Materials 15, n.º 7 (25 de marzo de 2022): 2415. http://dx.doi.org/10.3390/ma15072415.

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Nowadays one of the biggest challenges for carbon materials is their use in CO2 capture and their use as electrocatalysts in the oxygen reduction reaction (ORR). In both cases, it is necessary to dope the carbon with nitrogen species. Conventional methods to prepare nitrogen doped carbons such as melamine carbonization or NH3 treatment generate nitrogen doped carbons with insufficient nitrogen content. In the present research, a series of activated carbons derived from MOFs (ZIF-8, ZIF-67) are presented. Activated carbons have been prepared in a single step, by pyrolysis of the MOF in an inert atmosphere, between 600 and 1000 °C. The carbons have a nitrogen content up to 20 at.% and a surface area up to 1000 m2/g. The presence of this nitrogen as pyridine or pyrrolic groups, and as quaternary nitrogen are responsible for the great adsorption capacity of CO2, especially the first two. The presence of Zn and Co generates very different carbonaceous structures. Zn generates a greater porosity development, which makes the doped carbons ideal for CO2 capture. Co generates more graphitized doped carbons, which make them suitable for their use in electrochemistry.

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47

San-Pedro, Liliana, Roger Méndez-Novelo, Emanuel Hernández-Núñez, Manuel Flota-Bañuelos, Jorge Medina y Germán Giacomán-Vallejos. "Selection of the Activated Carbon Type for the Treatment of Landfill Leachate by Fenton-Adsorption Process". Molecules 25, n.º 13 (2 de julio de 2020): 3023. http://dx.doi.org/10.3390/molecules25133023.

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Sanitary landfill leachates usually have characteristics that depend on the region where they are generated and according to the age of the landfill, which is why a unique treatment for their sanitation has not been found. However, the adsorption preceded by the Fenton process has been proven to be highly efficient at removing contaminants. In this study, the adsorptive capacity of two types of activated carbon, granular and powdered, was analyzed to determine which was more efficient in the adsorption stage in the Fenton-adsorption process. Likewise, its behavior was analyzed using three isotherm models (Langmuir, Freundlich and Temkin), testing the raw leachate and the Fenton-treated one with both carbons. The adsorption that is carried out on the carbons is better adjusted to the Freundlich and Temkin models. It concludes that multilayers, through the physical adsorption, carry out the adsorption of pollutants on the surface of the carbons. The results show that, statistically, granular activated carbon is more efficient at removing chemical oxygen demand (COD), and powdered activated carbon removes color better. Finally, an adsorption column was designed for the Fenton-adsorption process that was able to remove 21.68 kgCOD/kg carbon. Removal efficiencies for color and COD were >99%.

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48

Thyssen, Niels y Mahlon G. Kelly. "Water-air exchange of carbon dioxide and oxygen in a river: Measurement and comparison of rates". Archiv für Hydrobiologie 105, n.º 2 (2 de mayo de 1989): 219–28. http://dx.doi.org/10.1127/archiv-hydrobiol/105/1989/219.

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49

Kiose, Tatyana, Tatyana Rakitskaya, Alim Ennan, Volodymyr Vasylechko y Halyna Gryshchouk. "Composition and Activity of Copper-Palladium Catalyst on Carbon Fiber Material for Air Purification from Carbon Monoxide". Chemistry & Chemical Technology 17, n.º 2 (1 de junio de 2023): 272–78. http://dx.doi.org/10.23939/chcht17.02.272.

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A set of research methods (X-ray phase, desorption, kinetic) was used to determine the state of the basic components K2PdCl4 and Cu(NO3)2 in the catalyst for the oxidation of carbon monoxide by oxygen. It was found that the palladium (II) and copper (II) initial compounds under the action of carbon fiber carrier change their state. Palladium is reduced to X-ray amorphous Pd0, and copper (II) is in the form of a crystalline phase Cu2(OH)3Cl. It was found that the catalyst exhibits protective properties within the initial concentrations of carbon monoxide  300 mg/m3 and an effective contact time of 0.45 s and can be used in human respiratory protection.

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50

Pipek, P., L. Staruch y M. Izumimoto. "Stabilization of minced meat colour by carbon monoxide". Czech Journal of Food Sciences 26, No. 5 (31 de octubre de 2008): 333–38. http://dx.doi.org/10.17221/1130-cjfs.

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The effect of carbon monoxide was studied on the colour stabilisation of minced meat and on oxidation of lipids. The meat colour was evaluated using reflectance spectrophotometry and video image analysis (software LUCIA 5.20). Minced meat (beef and mixture of beef and pork) was packed under industrial conditions into three different modified atmospheres (MA) consisting of combinations of oxygen, carbon dioxide, carbon monoxide, and nitrogen. Carbon monoxide prevented the oxidation of lipids and haem pigments in minced meat and thus stabilised the red colour of minced meat. The redness a* of the meat packed under CO was constant during storage (nearly a* = 20), whereas in MA containing oxygen this value decreased (a* = 5). The thiobarbituric acid reactant substances content rose in the samples packed under MA to 2 mg/kg, whereas in CO atmosphere it did not exceed 0.1 mg/kg.

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