Activated Carbon Felt Research Articles

Experimental study of the immobilization of Acidithiobacillus ferrooxidans on carbon based supports

The effect of graphite surface roughness on the immobilization of Acidithiobacillus ferrooxidans was studied. It was found that the most appropriate surface roughness was obtained by polishing graphite discs with 1500 grit polishing paper. After 24 h of inoculation this roughness had coverage of 25 × 10 3 cells/mm 2. The effects of different types of activated carbon fibers (felt versus fabric; both silicated and non-silicated) on the immobilization of A. ferrooxidans were also experimentally studied. In non-silicated samples the activated carbon fiber support with the greatest surface area per gram (felt) lead to the greatest number of immobilized microorganisms over a 12 h period (29 × 10 3 cells/mm 2). The addition of SiO 2 particles to the activated carbon fiber supports considerably enhanced cell adhesion on both activated carbon felt and fabric. Furthermore, the silicated felt exhibited the greatest number of immobilized A. ferrooxidans cells of all activated carbon fiber preparations studied (36 × 10 3 cells/mm 2).

Adsorption of Toluene onto Activated Carbon Fibre Cloths and Felts: Application to Indoor Air Treatment

Due to their bad effects on human health, removing Volatile Organic Compounds from indoor air has become an issue of major interest. In this study, the potential use of six commercial activated carbon felts and cloths for indoor toluene removal was investigated. Both batch and dynamic adsorption studies were performed, at toluene concentrations ranging from 21 to 18160 mg m−3, for an air velocity representative of indoor air treatment (0.37 m s−1). Batch measurements showed that felts exhibited higher adsorption capacities at equilibrium than cloths at high toluene concentrations, whereas this trend may be inverted at low concentrations. Experimental isotherms and kinetics were satisfactorily fitted by the Langmuir-Freundlich model and the Linear Driving Force model respectively. No main differences between the adsorption kinetics of felts and cloths were reported. Dynamic adsorption capacities at saturation appeared to be higher than 120 mg g−1 for both cloths and felts, irrespective of relative humidity levels and toluene concentrations. The influence of relative humidity on the adsorption capacity of felts was not significant for the higher toluene concentration studied in dynamics (307 mg m−3), whereas an increase in relative humidity induced a decrease in adsorption capacity at the lower toluene concentration (38 mg m−3). Moreover, experimental curves of breakthrough time versus thickness of medium were satisfactorily fitted by the Adams-Bohart model, and the critical thickness determined by this model appeared to be below 1.3 mm, regardless of the medium or toluene concentration.

Study of the performance of Pt catalysts supported on activated carbon felt and granular carbon for nitrobenzene hydrogenation

Abstract The catalytic behavior of the Pt (1 wt%) catalysts supported on purified activated carbon felt (ACF) and powder carbon (C) has been studied in the nitrobenzene (NBZ) hydrogenation reaction in liquid phase after activation under a H 2 atmosphere between 298 and 623 K. Hydrogen chemisorption measurements, temperature-programmed reduction (TPR) and X-ray photoelectron spectroscopy (XPS) were used to characterize the metallic phase of the catalysts. For Pt/ACF catalysts, the catalytic activity in nitrobenzene hydrogenation after reduction at 298 K was very high and it decreased as the reduction temperature increased up to 373 K. On the other hand, the Pt/C catalyst after reduction at 298 K was inactive. The activity of the Pt/C catalysts increased in a moderate way when the reduction temperature increases up to 373 K. Between 373 and 623 K of reduction temperature, the hydrogenation rate was modified in a minor proportion for both catalysts. The Pt/ACF catalyst previously reduced at 298 K showed a lag step before the reaction ignition. This effect could be attributed to the tendency the metallic centers have to conform the proper arrangement to hydrogenate the nitrobenzene molecule.

Study on a Novel Material Technology for Chemical/Biological Protection

A novel chemical/biological (CB) protective material was studied in this paper. The material was designed to provide protective properties and satisfactory wearing comfort. In the fabric construction, a PET fabric was laminated with modified PTFE membrane by paste dot coating, and then coated by PU solution in a direct process. Finally, it was laminated with active carbon felt. The modified PTFE membrane completely prevents permeation of the mustard liquid and biological warfare agent, any residuals penetrating the PU will be absorbed by active carbon felt. Furthermore, the CB protective material can provide satisfactory wearing comfort.

Electrosorption of thiocyanate anions on active carbon felt electrode in dilute solution

Adsorption and electrosorption of thiocyanate (SCN −) anions on active carbon felt electrodes were measured by UV spectroscopy and cyclic voltammetry to provide more knowledge of the application of electrosorption on high-area carbon material in industrial waste water purification. Positive polarization caused increased adsorption of SCN −. SCN − showed the highest electrosorption capacity at about pH 3. Reversible electrosorption of SCN − to different extents was observed by changing the direction of polarization currents, which is possibly accompanied by the accessible surface area of C-felt being increased by positive polarization and electrochemical oxidation of SCN −. The enhanced capacity for adsorption by positive polarization will improve reuse of active carbon felt.

Oxygen functional groups involved in the styrene production reaction detected by quasi in situ XPS

In this work, the oxidative dehydrogenation (ODH) of ethylbenzene to styrene reaction over an activated carbon felt was studied by experiments of mass spectrometry coupled to a quasi in situ XPS system. These experiments permit to deepen into the mechanism of the aforementioned reaction. The results obtained allow us to conclude that carbonyl-quinone and hydroxyl groups are involved in the ODH. The amount of both types of oxygen groups increases when the ethylbenzene conversion to styrene increases. Therefore, the reaction seems to take place through the carbonyl-quinone/hydroxyl and styrene/ethylbenzene redox couples, confirming that carbonyl-quinone are the active phase in this oxidative dehydrogenation.

Catalytic performance in citral hydrogenation and characterization of PtSn catalysts supported on activated carbon felt and powder

The liquid phase citral hydrogenation carried out at 70 °C and atmospheric pressure over Pt and PtSn catalysts supported on both activated carbon powder (C) and felt (ACf), was investigated. It was found that the addition of Sn to the Pt catalysts increases the reaction rate of the citral hydrogenation, this influence being more important for carbon-based catalysts. Besides, the Sn addition sharply enhances the selectivity to double unsaturated alcohols (nerol and geraniol) for both catalyst series. The secondary products were the unsaturated aldehyde (citronellal), the single-unsaturated alcohol (citronellol) and the cyclization products (isopulegol and menthol). The performance of these catalysts in the citral hydrogenation was related with the characteristics of the metallic phase, which were determined by test reactions of the metallic phase (cyclohexane dehydrogenation and cyclopentane hydrogenolysis), H 2 chemisorption, TPR and XPS in order to postulate the models of the metallic surface. In this sense, a fraction of ionic Sn (detected by XPS) would be deposited near Pt aggregates, thus enhancing the polarization of the carbonyl group of the citral molecule, and leading to an increase in the selectivity to nerol and geraniol. This effect appears to be different depending on the support type.

Monitoring for N,N-dimethylformamide and N,N-dimethylacetamide with a diffusive sampler using distilled water as an absorbent.

To obtain an appropriate sampling method for evaluating individual workers' exposure concentrations to chemicals highly soluble in water, the suitability of LiPS (liquid passive sampler) as diffusive sampler was examined. Although adsorbed chemical substances with activated carbon felt being used as the adsorbent must be desorbed in such samplers, this process can be omitted by using liquid as the absorbent. This kind of simplification can be utilized for water-soluble solvents such as N,N-dimethylformamide (DMF) and N,N-dimethylacetamide (DMAC). In laboratory experiments DMF and DMAC levels determined by this method were sufficiently correlated with exposure concentrations, exposure duration, and cumulative exposure levels. The sampling rates for DMF and DMAC obtained from these results were 0.50 and 0.43 mL/min, respectively, and the theoretical sampling rate for DMF obtained using Fick's diffusion formula was consistent with the experimental value. The effects of relative humidity, wind velocity, and temperature on the measured values were negligible within the range expected in a practical industrial environment. In a field survey the exposure concentrations for 38 workers handling DMF in the process of manufacturing spandex fiber and polyurethane gloves were determined both by this method and by the National Institute of Occupational Safety and Health (NIOSH) method, in which silica gel tubes are used. The DMF concentrations detected by the two methods were comparable (Y = 0.912X, correlation coefficient: 0.932). This LiPS method proved to be useful in determining the concentrations of DMF and DMAC to which workers were exposed.

Preparation of Pt catalysts supported on activated carbon felts (ACF)

Activated carbon felts (ACFs) have been used as supports for Pt catalysts. The preparation was carried out by the impregnation method using chloroplatinic acid as metal precursor. The effect of impregnation time and surface chemistry of the support on the catalytic properties and the characteristics of the metallic phase have been investigated. Nitrobenzene (Nbz) hydrogenation in liquid phase at 25 °C and cyclohexane (CH) dehydrogenation in gas phase at 300 °C were used as catalytic tests. The state of platinum in reduced catalysts (at 100 and 350 °C) was studied by TPR and XPS. Oxygen surface groups only produce a slight effect on the catalytic properties. The use of low impregnation times (30 min) during the preparation of Pt/ACF leads to catalysts with Pt mainly deposited in the outer shell of the fibers, while at higher impregnation times, the metallic atoms seem to be deposited inside the pores. Pt(0) species appear in catalysts reduced at 100 °C by effect of the reducing properties of the carbon fiber exhibiting a considerable catalytic activity for Nbz hydrogenation.

Electrochemical reduction of nickel ions from dilute artificial solutions in a GBC reactor

Reduction of chromate in very low concentration (20 ppm) has been carried out in a GBC reactor. Final concentrations below 0.5 ppm have been achieved at reasonable reaction rates. Spontaneous reduction of chromate by hydrogen in a GBC reactor without an external power source requires careful selection of cathode material. Chemically stable materials such as titanium and RVC tend to passivate when in contact with chromate solution and are unsuitable for use as cathode materials. Graphite, active carbon and graphite felt show no obvious passivation. Reduction of oxidized groups and oxygen are the major side reactions. These occur significantly, especially when using an activated carbon bed as a cathode.

Evaluation of an Activated Carbon Felt Passive Sampler in Monitoring Organic Vapors.

Using an activated carbon felt (ACF, KF-1600), the applicability of an ACF passive sampler in monitoring organic vapors was evaluated. The evaluated results of the ACF passive sampler were compared with those of a 3 M (Model 3500) passive sampler. At low-humidity condition (8 +/- 3% RH), the sampling rates of the ACF passive sampler for volatile organic vapors were within the range of +/-25% from the results of a charcoal tube, which was the reference method recommended by NIOSH. However, at high humidity condition (90 +/- 5% RH), even though the sampling rates for toluene, MIBK, and PCE were within the range of +/-25%, the sampling rates of ACF sampler for n-hexane and MEK decreased steeply with time after being high at the beginning of the exposure time. Under this condition, the sampling rate of the 3 M passive sampler for MEK was also high at the beginning of the exposure time. In case of the ACF passive sampler, the sampling rates of the relatively strong adsorbates such as toluene, MIBK, and PCE were much less affected by humidity than those of n-hexane and MEK which were weak adsorbates.

Adsorption equilibria of two halogenated carbons on a carbon fiber

Chlorofluorocarbons (CFCs) are presently considered to be the prime contribution to stratospheric ozone depletion. In this study, a microporous activated carbon felt (KF-1500) was used as a useful adsorbent for adsorption of trichlorofluoromethane and methylene chloride. The isotherms of these organic vapors on a microporous carbon felt were measured and the equilibrium parameters based on Dubinin-Radushkevich correlation were evaluated. Besides, the isosteric heats of adsorption were evaluated from the equilibrium data. It was found that equilibrium data for this carbon felt were well described by Dubinin-Radushkevich correlation.

Applicability of activated carbon felt to the dosimetry of solvent vapor mixture.

Affirmative results were obtained to prove that diffusion-absorption on carbon-desorption dosimetry is applicable to monitor exposure to mixed vapors of organic solvents (n-hexane:ethyl acetate:toluene=1:4:1). While most of seven carbon felt preparations tested failed to absorb n-hexane in humid air or the amounts absorbed were no longer proportional to vapor concentrations even in dry air when the sum of the three vapor concentrations were over 3 times workroom threshold limits, two preparations revealed capacity to absorb n-hexane even in the air with relative humidity of 95%. Furthermore, the amounts absorbed during four hour exposures were linearly related to the vapor concentrations of at least 4.5 times workroom threshold limits when the three vapor concentrations were summed up, and, at lower concentrations, the absorbed amounts were proportional to the exposure duration of up to eight hours. Short term peak exposure could also be detected; the ratio between the observed and the expected was about 80% at lowest.