Enhanced bamboo charcoal-based adsorbent for dichloromethane adsorption within a wide relative humidity: Adsorption performance, moisture resistance and mechanism analysis.

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.