Charcoal coefficients

The accuracy of the measurement of radon concentrations with bare track detectors was found to be unsatisfactory due mainly to the changes of the deposition rate of radon progeny onto the detector as a result of air turbulence. In this work, therefore, a method was developed which can correct the contributions of the deposition to the track densities by classifying the etched tracks according to their appearance, i.e. round or wedge shaped. Using this method, about 30% improvement in the error of measurements was achieved. The calibration coefficient ob tained by experiment was 0.00424 tracks/cm /h/(Bq/m ), which agreed well with the calculated value. Comparison was also made of the present method with other passive methods, charcoal and Terradex, as to their performance under the same atmosphere. 

In order to assess the accuracy of the present method, we compared it with two other methods. One was the Track Etch detector manufactured by the Terradex Corp. (type SF). Simultaneous measurements with our detectors and the Terradex detectors in 207 locations were made over 10 months. The correlation coefficient between radon concentrations derived from these methods was 0.875, but the mean value by the Terradex method was about twice that by our detectors. The other method used was the passive integrated detector using activated charcoal which is in a canister (Iwata, 1986). After 24 hour exposure, the amount of radon absorbed in the charcoal was measured with Nal (Tl) scintillation counter. The method was calibrated with the grab sampling method using activated charcoal in the coolant and cross-calibrated with other methods. Measurements for comparison with the bare track detector were made in 57 indoor locations. The correlation coefficient between the results by the two methods was 0.323. In the case of comparisons in five locations where frequent measurements with the charcoal method were made or where the radon concentration was approximately constant, the correlation coefficient was 0.996 and mean value by the charcoal method was higher by only 12% than that by the present method. 

Adsorption Coefficient for Various Radon Adsorbing Charcoals... 

The dynamic adsorption coefficient can be used to gauge the performance of a charcoal bed under various conditions. 

Carbon type Given a fixed set of conditions (ie. flow rate, temperature, mass of charcoal, humidity) the type of carbon demonstrating the highest dynamic adsorption coefficient will be identified. 

Contaminants Indoor contaminants are expected to compete for adsorption sites on the charcoal. We will experimentally find the effect that these contaminants have on the dynamic adsorption coefficient and on the life-time of the charcoal bed. Since the number of radon atoms in even the most seriously contaminated houses is very small, decay product buildup is not expected to pose a significant problem. 

Figure 5. Median jump frequencies (Sr ) 1 for water adsorbed on NaX to saturation, for water on charcoal at saturation, and that expected for bulk water (from NMR relaxation times) dashed curve marked diff diffusion coefficients by magnetic field gradient technique normalized to (Sr) 1 by choice of jump distance of 2.7 A + dielectric relaxation times of Jansen...

The experiments were done at 70, 100, and 130°C and at pressures somewhat lower than atmospheric. Under these conditions reaction (368) is practically irreversible. Activated charcoal of the trademark Bayer AKT-4 ground to grain size 0.25-0.5 mm served as a catalyst. Estimation of the efficiency factor on the basis of the determination of the effective difusion coefficient of hydrogen in nitrogen or helium has shown that for this grain size the results of reaction rate measurements refer to the kinetic region. Estimation of relaxation time of the reaction rate from (67) showed the reaction to be quasi-steady at the condition of our experiments in the closed system. 

The affinity that the solvent vapor has for the activated charcoal or the charcoal s adsorptivity is reflected in the "collection" efficiency. Early studies(i> 2) show that for many solvents, collection efficiencies are similar. No generalization is without exception and therefore test atmospheres should be generated where this information is important. The collection efficiency and desorption efficiency, together with the analytical precision and accuracy are incorporated into the total coefficient of variation for the method. Many solvent vapor sampling methods are not this thoroughly documented in the literature because of the difficulty of generating known test atmospheres. In this study both direct injection and flowing of vapor-air mixtures over the charcoal were used for efficiency determinations these values are reported in table 1 and required much time and effort to obtain. 

Recrystallization of 6-nitroBIPS and its simple (methoxy, lower alkyl, halogen) substituted derivatives is often best carried out from pure ethyl acetate (i.e., free of ethanol and acetic acid) with use of decolorizing charcoal. Most dyes have a large temperature coefficient of solubility and crystallize beautifully. 

This technique enables gases to be separated by the selective adsorption of one or more from a mixture on a suitable packing in a column. The adsorbed gas, should that be required, may be subsequently recovered by elution or other means. Though only partially successful when applied to the isotopes of neon because the difference in their adsorption coefficient on charcoal is small, the method has enabled deuterium to be separated from a 1 1 deuterium-hydrogen mixture (Glucckauf and Kitt, 1956). The... 

The kinetics of the reaction have been investigated , and it is therefore possible to determine atomic hydrogen concentrations from the rate at which ortho-H.2 appears in a system initially containing only para-H2. Ortho-para hydrogen ratios may be determined by vapour phase chromatography using charcoal columns , and this technique probably replaces the earlier thermal conductivity measurements (for a description of the latter see ref. 220). The rate coefficients of reaction (23) cannot be fitfed to a simple Arrhenius expression Schulz and LeRoy find that their results can be expressed by... 

The carbon nanostructured support provides both a high activity and a high selectivity when compared to what is usually observed on traditional supports such as alumina or activated charcoal. Such catalytic behavior is attributed to the presence of a peculiar electronic interaction between the carbon nanofilaments and the metal which constitutes the active phase. This leads to a metallic site with unexpected catalytic performances [6,7]. In addition, due to their small dimensions, typically of about hundred of nanometers or less, the carbon nanofilaments display an extremely high external surface area which makes them a catalyst support of choice for liquid phase reactions. Due to the low difiusion coefficients of gaseous reactants in liquids, mass transfer phenomena become predominant in the liquid phase. The l%h external surfece area considerably decreases the... 

The preceding discussion emphasizes the applicability of Eq. (6-6) for adsorption onto polar adsorbents, particularly adsorbent samples deactivated by varying amounts of water. However, the derivation of Eq. (6-6) does not preclude its application to nonpolar adsorbents. Claesson has in fact observed 14) the existence of a similar relationship for adsorption onto various charcoals. For the homologous carboxylic acids as samples and ethanol as solvent, the Langmuir isotherm [Eq. (3.6-)] was found to describe the adsorption of each acid. The derived values of the Langmuir coefficient k [or K° in Eq. (3-6)] could be expressed as a function of the number n of carbon atoms in the sample molecule ... 

The partition coefficient is affected by temperature, pH and the type of activated charcoal used. 

Sudha et al. (2008) and Dinesh Karthik et al. (2009) reported on the removal of heavy metal cadmium and chrominm from industrial wastewater using chitosan-coated coconut charcoal and chitosan impregnated polyurethane foam, respectively. Adsorption and determination of metal ions such as zinc (11) and vanadium (II) onto chitosan from seawater have been studied (Muzzarelli et al. 1970, Muzzarelli and Sipos 1971, Muzzarelli and Rocchetti 1974). Adsorption of strontium (II), cobalt (11), zinc (11), and iron (III) on chitosan from sodium chloride solution have been reported (Nishimura et al. 1995). Adsorption behavior of Cu (II) (Minamisawa et al. 1996, Wu et al. 2000) and cobalt (11) (Minamisawa et al. 1999) were investigated. The amount of cadmium removed by chitin increases with increase of these parameters at a specific time. The application to experimental results of the Langmuir and Freundlich models shows that the Langmuir model gives a better correlation coefficient. 

---