Enhanced bamboo charcoal-based adsorbent for dichloromethane adsorption within a wide relative humidity: Adsorption...

Dichloromethane (DCM) is widely used in industry and is one of the key components of industrial exhaust. The paramount challenge for bamboo charcoal (BC) as a common adsorbent is how to achieve high adsorption capacity at high humidity, especially for some chlorinated volatile organic compounds (Cl-VOCs). Herein, the adsorption capacity of BCNK2-800 (2:1:1 mass ratio of KOH, urea and BC, 800 °C pyrolysis), for DCM under dry conditions was 610.9 mg/g, which was the highest value reported in the literature. The adsorption ability still stayed at 87.6 % (535.2 mg/g) of that obtained under dry condition, even as the relative humidity increased to 80 %. The specific surface area of BCNK2-800 rose from 332.96 up to 1590.4 m²/g, and the water contact angle increased from 116.5° to 137.9°, indicating that BCNK2-800 had more adsorption sites and better hydrophobicity than BC800. Density functional theory calculations showed that N-containing groups reduced the preferential occupation of adsorption sites by water vapor. The desorption and regeneration of saturated BCNK2-800 was carried out with 5 % ethanol at 80 °C, and the adsorption capacity was still > 90 % after 5 cycles. Compared to conventional high-temperature regeneration method, this approach could be easier to implement and more energy-efficient. Competitive adsorption studies indicate that BCNK2-800 prefers to adsorb VOCs with higher hydrophobicity. Such a modified bamboo charcoal-based adsorbent performed better adsorption ability for VOCs over a wide range of humidity, which provided a feasible solution for the treatment of actual industrial waste gases.