Use Of Carbon Research Articles

Carbon-based novel sorbent for removing gas-phase mercury

The purpose of the present study is to develop a carbon-based sorbent for removing gaseous mercury. Existing commercial activated carbon for removing mercury is superior in efficiency but expensive. This study attempted to develop a cost-effective sorbent using petroleum coke, which is low-priced carbon source. It took note that the sulfur content of domestic petroleum coke is around 7%. Sulfur is a superior reaction material in removing mercury and it has been usually impregnated into activated carbon for use. Sulfur in petroleum coke is strongly stuck to carbon matrix, so it is not reactive as itself. This study applied high-temperature pyrolysis to petroleum coke to make its sulfur take out of the surface of the petroleum coke and used the sulfur in removing mercury. According to the result of the experiment, the specific surface area of petroleum coke increased around 10 times in the course of pyrolysis and the efficiency of mercury removal was significantly improved as part of sulfur taken out. Thus, pyrolyzed petroleum coke was considered to have high potential as a sorbent for removing mercury.

Assessing the in vitro biocompatibility of a novel carbon device for the treatment of sepsis

The aim of the present study was to conduct a preliminary investigation into the blood biocompatibility of a novel, uncoated carbon for use in a filtration/adsorption device for the treatment of sepsis. Carbon well prototypes were manufactured from phenol–formaldehyde–aniline-based pyrolysed carbons using monolithic polymer technology. Inflammatory blood cell and plasma protein mediation of the inflammatory response were evaluated using the novel carbon prototypes and compared with dialyser membrane and tissue culture plate controls. Assays determining monocyte and granulocyte adhesion, platelet adhesion and activation, granulocyte activation and complement activation were performed. Preliminary findings suggest an adsorptive but passivating carbon surface. Moderate levels of monocyte and granulocytes adhesion were seen in conjunction with adsorption of plasma proteins to the carbon surface. Activation of granulocyte and adherent platelets was not detected and the complement cascade was not activated by the carbons, indicating a surface compatible with blood contact. The results support the further development of the proposed carbon-based device for the treatment of sepsis.

Improvement of Commercial Active Carbon for Use in an Adsorption Cooling System

Of the various gas/solid adsorption processes, the adsorption of methanol on active carbon seems to be most interesting for use in thermodynamic systems such as heat pumps and transformers, as well as in cooling systems. The porous structures of two series of active carbons modified by the successive removal of the external layers from the particle surface, one by abrasion in a spouted bed and the other by subsequent demineralization of the abraded particles, were evaluated on the basis of nitrogen and methanol adsorption data. The porous structure parameters for these two sorbate series agreed reasonably well and allowed the D–R approach to be usefully applied for the characterization of these systems. The methods for calculating the heat effects associated with methanol adsorption over wide ranges of temperature and pressure are discussed.

Experimental design to optimize preparation of activated carbons for use in water treatment.

A series of seven activated carbons was obtained for use in drinking water treatments by steam-activation of olive-waste cakes. This raw material is an abundant and cheap waste byproduct of oil production, making these activated carbons economically feasible. The activated carbons, prepared by the one step method, were characterized, and the evolution of their characteristics (yield, adsorption capacities, and porosity) was analyzed as a function of the experimental parameters (activation temperature and activation time), using the Doehlert matrix. The Doehlert matrix allows the response surface to be studied with a good quality parameter estimation of the quadratic model. Each response has been described by a second order model that was adequate to predict responses in all experimental regions. The coefficients of the postulated model were calculated from the experimental responses by means of least squares regression, using the NEMROD software. We determined the region in which the optimum values of both activation temperature and activation time were achieved for the preparation of activated carbons suitable for use in water treatments. The "optimal activated carbon" was experimentally obtained, and its characteristic parameters showed a good agreement with those calculated from the model. The results obtained for activated carbons prepared by the one-step method were compared with those for activated carbons prepared by the two-step method. The characteristics of activated carbons obtained by the one-step and two-step methods showed that "one-step" activated carbons have a highly developed porous texture formed mainly of large macropores and micropores, whereas "two-step" activated carbons have a predominance of mesopores and narrow micropores. These activated carbons from olive-waste cakes showed a high capacity to adsorb herbicides (2,4-dichlorophenoxyacetic acid, 2,4-D; and 2-methyl, 4-chlorophenoxyacetic acid, MCPA) from water, with adsorption capacity values higher than those corresponding to a commercial activated carbon used from drinking water treatments.

A comparative study of carbons for use as an electrically conducting additive in the manganese dioxide cathode of an electrochemical cell

using continuous carbon-fiber carbon-matrix and polymer– untreated fibers are used. The activation treatment does not matrix composites. Comp Part B: Eng 1999;30(3):227–31. degrade the tensile properties of the fibers. [3] Sau KP, Chaki TK, Chakraborty A, Khastgir D. Electromagnetic interference shielding by carbon black and carbon fibre filled rubber composites. Plastics Rubber Comp Process Acknowledgements Appl 1997;26(7):291–7. [4] Ramadin Y, Jawad SA, Musameh SM, Ahmad M, Zihlif AM, Technical assistance by Weiming Lu of this University Paesano A et al. Electrical and electromagnetic shielding is appreciated. behavior of laminated epoxy–carbon fiber composite. Polymer Int 1994;34(2):145–50. [5] Huang CY, Pai JF. Studies on processing parameters and thermal stability of ENCF/ABS composites for EMI shieldReferences ing. J Appl Polym Sci 1997;63(1):115–23. [6] Shui X, Chung DDL. Submicron diameter nickel filaments [1] Chung DDL. Materials for electromagnetic interference and their polymer–matrix composites. J Mater Sci shielding. J Mater Eng Perform 2000;9(3):350–4. 2000;35:1773–85. [2] Luo X, Chung DDL. Electromagnetic interference shielding

Preparation of carbonaceous adsorbents for removal of chloroform from drinking water

Microporous carbons for use as adsorbents in removing chloroform from drinking water were prepared by activating charcoals made from the following natural raw materials: evergreen oak ( Q. phillyraeoides), bamboo ( P. pubescens), coconut shell ( C. nucifera), and Japanese cedar ( C. japonica), and from dehydrochlorinated vinylidene film. Chloroform adsorption was found to be enhanced by increase in the specific surface area of the microporous carbon, but suppressed by enlargement of micropore-size. This suppression is due to a decrease in the interaction, governed by London dispersion force, between the chloroform molecules and the pore walls of the microporous carbon. Carbon with iodine adsorption capacity of around 760 mg g −1 demonstrated the greatest chloroform adsorption regardless of the raw material used. In order of chloroform adsorption amount, the materials ranked as follows: vinylidene film>Japanese cedar>coconut shell≒evergreen oak>bamboo. The carbon produced by 30 min dehydrochlorination of vinylidene film and that produced by 50 min steam activation of Japanese cedar charcoal demonstrated adsorption capacities several times higher than that of commercial activated carbon.

Attainment of the Theoretical Yield of Carbon from Biomass

Previous work has shown that very high yields of charcoal are obtained when pyrolysis of the biomass feedstock is conducted at elevated pressure in a closed vessel, wherein the pyrolytic vapors are held captive and in contact with the solid products of pyrolysis. In this paper, we show that, for some biomass species, the yield of carbon produced by this process effectively attains the theoretical value predicted to exist when thermochemical equilibrium is realized. Various agricultural wastes (e.g., kukui nut, macadamia nut, and pecan shells) and tropical species (e.g., eucalyptus, leucaena, and bamboo) offer higher yields of carbon than the hardwoods traditionally employed by industry in the U.S. and Europe. Moreover, the yields of carbon from oat and rice hulls and from sunflower seed hulls are nearly as high as the yields of carbon from hardwoods. There is a correlation between the yield of carbon and the acid-insoluble lignin content of the feed. Charcoal briquettes made from agricultural wastes and lump charcoal from tropical species are promising sources of renewable carbon for use in the smelting of metal ores.

Chars Pyrolyzed from Oil Palm Wastes for Activated Carbon Preparation

Chars pyrolyzed from extracted oil palm fibers for the preparation of activated carbons were studied. The effects of pyrolysis temperature and hold time on density, porosity, yield, BET and micropore surface areas, total pore volume, and pore size distributions of chars were investigated. The optimum conditions for pyrolysis were found to be at a pyrolysis temperature of 850°C for a hold time of 3.5 h. Scanning electron micrographs of the char surfaces verified the presence of porosities. The experimental results showed that it was feasible to produce chars with high BET and micropore surface areas from extracted oil palm fibers. The resulting chars will be subjected to steam or carbon dioxide activation to prepare activated carbons for use as gas adsorbents for air pollution control.

Phenolic-resin-derived activated carbons

A novel binderless preparative route is described for the production of phenolic-resin-derived carbons for use as catalyst supports and adsorbents. The carbons can be produced in a wide variety of physical forms ranging from simple granules to large monolithic structures. The fully interconnected macropore structure of the carbons, which derives from the interconnected voids between the primary resin particles, can be precisely controlled to give a mean macropore size of between around 1 and 50 microns. This then gives rise to very high permeabilities that can be orders of magnitude higher than conventional porous support materials. The microstructure of the carbons appears to derive from the void spaces between small (∼4 nm) spherical resin domains generated during the initial polymer curing step which gives rise to a very narrow pore distribution with a mean pore size of ≈0.8 nm. This is in contrast to earlier studies that suggested the pores reflected voids in a tangled ribbon structure. The high purity of the carbons (total metals content of <500 ppm) has also allowed a precise determination of the activation kinetics. This has shown that the as-produced carbon comprises two domains – a low reactivity skeleton formed from the small resin domains, and a higher reactivity carbon that appears to partially fill the skeletal pore structure and that is selectively removed during activation.

Potential of agricultural by-product-based activated carbons for use in raw sugar decolourisation

The physical (bulk density and hardness) and chemical (pH and mineral content) characteristics of granular activated carbons (GACs) made from rice straw, pecan shells and hulls of soybean and rice were determined. The adsorption properties (iodine test, molasses test and raw sugar decolourisation efficiency) of these by-product-based carbons were also evaluated. A commercial decolourising carbon (Calgon CPG LF) was used as a comparison. Pecan-based carbons had bulk densities and hardness numbers higher than Calgon CPG LF. They also showed a mineral content and pH similar to or lower than the commercial carbon. The adsorption properties of the pecan-based carbons were, however, about 40% below that of the reference carbon. In contrast, rice (hull and straw)-based carbons exhibited good adsorption properties similar to the reference carbon in both iodine test and molasses test, but their ash content and their inherent pHs were higher than Calgon CPG LF. Both types of rice-based carbons were also more friable and had lower bulk densities than the commercial carbon. However, rice-hull-based carbon was statistically as effective as Calgon CPG-LF in decolourising raw sugar solutions at the 5% confidence level. Of the by-product-based carbons evaluated, pecan-shell-based GACs would be most suitable as raw sugar decolourisers if their adsorption efficiencies could be improved. © 1997 SCI.

5498493 Electron acceptor substituted carbons for use as anodes in rechargeable lithium batteries

A battery using carbonaceous materials with a graphite or disordered graphite structure wherein boron atoms are substituted for carbon atoms in the structure. The electrochemical potential of the carbonaceous materials is shifted as a result of such substitution, and the electrochemical capacity is increased. Both effects are desirable for anode materials in lithium ion type batteries.

Serological Determination of Nitrobacter Species in a Deodorizing Granular Activated Carbon Filter

Immunofluorescence is used to detect, to study species diversity and to count the nitrifying bacteria in a deodorization system for air polluted by ammonia. This process consists of the elimination of ammonia by a biological filter packed with granular activated carbon seeded with activated sludge enriched in nitrifying bacteria. Four serotypes are used, to treat Nitrobacter strains Ag, LL, W and X14. The serotypes are distributed in the same proportions throughout the filter, with the total bacteria count more concentrated near the gas source. This procedure is attractive but the count obtained is incomplete because there is no serotype for the Nitrobacter genera nor correlation between serotypes and genomic groups. Only serotypes prepared against isolated strains are known. It would therefore be interesting in a future study to isolate strains which have already colonized granular activated carbon for use in diversity studies. Another interesting avenue would be a total count of all Nitrobacter bacteria present.

Surface Analysis of Porous Carbon Microelectrodes with an Adsorbed Osmium Complex as a Mediator.

Many different forms of carbon have been used for preparing chemically modified electrodes with electrontransfer mediators. In previous reports, we described porous carbon microelectrodes (PCMEs) developed as enzyme sensors.'-3 A platinum disk electrode packed with a porous carbon material supported in osmium complex ([Os(bpy)3]2+I3+) as a redox electron transfer mediator and enzyme. The PCME surface was modified by a Nafion solution. The osmium complex was adsorbed on the PCME dipped in the osmium complex+ 10 mM LiC104 (M=mol dm-3) solution. The osmium complex was electrostatically adsorbed onto the Nafion region on the porous carbon. The construction of the PCME surface with the Nafion and osmium complex is important for the performance of an enzyme sensor. It is of considerable interest to examine how the osmium complex interacts with a modified carbon surface, because the adsorption of this mediator is crucial to the operation and lifetime of an enzyme sensor.'-3 However, there have been few reports concerning surface analyses of PCME with an adsorbed osmium complex. In this paper we discuss the depth distribution of Nafion and an osmium complex on a porous carbon surface using X-ray photoelectron spectroscopy (XPS), and the determined amount of the osmium complex on the PCME by means of chronocoulometry. described.)-3 The platinum microelectrode (diameter, 20 μm) was etched in hot aqua regia (80° C,1 h) to create a cavity; this cavity was then packed with a porous carbon material. To load the osmium complex onto the surface, the PCME was first immersed in a 2.5% Nafion solution (Aldrich) for 24 h in order to impart a negative charge onto the surface. The PCME was dipped into a 0.1 mM [Os(bpy)3] (PF6)2+10 mM LiC104 solution for 24 h. [Os(bpy)3] (PF6)2 (bpy: 2,2'-bipyridine) was synthesized from osmium(III) trichloride (Aldrich).6 All of the other chemicals used were of analytical grade. The buffer solution used was a mixture of 0.2 M disodium hydrogenphosphate and 0.1 M citric acid for pH 8.0. All of the electrochemical experiments were performed using a Bioanalytical System Electrochemical Analyzer (BASl00B/W) with a three-electrode system. An Ag/ AgCI reference electrode and a Pt counter electrode were placed in the cell. The surface modification of sheets of porous carbon for use in XPS followed the same treatments as those mentioned above. The XPS spectra were acquired using a Shimadzu ESCA 1000A instrument and Mg-Ku radiation.

Optimizing Pyrolysis of Sugar Carbons for Use as Anode Materials in Lithium‐Ion Batteries

Table sugar was pyrolyzed under various conditions. Carbons of pyrolyzed sugar demonstrated high capacity for Li intercalation, exceeding that of graphite. Experiments were carried out to search for optimal pyrolyzing conditions. The electrochemical behavior of these carbons was found to depend on the pyrolysis temperature, heating rate, argon gas flow rate, and morphology of the precursors. Pyrolysis of sugar was also carried out under vacuum, which is equivalent to a high argon gas flow. Carbons of pyrolyzed sugar under optimal conditions showed large reversible capacity, ≈650 mAh/g, small irreversible capacity, ⩽170 mAh/g, and small hysteresis between discharge and charge in carbon/Li metal electrochemical test cells. Pyrolyzed sugar carbons are therefore potential candidates as anode materials in Li‐ion batteries.

Carbon Isotopic Composition of Deep Carbon Gases in an Ombrogenous Peatland, Northwestern Ontario, Canada

Radiocarbon dating and carbon isotope analyses of deep peat and gases in a small ombrogenous peatland in northwestern Ontario reveals the presence of old gases at depth that are 1000–2000 yr younger than the enclosing peat. We suggest that the most likely explanation to account for this age discrepancy is the downward movement by advection of younger dissolved organic carbon for use by fermentation and methanogens bacteria. This study identifies a potentially large supply of old carbon gases in peatlands that should be considered in global carbon models of the terrestrial biosphere.

Development of a sensor for the detection of nitrite using a glassy carbon electrode modified with the electrocatalyst [Os(bipy) 2(PVP) 10Cl]Cl

The electrocatalytic polymer [Os(bipy) 2(PVP) 10Cl]Cl, where bipy = 2,2′-bipyridyl and PVP = poly(4-vinylpyridine), was used to modify glassy carbon for use in planar flow cells and conventional electrochemical cells for the reductive electrochemical detection of nitrite. The electrocatalyst accelerates a slow electrochemical reduction of nitrite via a two-step reduction process resulting in a 70-fold increase in response compared with the unmodified electrode. The detector response was evaluated with regard to flow-rate, applied potential, electrolyte pH and surface coverage of the polymer film. A mechanism for the two-step reduction process is proposed. The detector response appears to be limited by the rate constant of the mediated electrochemical reaction. A linear response range extending from 5 × 10 −6 to 1 × 10 −2 M nitrite was obtained, with a detection limit of 0.23 ng ml −1 for the planar flow cell and 0.23 ng ml −1 for a conventional electrochemical cell. The performance of the sensor was assessed with respect to stability, selectivity and interference. The sensor was applied to the determination of nitrite in saliva.

Development of an enzyme substrate incorporating semiconducting amorphous carbons for use in biosensors

Carbonaceous materials formed by the thermal decomposition of sulphanilic acid in the temperature range 700–1400 K are being studied for their potential as enzyme supports and electron mediators in biosensors. These carbons have been formulated into cylindrical pellets. Chemical analyses for the functional groups have established the presence of carboxylic, phenolic, lactonic and quinolic surface acidic oxides. This assignment is supported by infrared and electron spectroscopy. The enzyme glucose oxidase has been immobilised to carboxylic residues in the pellets via the carbodiimide method, with up to 8 × 10 −2 units of enzyme immobilised per cm 2 of the pellet (geometric area). Electrochemical investigations of the pellets have shown that the potential of the 1400 K electrode varies with pH showing approximately Nernstian behaviour. Cyclic voltammetry in 1 m sulphuric acid with these carbon pellets, shows the existence of a single oxidation/reduction peak on carbons prepared above 1000 K. The nature of the group/redox couple responsible for this peak is not yet certain.

Synthesis of optically active cyphenothrin-14C. 14C-labelling at the carbonyl carbon.

Optically active cyphenothrins, a-cyano-3-phenoxybenzyl (1R) -cis- and (1R) -trans-chrysan-themates were labelled with 14C at the carbonyl carbon for use in metabolic studies. Ethyl glycinate-1-14C hydrochloride (6), prepared from potassium cyanide-14C (2) in the three steps, was condensed with 2, 5-dimethyl-2, 4-hexadiene via the diazo intermediate to give ethyl cis, trans-chrysanthemate-14C (7) . Hydrolysis of the ester 7 followed by geometrical separation gave cis-and trans-chrysanthemic-14C acid (8a and 8b) . Each geometrical isomer (8a or 8b), was optically resolved to afford (1R) -cis- or (1R) -trans-chrysanthemic-14C acid (8c or 8d) . Esterification of 8c and 8d with a-cyano-3-phenoxybenzyl bromide (9) gave (1R) -cis-and (1R) -trans-eyphenothrin- (carbonyl-14C) (la and 1b) in the yields of 4 and 6% from 2, respectively.

Synthesis of optically active cyphenothrin-14C. 14C-labelling at the cyano and the benzyl carbons.

Optically active cyphenothrins, a-cyano-3-phenoxybenzyl (1R) -cis- and (1R) -trans-chrysan-themates, were labelled with 14C independently at the cyano and the benzyl carbons for use in metabolic studies, α-Cyano-14C-3-phenoxybenzyl alcohol (4) prepared from potassium cyanide-14C (2) was condensed with (1R) -cis- or (1R) -trans-chrysanthemoyl chloride (5a or 5b) to give (1R) -cis- or (1R) -trans-cyphenothrin- (cyano-14C) (la or 1b) in the yield of 82 or 95% from 2, respectively. Similarly, a-cyano-3-phenoxybenzyl-a-14C alcohol (12), which was synthesized from barium carbonate-14C (6) in four steps, was esteri feed with 5a or 5b to afford (1R) -cis- or (1R) -trans-cyphenothrin- (benzyl-14C) (lc or id) . The overall yields of 1c and 1d were 61 and 69% from 6, respectively.

Performance of catalytically condensed carbon for use in accelerator mass spectrometry

Two catalytic processes have been explored for the preparation of suitable samples for use in 14C measurements on an accelerator mass spectrometer. A heavy hydrocarbon was condensed from C 2H 2 using AlBr 3 as a catalyst. This process had low isotopic fractionation, and the carbon ion beam obtainable was 60–70% that from graphite. In the second process, iron powder was used to produce graphite directly from CO 2 and H 2 at 600 °C. A sample preparation system using this reaction has been built. The carbon product produces exceptionally intense, long-lived ion beams. The process introduces little 14C background, and has no observed memory effects.