New insights into hierarchical pore size and level of concentration in efficient removal of toluene vapor by activated carbon

Abstract

The hierarchical pore structure of nanoporous carbon and gaseous toluene concentration co-mediated adsorption mechanism was examined. The KOH-activated carbons with tailorable high surface area (1126–3148 m2/g), large pore volume (0.446–2.08 cm3/g) and broadening average pore width (0.873–2.68 nm) were prepared. Dynamic adsorption was used to determine breakthrough curves and adsorption isotherms of toluene by as-prepared KOH-activated carbons and commercial activated carbons. The experimental results showed that the breakthrough time is positively correlated with ultramicropore volume of all activated carbons. The equilibrium amounts adsorbed (qe) for toluene at 100 ppmv were as high as 454 mg/g on KOH-activated carbons. The qe for toluene at P/P0 < 0.017 dominated by ultramicropore volume of all activated carbons were attributed to the enhanced superposition of adsorption force field between adjacent ultramicropore walls. A large adsorption affinity is imperative to achieve high amounts adsorbed for toluene at low concentration. The toluene was firstly filled in ultramicropores then gradually occupied in wide micropores at 0.017 <P/P0 < 0.1 and the qe were linearly correlated with micropore volume. The qe of toluene at P/P0 > 0.1 were linearly correlated with volume of micropore and small mesopore. The governing porosity in adsorbing toluene is varied with the intruding concentration. These results provided new insights into adsorption mechanism and development of novel materials.