Converting lignocellulosic biomass into mesoporous carbons for the assessment of single adsorption equilibrium: the competing role of moisture and temperature on gaseous benzene adsorption

Abstract

For the present study, the activated carbon were obtained from Lotus corniculatus L. as waste biomass using carbonization at 700 °C and alkali potassium hydroxide (KOH) chemical activation technique. Single gaseous benzene (C₆H₆) adsorption (SGBA) experiments were performed to benchmark the efficiency of the L. corniculatus-derived activated carbons (LCACs), which were LCAC2 (609 m² g⁻¹, KOH 1:2 w/w), LCAC3 (742 m² g⁻¹, KOH 1:3 w/w), and LCAC4 (826 m² g⁻¹, KOH 1:4 w/w), respectively. Also, the physicochemical properties of LCACs were characterized by Fourier Transform Infrared Spectroscopy (FT-IR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and proximate-elemental assessment. The isotherm models (Langmuir and Freundlich) of C₆H₆ demonstrate the complex adaptation results of LCAC4 at different relative humidity (RH) levels, and Freundlich isotherm is highly suitable to C₆H₆/LCAC4 as multilayer adsorption. Kinetic behavior was also analyzed and showed that of C₆H₆ is well illustrated by the pseudo second order (PSOM). The C₆H₆ competitive adsorption of LCAC2, LCAC3, and LCAC4 at 25 °C + 0 RH%, 25 °C + 80 RH%, 45 °C + 0 RH%, and 45 °C + 80 RH% corresponds to reductions of 12.9–11.6%, 7.8–11.5%, and 9.9–18.4%. The LCAC4 is confirmed to be a perfect adsorbent in the elimination of a single gaseous stream at 45 °C + 0 RH%. Regeneration showed that the LCAC4 maintained more than 25% of the initial adsorption capacity after five repeated adsorption–desorption cycles. The promising properties of LCAC4 are recommended to be exploited for the other volatile organic compounds in the gas phase in indoor environments, under the best conditions.