Development and Evaluation of Carbonaceous Adsorbents from Agricultural Residues for Control of Volatile Organic Compounds

摘要

Four agriculture residues, including raw barley husk, bio-treated barley husk, rice husk, and pistachio shell, were used as starting materials to produce activated carbons with diverse physical and chemical properties. The adsorption behavior of volatile organic compounds for resulting adsorbents was tested with toluene as an adsorbate. Results showed that with adequate steam activation time (30?90 min, 50% H2O(g)), activated carbons with a surface area between 360 and 950 m2/g were developed. Further increases in the activation time destroyed the pore structure of activated carbons, which resulted in a decrease in the surface area and pore volume. Elemental analyses and X-ray photoelectron spectroscopy examination suggested that the oxygen content of activated carbons increased with increasing activation time. These results indicate that H2O molecules react with the carbon surface to form oxygen-containing acidic functional groups. Results from adsorption of toluene (inlet concentrations between 50 and 600 ppmv) at 40 to 80 °C showed that the adsorption capacities increased as the inlet toluene concentration increased, and decreased with increasing adsorption temperature. These data were successfully fitted with Freundlich and Dubinin-Radushkevich (DR) isotherms (R2 > 0.96). The obtained Freundlich constants and DR parameters can then be used to predict equilibrium adsorption capacities at various adsorption conditions.