Sorption of volatile organic compounds on typical carpet fibers

Measurements of adsorption isotherms for three volatile organic compounds (VOCs) (toluene, 1,2-dichlorobenzene and 1,1,1-trichloroethane) on polyacrylonitrile carpet fibers over the temperature range 25-45 degrees C were carried out in a thermogravimetric analyzer (TGA). Linear isotherms were observed in all cases with values of the Henry coefficient ranging from 0.063 to 0.941 mm. The results of additional experiments carried out in a simple test chamber containing a single source of VOC showed that the carpet fibers acted as a significant sink causing a prolonged elevation of VOC concentration in the air within the chamber. An unsteady-state model is presented, which adequately described the adsorption and desorption phenomena occurring in the test chamber and yielded realistic values of the adsorption and desorption rate constants. There was good agreement between the equilibrium and kinetic constants obtained in the TGA and test chamber experiments.     

Assessment of the global fallout of plutonium isotopes and americium-241 in the soil of the central region of Saudi Arabia

A radiochemical technique for determination of plutonium isotopes and 241Am in soil samples is tested against IAEA-standard reference materials to determine its accuracy and precision for reliable results. The technique is then used in the investigation of topsoil samples, collected from the natural environment of the central region of Saudi Arabia, to assess the effect of fallout accumulation of these radionuclides in the region. Plutonium and americium were sequentially separated from all other components of the sample by anion-exchange chromatography and co-precipitated with Nd3+ as fluorides. The precipitates were mounted on membrane filters and measured using a high-resolution alpha-spectrometer. The results of the analysis of the reference materials showed satisfactory sensitivity and precision of the technique. The results of the analyzed soil samples show activity levels ranging from < LLD to 0.089 and from 相似文献