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Activated Carbon (activated + carbon)
Kinds of Activated Carbon Selected AbstractsAddition of activated carbon to batch activated sludge reactors in the treatment of landfill leachate and domestic wastewaterJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 8 2001Özgür Akta Abstract Leachate from a municipal landfill was combined with domestic wastewater and was treated in batch activated sludge systems. The effectiveness and applicability of the addition of Powdered Activated Carbon (PAC) to activated sludge reactors was investigated. Isotherm tests were carried out with PAC in order to estimate the extent of adsorption of organic matter onto PAC. Then, in activated sludge reactors COD (Chemical Oxygen Demand) removal and nitrification were studied both in the absence and presence of PAC for comparison purposes. In both cases, Oxygen Uptake Rates (OUR) were measured with respect to time in order to investigate substrate removal and change in microbial activity. Addition of PAC to activated sludge increased COD removal by removing mainly the non-biodegradable fraction in leachate. The COD decreases in batch reactors were best expressed by a first-order kinetic model that incorporated this non-biodegradable leachate fraction. With added PAC, nitrification was also enhanced. But in all of the batch runs a significant accumulation of NO2 -N took place, indicating that the second step of nitrification was still inhibited. © 2001 Society of Chemical Industry [source] Effect of Activated Carbon Bed on Binder Removal from Ceramic Injection MoldingsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 3 2001Martin Trunec Weight losses during the binder removal from ceramic injection moldings that have been placed in beds of activated carbon powder and two types of alumina powder were compared. The effect of the specimen size and shape on debinding in a bed of activated carbon was investigated. Because of the structure of its particles, activated carbon powder allowed binder losses in ceramic moldings that consisted of submicrometer-sized particles to increase at a temperature of 130°C. The binder loss in a bed of activated carbon was dependent on the ratio of surface area to volume of the body that was extracted. Renewal of the sorption abilities of the bed of activated carbon after saturation with binder increased the rate of binder removal. [source] Activated Carbon as a Restoration Tool: Potential for Control of Invasive Plants in Abandoned Agricultural FieldsRESTORATION ECOLOGY, Issue 2 2006Andrew Kulmatiski Abstract Exotic plants have been found to use allelochemicals, positive plant,soil feedbacks, and high concentrations of soil nutrients to exercise a competitive advantage over native plants. Under laboratory conditions, activated carbon (AC) has shown the potential to reduce these advantages by sequestering organic compounds. It is not known, however, if AC can effectively sequester organics or reduce exotic plant growth under field conditions. On soils dominated by exotic plants, we found that AC additions (1% AC by mass in the top 10 cm of soil) reduced concentrations of extractable organic C and N and induced consistent changes in plant community composition. The cover of two dominant exotics, Bromus tectorum and Centaurea diffusa, decreased on AC plots compared to that on control plots (14,8% and 4,0.1%, respectively), and the cover of native perennial grasses increased on AC plots compared to that on control plots (1.4,3% cover). Despite promising responses to AC by these species, some exotic species responded positively to AC and some native species responded negatively to AC. Consequently, AC addition did not result in native plant communities similar to uninvaded sites, but AC did demonstrate potential as a soil-based exotic plant control tool, especially for B. tectorum and C. diffusa. [source] Surface-Treated Activated Carbon for Removal of Aromatic Compounds from WaterCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 5 2009B. Li Abstract Modifications of commercial activated carbons by chemical treatment with HNO3 or HCl and HF and the adsorption behavior of simple aromatic compounds (aniline, pyridine, phenol, and benzene) on activated carbon and modified activated carbon were investigated. The results show that the textural properties change a little after these modifications, but the surface acidity (mainly oxygen-containing groups) of activated carbon modified with HNO3 increases greatly. The effect of ash of activated carbon on adsorption of the organic compounds mentioned above is insignificant. However, addition of surface acidity (mainly surface oxygen-containing groups) decreases the adsorption capacity of compounds significantly. The adsorption uptake of compounds on activated carbon with oxidation of HNO3 is low possibly due to dispersive interaction, water cluster blocking, or competition between water and compounds adsorbed on activated carbon's surface because of hydrophilic increase of the activated carbon surface. The solubility of aromatic compounds in water has an important effect on the adsorption capacity of activated carbon. qm and KL (Langmuir adsorption parameters) for the aromatic compounds vary similarly. [source] Adsorption of SO2 on Activated Carbon for Low Gas ConcentrationsCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 5 2007P. Zhang Abstract Adsorption experiments of SO2 on activated carbon has been carried out for low concentrations (about 100,ppm) at room temperature (15 to 33,°C) with varying humidity in the air. The breakthrough curves show that at high relative humidity or relative higher SO2 concentration, the load capacity increases with respect to temperature. The humidity of the air is also of benefit to the load capacity of SO2. When an adsorption process is interrupted and the activated carbon is kept closed for a while, the SO2 concentration at the exit of a fixed-bed adsorber is similar to that of the fresh activated carbon and begins at a very low value. It appears that the sorption potential has been refreshed after the storage period. Analysis of desorption experiments by simultaneous thermal analysis combined with mass spectrometry (MS) after loading, shows that the physisorbed SO2 and H2O are desorbed at low temperatures. At higher temperatures, the MS peak of SO2 and H2O occur at the same time. Compared with desorption immediately after loading, after one day, the desorption peak due to the physisorbed SO2 disappears. From this, it can be concluded that the refreshment of the loading capacity of the activated carbon after storage is mainly due to a change in the nature of the SO2 from a physisorbed state to a chemisorbed form. The same mechanism leads to a continuous refreshment of the sorption potential by means of a chemical reaction during the adsorption process. [source] ChemInform Abstract: Lewis Acid or Broensted Acid Catalyzed Reactions of Vinylidene Cyclopropanes with Activated Carbon,Nitrogen, Nitrogen,Nitrogen, and Iodine,Nitrogen Double-Bond-Containing Compounds.CHEMINFORM, Issue 21 2009Jian-Mei Lu Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: Oxidation of Secondary Benzylic Alcohols to Ketones by Activated Carbon,Molecular Oxygen System.CHEMINFORM, Issue 18 2008Yuki Sano Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Direct and Practical Synthesis of 2-Arylbenzoxazoles Promoted by Activated Carbon.CHEMINFORM, Issue 5 2004Yuka Kawashita Abstract For Abstract see ChemInform Abstract in Full Text. [source] In situ Chemical Deposition of Polyaniline on Activated Carbon for Electrochemical CapacitorsCHINESE JOURNAL OF CHEMISTRY, Issue 1 2006Zhang-Hua Zhou Abstract Polyaniline (PA) film was chemically deposited onto the surface of activated carbon (AC) uniformly. Chemical deposition was carried out in 0.1 mol/L aniline plus 0.5 mol/L H2SO4 solution adopting V2O5·nH2O coated on the surface of activated carbon as oxidant. The surface morphologies and structures of the composite materials were characterized by scanning electron microscopy and FT-IR spectra. The electrochemical properties of the composite material electrodes were studied by cyclic voltammetry and constant current charge/discharge tests in 1 mol/L H2SO4 solutions. The specific capacitance of composite materials was exhibited as high as 237.5 F/g at a current density of 1.0 A/g compared with a value of 120 F/g for pure carbon electrode. Good power characteristic and good stability of composite electrodes were also demonstrated. [source] High Power Density Electric Double Layer Capacitor with Improved Activated CarbonCHINESE JOURNAL OF CHEMISTRY, Issue 2 2003Yang Hui Abstract The improvement on commercial activated carbon (AC) through the reactivation under steam in the presence of NiCl2 catalyst leads to the increases of both energy and power densities of electric double layer (dl) capacitors. When AC was treated at 875 °C for 1 h, its discharge specific capacitance increases up to 53.67 F· g,1, an increase of about 25% compared to the as-received AC. Moreover, a significant increase in high rate capability of electric dl capacitor was found after the improvements. Surprisingly, both the treated and untreated AC samples showed similar specific surface area and pore size distribution, but some changes in the surface groups and their concentrations after reactivation were verified by X-photoelectron spectra. Thus, it is reasonable to conclude that the decrease in the surface concentration of the carbonyl-containing species for the improved AC results in an increase of accessibility of the pores to the organic electrolyte ion, causing the enhancements of both the specific capacitance and high rate capability. [source] Clarification of date juiceINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 3 2003Mohamed A. Al-Farsi Summary This study was initiated to utilize a variety of low quality dates (Qish-Habash) so that high quality syrup could be produced by modifying the clarification process of the date juice. Five different clarification treatments were used: (1) filtration, (2) hot liming and filtration, (3) cold liming and filtration, (4) powder-activated carbon and filtration, and (5) granular-activated carbon and filtration. The sugar content, total soluble solids, total ash, pH, colour and purity were analysed to determine the clarification effects. The clarified juices produced by these treatments were evaporated under constant conditions to produce date syrup. Filtration, and activated carbon and filtration were the most successful treatments for the clarification of the date juice. Filtration gave the highest improvement in syrup purity (97.7%), due to the reduction of total ash by 19.5% and colour by 44.6%. Activated carbon removed the juice colour to give the lowest amount (60% in powder form and 57% in granular form), as well as reducing total ash, which led to an improved syrup purity, 92.2% in powder form and 91.4% in granular form. Liming clarification had undesirable effects, by increasing the total ash (15% in hot and 17% in cold lime), and increasing the colouring matter produced by decomposition. [source] Mineralization improvement of phenol aqueous solutions through heterogeneous catalytic ozonationJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 12 2003Fernando J Beltrán Abstract To assess the mineralization level achieved, aqueous solutions of phenol have been treated with ozone in the presence of different solid catalysts. Activated carbon was the principal catalyst investigated, although some additional experiments were carried out by utilizing metal oxide-based catalysts (ie Ti, Co and Fe) supported onto alumina. Usage of Co/Al2O3 led to the highest values of phenol byproduct mineralization, nevertheless some metal leaching was experienced in the process. The operating variables studied when using activated carbon as the catalyst were ozone gas concentration, amount of catalyst added and temperature. Regardless of the catalyst type used, two different ozonation kinetic regimes were observed: (I) an initial period, corresponding to the presence of phenol in solution, characterized by small amounts of dissolved ozone and no improvement of the mineralization degree if comparing catalytic and non-catalytic runs; (II) a second period, free of phenol, in which dissolved ozone accumulated in water and the beneficial effects of catalysts on mineralization were noticed. Experimental data also demonstrated the improvement in oxalic acid elimination in the presence of heterogeneous catalysts. Finally, consumption of ozone per mass of carbon removed, reaction factors and Hatta numbers were also calculated. Copyright © 2003 Society of Chemical Industry [source] Development of a 1-Methylcyclopropene (1-MCP) Sachet Release SystemJOURNAL OF FOOD SCIENCE, Issue 1 2006Younsuk S. Lee ABSTRACT The partitioning of 1-methylcyclopropene (1-MCP) between the gas/polymer matrix was determined for 2 adsorbing agents and 4 sachet materials to estimate the adsorption potential of 1-MCP at 23°C. The release study was performed using a closed system under 2 different environmental conditions, dry air (0% RH) and 90% RH. Sachets made from Tyvek®, paper, low-density polyethylene (LDPE), and polyvinyl acetate (PVA) materials were fabricated to contain silica gel and activated carbon. Activated carbon sachets did not release 1-MCP at either testing condition. Activated carbon had a very strong affinity for 1-MCP. The permeability coefficients of 1-MCP and water in polyethylene and polyvinyl acetate films were determined using a quasi-isostatic method. LDPE sachets containing silica gel had similar 1-MCP release rates at both 0% and 90% RH. PVA sachets containing silica gel had slow release of 1-MCP. The amount of 1-MCP released from PVA sachets containing silica gel at 90% RH was larger than the amount of 1-MCP released at 0% RH. Release of 1-MCP from paper and Tyvek sachets was largely dependent on the sorbate-absorbing ability of the adsorbing agents. [source] Equilibrium and kinetic study for the removal of malachite green using activated carbon prepared from Borassus flabellofer male flowerASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 3 2010P. E. Jagadeesh Babu Abstract Activated carbon was prepared from dried Borassus flabellofer male flower and batch adsorption experiments were conducted to study its potential to remove malachite green (MG) dye. The process was further optimized by studying the operating variables like initial pH of the stock solution, activation temperature, initial dye concentration, adsorbent loading and contact time. The optimized pH and activation temperatures were found to be 7.55 and 450 °C respectively, where further analysis was made using these optimal variables. Linear, Freundlich and Langmuir isotherms were studied and it was found that the Langmuir isotherms have the highest correlation coefficients compared to the others. Further, the sorption kinetics were analysed using pseudo-first-order and pseudo-second-order kinetic models. The data showed that the second-order equation was the more appropriate, which indicate that the intra-particle diffusion is the rate limiting factor. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source] DBD regeneration of GAC loaded with acid orange 7ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 5 2009Guang-Zhou Qu Abstract Activated carbon (AC) has been widely used as adsorbent in various industrial applications, such as purification of water in sewage facilities and filtration of air in toxicity-treating factories. However, after exhaustion, AC should be regenerated and reused because of the limited resources for AC production and additional secondary pollution of spent-carbon dumped into water or soil. In this study, a process for regenerating AC based on high active species (O3, ·OH, HO2, O2, ·RO, etc.) generated by dielectric barrier discharge (DBD) oxidation was proposed. The regeneration of granular-activated carbon (GAC) exhausted with azo dye acid orange 7 was investigated to assay this method. The influences of the parameters, such as treatment time, electric field and gas kind, on the readsorption rate were studied systematically. The results of structural properties of GAC analyses showed that the surface area, the micropore area, external surface area, micropore volume and total volume of GAC after three cycles DBD treatment decreased to different extent. The adsorption isotherms indicated that the regeneration efficiency was about 81% after three times DBD plasma regeneration cycles, which confirmed the reuse feasibility of the regenerated GAC. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source] Removal of pesticides from red and white wine by the use of fining and filter agentsAUSTRALIAN JOURNAL OF GRAPE AND WINE RESEARCH, Issue 1 2004GREG A. RUEDIGER Abstract Effects of the use of the fining and filtration agents, diatomaceous earth, bentonite, polyvinylpoly-pyrrolidone and activated carbon, on the removal of seven fungicides (carbendazim, chlorothalonil, fenarimol, metalaxyl, oxadixyl, procymidone and triadimenol) and three insecticides (carbaryl, chlorpyrifos and dicofol) from wines were investigated. Carbendazim was determined by high performance liquid chromatography (HPLC) after quantitative conversion into 2-aminobenzimidazole (2AB). The concentrations of all the other compounds in wine were quantified using a multi residue assay involving solid phase extraction (SPE) and gas chromatography-mass spectrometry (GC-MS). After treatment and processing, conducted under conditions simulating those that are typical in Australian commercial winemaking, the greatest reduction in concentration in all treatments was for chlorothalonil, chlorpyrifos and dicofol. There was a significant relationship between the extent of removal of each pesticide and its solubility in wine, such that the lower the solubility, the greater the extent of removal. Activated carbon had the largest effect on the removal of most pesticides, while bentonite had a major effect on the removal of carbendazim. For all compounds and agents, the rate of removal was greater in white wine than in red wine. [source] Comparison of Fixed and Fluidized Activated Carbon Beds for Removal of Organic VaporsCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 7 2004I.E. Agranovski Abstract Activated carbons are commonly used for removal of organic vapors from exhaust air streams. Two configurations, including fixed and fluidized carbon beds are usually employed in industry to meet various requirements of the industrial process which is being used. This paper investigates the performance of such configurations and provides a comparative analysis. It was found that for thin carbon layers, the fixed bed performs more efficiently with the difference exceeding 15,% for the layers with the thickness less than 15,mm. This difference is decreasing with increase of the layer thickness and becomes less than 5,% for the beds thicker than 100,mm. Considering various advantages of the fluidized beds over fixed beds, including lower resistance to the gas flow, excellent gas distribution and minimal possibility of clogging in case of existence of alien particles in the gas, they are recommended for use with the minimal thickness of the layer to be larger than 100,mm. [source] Mercury binding on activated carbonENVIRONMENTAL PROGRESS & SUSTAINABLE ENERGY, Issue 4 2006Bihter Padak Abstract Density functional theory has been employed for the modeling of activated carbon (AC) using a fused-benzene ring cluster approach. Oxygen functional groups have been investigated for their promotion of effective elemental mercury binding on AC surface sites. Lactone and carbonyl functional groups yield the highest mercury binding energies. Further, the addition of halogen atoms has been considered to the modeled surface, and has been found to increase the AC's mercury adsorption capacity. The mercury binding energies increase with the addition of the following halogen atoms, F > Cl > Br > I, with the fluorine addition being the most promising halogen for increasing mercury adsorption. © 2006 American Institute of Chemical Engineers Environ Prog, 2006 [source] Improved methods for carbon adsorption studies for water and wastewater treatmentENVIRONMENTAL PROGRESS & SUSTAINABLE ENERGY, Issue 2 2006Wei-chi Ying Abstract An improved method was developed to rank activated carbon in removing organic water pollutants. The simple and standardized evaluation method uses a set of four adsorptive capacity indicators: phenol, iodine, methylene blue, and tannic acid numbers; those four indicator compounds were selected because they cover the molecular size range of most organic water pollutants. An improved microcolumn rapid breakthrough (MCRB) test method was developed from the existing HPMC (high-pressure minicolumn) and RSSCT (rapid small-scale column test) methods by simplifying the experimental procedure and using readily available low-cost pump, sampler, piping, and fittings. This method can be practiced in an ordinary environmental laboratory to select the best carbon, to verify the treatment effectiveness, and to estimate the adsorption treatment cost based on the observed capacity utilization rate for carbon in the adsorber without the problems often encountered with using small and mini traditional columns. The benefits of the four-parameter carbon selection method and the MCRB method were demonstrated by adsorption isotherm and breakthrough data for several indicator compounds and organic water pollutants. These improved methods will enable efficient carbon adsorption studies necessary for more applications of carbon adsorption technology in water and wastewater treatment. © 2006 American Institute of Chemical Engineers Environ Prog, 2006 [source] A new morphospecies of Microcystis sp. forming bloom in the Cheffia dam (Algeria): Seasonal variation of microcystin concentrations in raw water and their removal in a full-scale treatment plantENVIRONMENTAL TOXICOLOGY, Issue 4 2007Hichèm Nasri Abstract Toxic cyanobacterial blooms are an increasing problem in Algeria. The production of cyanotoxins (microcystins) and their presence in drinking water represent growing hazards to human health. In this study, seasonal variations in the concentrations of total microcystins and physicochemical parameters (pH, temperature, dissolved oxygen, nitrate, orthophosphate, and chlorophyll- a) were analyzed in the Cheffia dam (Algeria), mainly used to supply drinking water. The removal of cyanobacterial cells and microcystins was also evaluated in full-scale plant associated with the Cheffia reservoir. The levels of microcystins (MCYSTs) in both raw and drinking water were evaluated using the protein phosphatase type 2A (PP2A) inhibition test as MCYST-LR equivalents. Identification of microcystin variants was achieved by LC/MS/MS. During the period of study (March,December 2004), microscopic observation showed the dominance in the autumn months (September,November) of a new morphospecies of Microcystis sp. The MCYST-LR equivalent concentrations in raw water varied between 50.8 and 28,886 ng L,1. The highest level of toxins was observed in October 2004 and was significantly correlated with the chlorophyll- a. Three variants of microcystins assigned as microcystin-YR (MCYST-YR), microcystin-LR (MCYST-LR), and 6Z -Adda stereoisomer of MCYST-LR were observed in the crude extract of the Microcystis sp. bloom sample. During the bloom period, total elimination of Microcystis sp. and toxins were achieved through a classical treatment plant comprised of coagulation and flocculation, powdered activated carbon at 15 mg L,1, slow sand filtration and chlorination before storage. © 2007 Wiley Periodicals, Inc. Environ Toxicol 22: 347,356, 2007. [source] Evaluation of sorbent amendments for in situ remediation of metal-contaminated sedimentsENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 9 2010Seokjoon Kwon Abstract The present study evaluated sorbent amendments for in situ remediation of sediments contaminated with two divalent metals. A literature review screening was performed to identify low-cost natural mineral-based metal sorbents and high-performance commercial sorbents that were carried forward into laboratory experiments. Aqueous phase metal sorptivity of the selected sorbents was evaluated because dissolved metals in sediment porewater constitute an important route of exposure to benthic organisms. Based on pH-edge sorption test results, natural sorbents were eliminated due to inferior performance. The potential as in situ sediment amendment was explored by comparing the sorption properties of the engineered amendments in freshwater and saltwater (10 PPT salinity estuarine water) matrices. Self-assembled monolayers on mesoporous supports with thiols (Thiol-SAMMSÔ) and a titanosilicate mineral (ATSÔ) demonstrated the highest sorption capacity for cadmium (Cd) and lead (Pb), respectively. Sequential extraction tests conducted after mixing engineered sorbents with contaminated sediment demonstrated transfer of metal contaminants from a weakly bound state to a more strongly bound state. Biouptake of Cd in a freshwater oligochaete was reduced by 98% after 5-d contact of sediment with 4% Thiol-SAMMS and sorbed Cd was not bioavailable. While treatment with ATS reduced the small easily extractable portion of Pb in the sediment, the change in biouptake of Pb was not significant because most of the native lead was strongly bound. The selected sorbents added to sediments at a dose of 5% were mostly nontoxic to a range of sensitive freshwater and estuarine benthic organisms. Metal sorbent amendments in conjunction with activated carbon have the potential to simultaneously reduce metal and hydrophobic contaminant bioavailability in sediments. Environ. Toxicol. Chem. 2010;29:1883,1892. © 2010 SETAC [source] Bioaccumulation of native polycyclic aromatic hydrocarbons from sediment by a polychaete and a gastropod: Freely dissolved concentrations and activated carbon amendmentENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 9 2006Gerard Cornelissen Abstract The present paper describes a study on the bioaccumulation of native polycyclic aromatic hydrocarbons (PAHs) from three harbors in Norway using the polychaete Nereis diversicolor and the gastropod Hinia reticulata. First, biota,sediment accumulation factors (BSAFs) were measured in laboratory bioassays using the original sediments. Median BSAFs were 0.004 to 0.01 kg organic carbon/kg lipid (10 PAHs and 6 organism,sediment combinations), which was a factor of 89 to 240 below the theoretical BSAF based on total sediment contents (which is approximately one). However, if BSAFs were calculated on the basis of measured freely dissolved PAH concentrations in the pore water (measured with polyoxymethylene passive samplers), it appeared that these BSAFfree values agreed well with the measured BSAFs, within a factor of 1.7 to 4.3 (median values for 10 PAHs and six organism,sediment combinations). This means that for bioaccumulation, freely dissolved pore-water concentrations appear to be a much better measure than total sediment contents. Second, we tested the effect of 2% (of sediment dry wt) activated carbon (AC) amendments on BSAF. The BSAFs were significantly reduced by a factor of six to seven for N. diversicolor in two sediments (i.e., two of six organism,sediment combinations), whereas no significant reduction was observed for H. reticulata. This implies that either site-specific evaluations of AC amendment are necessary, using several site-relevant benthic organisms, or that the physiology of H. reticulata caused artifactually high BSAF values in the presence of AC. [source] Effects of dose and particle size on activated carbon treatment to sequester polychlorinated biphenyls and polycyclic aromatic hydrocarbons in marine sedimentsENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 7 2005John R. Zimmerman Abstract Recent laboratory studies show that mixing activated carbon with contaminated sediment reduces the chemical and biological availability of hydrophobic organic contaminants. In this study, we test the effects of varying the activated carbon dose and particle size in reducing the aqueous availability of polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) and the uptake of PCBs by two benthic organisms. We mixed PCB- and PAH-contaminated sediment from Hunters Point Naval Shipyard, San Francisco Bay (CA, USA), for one month with activated carbon, at doses of 0.34, 1.7, and 3.4% dry mass basis. We found that increasing the carbon dose increased the effectiveness in reducing PCB bioaccumulation. In 56-d uptake tests with the benthic organisms Neanthes arenaceodentata and Leptocheirus plumulosus, PCB bioaccumulation was reduced by 93 and 90%, respectively, with 3.4% carbon. Increasing the dose also increased the effectiveness in reducing PCB and PAH aqueous concentrations and uptake by semipermeable membrane devices and quiescent flux of PCBs to overlying water. Decreasing activated carbon particle size increased treatment effectiveness in reducing PCB aqueous concentration, and larger-sized activated carbon (400,1,700 ,m) was ineffective with a contact period of one month. We invoke a numerical model based on intraparticle diffusion in sediment and activated carbon particles to help interpret our experimental results. This model was useful in explaining the trends for the effect of activated carbon dose and particle size on PCB aqueous concentrations in well-mixed systems. [source] Optimization of activated carbon-based decontamination of fish oil by response surface methodologyEUROPEAN JOURNAL OF LIPID SCIENCE AND TECHNOLOGY, Issue 7 2007Åge Oterhals Abstract The effect of activated carbon (AC) adsorption on the reduction of persistent organic pollutants (POP) in fish oil was studied based on response surface methodology at a 5-g/kg AC inclusion level. Pretreatment of the oil by alkali refining and bleaching increased the POP levels. The tested process variables (contact time and temperature) affected the AC adsorption rate and significant first- and second-order response models could be established. Polychlorinated dibenzo- p -dioxins and dibenzofurans (PCDD/F) showed a very rapid adsorption behavior and the concentration and toxic equivalent (TEQ) level could be reduced by 99%. Adsorption of dioxin-like polychlorinated biphenyls (DL-PCB) was less effective and depended on ortho substitution, i.e. non- ortho PCB were adsorbed more effectively than mono- ortho PCB with a maximum of 87 and 21% reduction, respectively, corresponding to a DL-PCB-TEQ reduction of 73%. A common optimum for both PCDD/F and DL-PCB adsorption could not be identified. AC treatment had no effect on the level of polybrominated diphenyl ether flame retardants. The differences in adsorption patterns may be explained based on molecular conformation. No change in oil quality could be observed based on oxidation parameters. Compliance with present PCDD/F and DL-PCB legislation levels in fish oil can be achieved based on AC adsorption. [source] Compact and Light Supercapacitor Electrodes from a Surface-Only Solid by Opened Carbon Nanotubes with 2,200 m2 g,1 Surface AreaADVANCED FUNCTIONAL MATERIALS, Issue 3 2010Tatsuki Hiraoka Abstract An approach is presented to make a "surface-only solid" with a surface area of 2,240,m2 g,1 (1,310,m2,cm,3), corresponding to 85% of the atoms constituting a surface, by opening single-walled carbon nanotube forests and solids via controlled oxidation. The controllability of the approach is demonstrated by tailoring the hole size to match the guest molecule, for example, nitrogen, fullerene, or solvated ions. These features make the surface-only solid an ideal vessel for material and energy storage, as demonstrated by its use for electrodes to realize a light and compact supercapacitor with high energy (24.7,W h kg,1) and power (98.9,kW kg,1) densities, exceeding those of activated carbon (16.9,W h kg,1 and 35.7,kW kg,1). [source] Use of liquid chromatography,tandem mass spectrometry for quantitative analysis of clopyralid in compost and forageGRASSLAND SCIENCE, Issue 3 2009Ryuichi Uegaki Abstract In this study, we first developed a technique to quantify clopyralid using liquid chromatography,tandem mass spectrometry (LC/MS/MS) and tested its performance for compost and corn plant samples. Then, we measured the uptake of clopyralid by forage corn grown on two types of soil mixed with clopyralid-contaminated compost, in order to investigate the potential of ingestion of compost clopyralid by animals through forage crops. Because of the high recovery ratios (80,82% for compost and 98% for corn), sufficient theoretical quantification limits (5.0 and 1.7 ,g kg,1 fresh matter, respectively) and close agreement with the bioassay method (73 ,g kg,1 for LC/MS/MS and 80 ,g kg,1 for bioassay), the LC/MS/MS method was considered to be of potential value for determining clopyralid in compost and plant materials. Corn plants took up clopyralid from soil (compost), with the amount and rate of uptake varying with soil types and application of activated carbon to soil. There is a need for quantifying clopyralid uptake by a range of forage crops under a range of cultivation conditions (e.g. climate, soil, management) to estimate clopyralid fluxes through the manure,forage,animal,manure pathway. [source] An Evaluation of Physicochemical Treatment Technologies for Water Contaminated with MTBEGROUND WATER MONITORING & REMEDIATION, Issue 4 2000Arturo A. Keller Treatment of methyl tertiary-butyl ether (MTBE) from contaminated surface and ground water supplies presents specific challenges due to the physicochemical properties of MTBE that depend strongly on its hydrophilic nature, and translate into a high solubility in water, and low Henry's constant and low affinity for common adsorbents. We evaluate four treatment technologies-air stripping, granular activated carbon (GAC), hydrophobic hollow fiber membranes, and advanced oxidation processes (AOP)-using ozone or ozone/hydrogen peroxide. Experimental work was carried out to generate parameter values necessary for the design of these processes. Ten different flow rates/concentration combinations were evaluated in our designs to cover the range from high flow rate/low concentration typical of surface water and ground water drinking water supplies to low flow rate/high concentration typical of ground water remediation sites. For all cases, the processes were designed to produce effluent water of 5 ,g/L or less. Capital costs and operation and maintenance costs were determined at the feasibility level by using standard engineering estimating practices. Air stripping is the lowest cost technology for high flow rales (100 to 1000 gpm) if no air treatment is required. Hollow fiber membranes are the lowest cost technology for flow rates of 10 to 100 gpm if no air treatment is required, which is typical at these low flow rates. GAC will be most costeffective at all flow rates if air treatment is required and the influent water has low levels of other organic compounds. AOP using ozone or ozone/hydrogen peroxide is in all cases more expensive than the alternative technologies, and there are sufficient uncertainties at this point with respect to byproducts of AOP to warrant further study of this technology. The cost of treating MTBE-contaminated water for conventional technologies such as air stripping and GAC is 40% to 80% higher than treating water contaminated only with other hydrocarbons such as benzene. [source] Modeling and CFD prediction for diffusion and adsorption within room with various adsorption isothermsINDOOR AIR, Issue 2003S. Murakami Abstract This paper presents physical models that are used for analyzing numerically the transportation of volatile organic compounds (VOCs) from building materials in a room. The models are based on fundamental physicochemical principles of their diffusion and adsorption/desorption (hereafter simply sorption) both in building materials and in room air. The performance of the proposed physical models is examined numerically in a test room with a technique supported by computational fluid dynamics (CFD). Two building materials are used in this study. One is a VOC emitting material for which the emission rate is mainly controlled by the internal diffusion of the material. The other is an adsorptive material that has no VOC source. It affects the room air concentration of VOCs with its sorption process. The floor is covered with an emission material made of polypropylene styrene,butadiene rubber (SBR). An adsorbent material made of coal-based activated carbon is spread over the sidewalls. The results of numerical prediction show that the physical models and their numerical simulations explain well the mechanism of the transportation of VOCs in a room. [source] Novel One-Step Synthesis of Porous-Supported Catalysts by Activated-Carbon Templating,ADVANCED MATERIALS, Issue 9 2006J. Blanco A new, simple, versatile, and easily scaleable one-step preparation method , an impregnated carbon procedure (ICP) , is proposed to produce highly dispersed active phases on supports of tailored porosity (see scheme; AC: activated carbon). This one-step synthesis unites simplicity of preparation with outstanding properties of the final catalysts and offers an interesting pathway towards industrial-catalyst manufacture. [source] Performance analysis of a modified two-bed solar-adsorption air-conditioning systemINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 7 2009K. Sumathy Abstract This paper presents the description and operation of a solar-powered modified two-bed adsorption air-conditioning system with activated carbon and methanol as the working pair. A simple lumped parameter model is established to investigate the performance of this continuous adsorption cycle consisting of a twin adsorber immersed in water tanks, which is measured in terms of the temperature histories, gross solar coefficient of performance and specific cooling power. In addition, the influence of some important design and operational parameters on the performance of the system has been studied. Compared with the conventional system, it is found that the modified system can operate more cycles and at a higher efficiency. The parametric study also shows that the adsorbent mass and the solar collector area have significant effect on the system performance as well as on the system size. Finally, when the system uses gas heater as an auxiliary heat source, it is found that the system can provide a stable cooling effect for a longer period of operation. Copyright © 2008 John Wiley & Sons, Ltd. [source] | |||||||||||||||||||||||||||||||||||||