Adsorption and oxidation of high concentration toluene with activated carbon fibers

Abstract

Many of the factors influencing the adsorption of volatile organic compounds by activated carbon fibers (ACFs) have been widely studied. However, most of them were investigated at low concentrations (500 ppm or less) and at low adsorption temperatures (lower than 100 °C). This study was to determine simultaneously the oxidation and adsorption of toluene onto activated carbon fibers (ACFs) at high concentration and high adsorption temperatures. We tested three ACFs, four inlet concentrations of toluene (700, 1,200, 1,600, and 2,000 ppm), and four adsorption temperatures (25, 50, 75, and 200 °C). The composition and morphology of the ACFs were also analyzed using BET, FTIR, EA, and FESEM. The results indicated that the best toluene adsorption capacity was for 569 mg/g ACFs at a toluene concentration of 1,200 ppm and at 25 °C. A combination of low O content and high mesopore volume was desirable for ACFs with a high toluene adsorption capacity at high toluene concentrations. Moreover, the breakthrough time decreased with increasing toluene concentration, and the adsorption capacity of toluene increased significantly when the inlet concentration of toluene increased to 1,200 ppm. The data also indicated that the breakthrough time and the adsorption capacity of toluene decreased with increasing adsorption temperature. The outlet concentration of toluene did not reach 1,200 ppm when adsorption was saturated at 200 °C, as the oxygen functional groups on the ACF surface had reacted with toluene to form other compounds.