Evidence of the dominant role of particle size in controlling the dynamic adsorption breakthrough behavior of gaseous benzene in a microporous carbon bed system

Abstract

To learn more about the competing roles of the key process variables (e.g., particle size vs. space velocity) in the adsorption of volatile organic compounds (VOCs), the breakthrough (BT) behavior of gaseous benzene (at 3 Pa) was investigated using microporous activated carbon (AC) beds built individually with each of four different particle size ranges (<0.6, 0.6–1.7, 1.7–2.36, and 2.36–5 mm) at three flow rates (300, 500, and 1000 mL min−1). The effects of each variable on AC performance were evaluated in relation to the occurrence patterns of BT. The key performance metrics (e.g., capacity and partition coefficient) generally increased with decreases in particle size and flow rate, reflecting the critical role of sorbent bed physical properties (e.g., surface area, space velocity, and residence time) in the adsorption process. The smallest particle group (<0.6 mm) exhibited the highest uptake rate in the initial BT stage in terms of breakthrough volume (BTV: L g−1) (e.g., BTV5% (5% BTV) = 424 L g−1). In contrast, the order for 100% BT was reversed to record the highest at the largest particle group (2.36 – 5 mm). The kinetic modeling suggests the dominant role of the pore-diffusion mechanism on the overall adsorption process with enhanced benzene uptake rate onto smaller carbon particle sizes at higher flow rates. Based on this work, we recommend accurate determination of the relative dominance between adsorbent particle size and space velocity to maximize the efficiency of air filtration systems for real-world applications.