Preparation Of Monolithic Activated Carbon Foam And Its Adsorption Characteristics For VOCs

Great attention has been paid to volatile organic compounds (VOCs) due to its environmental pollution and great harm to human health. Activated carbon adsorption is the most-commonly-used method due to its economical and effective removal of VOCs. Efficiency of the adsorption method depends mainly on the properties of activated carbon material, so development of new activated carbon materials is very important for VOCs control in environment protection.A new kind of material called monolithic activated carbon foam (MACFoam) was successfully prepared from mesophase pitch and coal by foaming process at high temperature and high pressure, being carbonized and activated by steam. Its BET specific surface area is about 700m2/g and compressive strength is about 0.5MPa. Its physicochemical properties and hydrodynamic performance were tested. Benzene, toluene, acetone and ethyl acetate were selected as the representatives of VOCs and their adsorptive behaviors on the MACFoam bed have been studied in comparison with that of TF-1 honeycomb activated carbon and MJ-09 granular activated carbon.The pores in this MACFoam are inter-connected with each other and their diameters are larger than 300μm, the airflow can easily pass through the MACFoam bed. In the same condition, pressure drop of MACFoam bed is approximately the same as that of 0.9mm diameter granular carbon bed.The BET area of this MACFoam is about 700m2/g and its mesopore volume is more than 0.2ml/g. It has high benzene adsorptive capacity and excellent desorption ability. Saturated adsorption capacity of MACFoam bed for Benzene almost remains the same after ten adsorption-desorption cycles. This material can be used as absorbent for air purification.The breakthrough curves of the MACFoam bed for the adsorption of single component (benzene, toluene or acetone) were studied at different concentrations and airflow rates. The results indicated that the Yoon-Nelson equation are applicable to predict the breakthrough behaviors of the single component on the MACFoam bed.In the case of binary components(benzene-toluene and acetone-ethyl acetate), the adsorptive ability of benzene or acetone is weaker than that of its competitor (toluene or ethyl acetate), the benzene and acetone breakthrough curves present as "humps". In the process of continuous adsorption, the pre-adsorbed benzene or acetone can be substituted by toluene or ethyl acetate gradually. At the top of the "hump", the benzene or acetone concentration was higher than its initial value.The Wheeler equation was used to calculate the breakthrough curves of benzene, acetone and ethyl acetate on the MACFoam, MJ-09 granular activated carbon and TF-1 honeycomb activated carbon beds respectively, the adsorptive abilities of MACFoam and MJ-09 granular activated carbon are obviously better than that of TF-1 honeycomb activated carbon.