Adsorption performance of multi-walled carbon nanotube-SiO₂ adsorbent for toluene

In this study, multi-walled carbon nanotube (MWCNTs)-SiO₂ composite adsorbents MWCNTs-SiO₂-2, MWCNTs-SiO₂-4, MWCNTs-SiO₂-6 (CS2, CS4, CS6) with molar percentages of MWCNTs of 38%, 52%, and 66% were synthesized using the sol-gel method. The effects of the MWCNT content, temperature (30−60 °C), water vapor concentration (1%−5%), and the number of cycles on the adsorption capacity of toluene were studied, and an adsorption kinetics analysis was performed. The results showed that the adsorption capacity for toluene at 30−60 °C was AC (activated carbon) < CS2 < CS4 < CS6, and the adsorption capacity of CS6 to toluene was up to 50.28 mg/g. For every 10 °C increase in temperature, the penetration time decreased by 10−20 min, and the adsorption content decreased by 3.5% for every 1% increase in water vapor concentration. The phase with the fastest mass transfer rate of toluene could be described by the quasi-secondary adsorption kinetics model, in which intraparticle diffusion plays a major role. The mole percentage of MWCNTs ranged from 38% to 66%, the higher the content was, the easier it was to adsorb toluene. The functional group types of the MWCNTs-SiO₂ adsorbent after regeneration did not change, and the adsorbent maintained good adsorption performance.