Evaluation of activated carbon fibers (ACF) for removal of volatile organic compounds (VOCs) in indoor environments
The purpose of this research was to address the applicability of activated carbon fiber (ACF) for removal of VOCs in indoor environments. Adsorption isotherms were characterized in both the passive mode (without air drawn through the ACF specimen) and the active mode (with air penetrating through the ACF specimen) at various concentrations for acetone, toluene and limonene and three species of ACF. The Langmuir, Freundlich and Dubinin-Redushkevich models were used to predict adsorption capacities at untested concentrations for the three adsorbates and three ACF adsorbers in the both passive and active modes. Empirical statistical models based on the Freundlich equation were then established and evaluated by comparisons made between experimental results and predicted results for trichloroethylene and methyl ethyl ketone. Sorption experiments were performed in order to determine the sorptive kinetics of ACF, cotton, polyester, gypsum board, carpet and empty chamber surfaces for acetone, toluene and limonene. Tested VOC adsorption rates and adsorption capacities on ACF are greater than tested indoor sink materials by a factor of 1 to 3 orders of magnitude in the 10 to 1000 mg/m3 concentration range and by a factor of 3 to 6 orders of magnitude in the 0.01 to 10 mg/m 3 concentration range, respectively. The linear Langmuir sink model was examined for indoor sink materials and found to be applicable, while the non-linear sink model was successfully applied for ACF, with the assumption that the adsorption process follows the non-linear isotherm and the desorption process follows the linear isotherm. The breakthrough time of ACF filters was examined in the concentration range of 60 ppb to 13 ppm. The relationship of breakthrough times at different concentration levels was established and the breakthrough time of ACF filters at lower concentrations can be extrapolated from the results obtained at higher concentrations. Competitive adsorption of indoor VOCs shortens the breakthrough time of ACF filters and reduces their adsorption capacities on each individual VOC. The Ideal Adsorbed Solution Theory effectiveness was examined for predicting adsorption capacity of each chemical in a binary mixture, and the prediction was found to agree quite well with experimental results.
Zimmerman, Purdue University.
Occupational safety|Public health
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