Toluene adsorption studies on carbon-based materials under controlled temperature, humidity, flow rate, and toluene concentration, using a high-precision dynamic adsorption set-up

Volatile organic compounds (VOC) can have harmful effects on human health. Physisorption using carbon-based materials is one of the most commonly used methods for removing toxic VOC from indoor air. In this study, three carbon-based materials, including hydrophilic granular activated carbons (GAC1 and GAC2) and hydrophobic Carbotrap X (CX), were investigated for toluene adsorption using a novel dynamic set-up. The efficiency of toluene removal can vary depending on several experimental factors. Therefore, adsorption experiments were conducted under stable and precisely controlled conditions of temperature, humidity, flow rate, and pollutant concentration. Our findings show that adsorption temperature, high humidity, and the textural properties of the materials can influence toluene adsorption capacity. Additionally, pollutant concentration plays a role, as demonstrated by adsorption isotherm models such as Langmuir, Freundlich, Temkin, and Redlich-Peterson. The results indicate that GAC1, with its large specific surface area (SSA = 974 m²/g) and high micropore content (>80%), is a promising material for toluene physisorption in indoor air at a medium relative humidity (≤ 50% RH). Its adsorption capacity can reach up to 342 ± 41 mg/g under conditions of 14–20 mg adsorbent mass, 23 °C, 50% relative humidity, and 40–200 mL/min flow rate. Notably, hydrophobic CX shows potential as an effective VOC adsorbent material, particularly in extremely high-humidity environments.