Characterization of gas phase adsorption capacity of untreated and chemically treated activated carbon cloths

Granular activated carbon (GAC) and powdered activated carbon (PAC) have long been used to effectively treat drinking water, waste water, and industrial gas streams. Undesired contaminants are removed by adsorption onto activated carbon. While activated carbon has been used extensively in industrial applications, little research has been performed to evaluate using activated carbon to remove low concentrations of volatile organic compounds (VOCs) from indoor air environments. In this research, activated carbon cloth (ACC) is examined for its equilibrium adsorption capacity for several VOCs of relevance to indoor air quality.;Adsorption isotherms were measured for acetaldehyde, acetone, benzene, methyl-ethyl ketone, and water vapor and three ACC types in the 10 to 1000 ppmv concentration range. Water vapor adsorption was not significant on ACC until relative humidities above about 50% (P/P;ACC-20 was chemically modified, producing oxidized, chlorinated, and nitrated samples. Adsorption capacities for VOCs in the 10 to 1000 ppmv concentration and water vapor from 0 to 95% RH were measured. Oxidized ACC-20 showed an enhanced physical adsorption for acetaldehyde, acetone, and water vapor, probably due to increased dipole-dipole interactions and hydrogen bonding. Oxidation of ACC-20 changed the shape of the water vapor adsorption isotherm, so that it no longer resembles a Brunauer type V. Benzene showed a decreased adsorption capacity on oxidized ACC-20, which may be due to an increase in hydrophilicity of ACC-20 or a change in pore size distribution.;Chlorination had little effect on VOC adsorption capacity, except in the case of acetone, where a decrease in adsorption capacity occurred. Nitridation of ACC showed little effect on organic adsorption capacity, but increased the saturation adsorption capacity for water vapor on ACC-20 and increased the breadth of its hysteresis loop. These changes were the result of changes in the pore size distribution of the nitrided ACC-20.;The effects of relative humidity (RH) on the adsorption of soluble (acetone) and insoluble (benzene) volatile organic compounds (VOCs) on activated carbon cloths (ACC) were measured. A gravimetric balance was used in conjunction with a gas chromatograph/mass spectrophotometer to determine the individual amounts of water and VOC adsorbed on an ACC sample. RH values from 0 to 90% and organic concentrations from 350 to 1000 ppmv were examined. The presence of water vapor in the gas-stream along with acetone (350 and 500 ppmv) had little effect on the adsorption capacity of acetone even at 90% RH. Water vapor in the gas-stream had little effect on the adsorption capacity of benzene (500 ppmv) until about 65% RH, when a rapid decrease in the adsorption capacity of benzene resulted with increasing RH. Increasing benzene concentration, however, can significantly decrease the amount of water vapor adsorbed.