An efficient tool for the continuous monitoring on adsorption of sub-ppm level gaseous benzene using an automated analytical system based on thermal desorption-gas chromatography/mass spectrometry approach

Abstract

It became an important task to effectively adsorb volatile organic compounds (VOCs) at or near real-world levels for efficient control of airborne pollution in ambient environments. Nonetheless, most studies carried out previously for the control of VOCs are confined to significantly polluted conditions (e.g., >100 ppm) that are far different from real-world or ambient conditions. To help acquire the meaningful data for the adsorptive removal of VOCs at near real-world levels, a new approach was designed and implemented to measure adsorption of gaseous benzene (as a representative or model VOC) at trace-level quantities (as low as 0.14 ng (0.43 ppb) for a 100 mL sample) using activated carbon (sieved to 212 μm mesh size) as a model sorbent. With the aid of a thermal desorption-gas chromatography/mass spectrometry system, the key adsorption performance metrics (such as 10% breakthrough volume (10% BTV) points: 10% as the key reference) were determined: 1018 L atm g−1 at 0.1 ppm benzene with the corresponding partition coefficient of 3.85 mol kg−1 Pa−1. If the adsorption capacity values (at 10% BTV) are compared across the varying concentration levels of benzene, the maximum value of 1.07 mg g−1 was observed at 1 ppm benzene (within the concentration range selected in this work). As such, it was possible to quantitatively assess the sorbate-sorbent interactions at significantly low concentrations of VOCs that actually prevail under the near real-world conditions.