Modification of the adsorption model for the mixture of odor compounds and VOCs on activated Carbon: Insights from pore size distribution

Abstract

The coexistence of volatile organic compounds (VOCs) and odor compounds is a prevalent feature in various industrial exhaust gases. However, a precise mathematical model for the co-adsorption of these pollutants on activated carbon is currently lacking. This study introduces a correction factor to enhance the Langmuir model and investigates its relationship with the pore size distribution of activated carbon through experimental methods. The adsorption behaviors of carbon disulfide (CS2) and toluene on 14 activated carbon samples were thoroughly examined. The findings indicate that micropores smaller than 0.71 nm predominantly influence CS2 adsorption, while micropores smaller than 2 nm significantly impact toluene adsorption. Accordingly, the Langmuir competitive adsorption model can be refined by introducing the ratio of competitive adsorption pore volume to individual adsorption pore volume. The resulting corrected predictive model demonstrates a significantly improved correlation with experimental results. The modified model's applicability was extended to universal multicomponent adsorption systems. Furthermore, the study reveals that the replacement ratio of CS2 adsorption capacity by high-concentration toluene is approximately 24.8, and the roll-up proportion of CS2 from activated carbon can be estimated by dividing the adsorption capacity of toluene by 521 mg/g. This investigation not only elucidates competitive adsorption patterns in gas and solid phases but also unveils mechanisms within micropores, providing valuable insights into the competitive adsorption process between CS2 and toluene. These insights are crucial for optimizing fixed bed adsorbers used in odor compounds and VOCs emission control.