Abstract
Low-cost walnut shell-based carbons with high microporosity were prepared by simple one-step carbonization with chemical activation using KOH, exhibiting the promising potential to be a very good CO 2 and H 2 adsorbent. The physicochemical properties of the obtained carbons were characterized by N 2 and CO 2 adsorption isotherms, X-ray powder diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), and elemental analysis. The activated carbon AC-800 was characterized by a highly developed specific surface area of 1868 cm 2 /g and a high micropore content of 0.94 cm 3 /g. It highly exhibited CO 2 uptake in 1 bar was up to 9.54, 5.17, 4.33 mmol/g for 0, 25 and 40 °C, respectively. In addition, the H 2 storage capacity was 3.15 mmol/g at 40 bars. Significantly, confirmed an exceptionally high dependency of CO 2 and H 2 uptake vs micropores structure of activated carbon. AC-800 also shows good selectivity for CO 2 /N 2 and fast adsorption kinetics that be easily regenerated with superior cyclic stability after multiple cycles The experimental isotherm data of activated carbon produced from walnut shells were analyzed using Langmuir, Freundlich, Temkin, Sips, and Toth isotherm equations. The fitting details showed that the multitemperature Toth equation is a powerful tool to mathematically represent CO 2 and H 2 isotherms on activated carbon. The easy way of preparation and high capture abilities endow this kind of activated carbon attractive as a promising adsorbent for CO 2 and H 2 storage. • Walnut shells have been used successfully to synthesize AC. • AC display an appropriate micropore structure to achieve high H 2 and CO 2 adsorption capacity. • The mechanism of CO 2 and H 2 adsorption has been explained. • AC-800 had high CO 2 /N 2 adsorption selectivity and stability. • Sample AC-800 display great potential for low-temperature H 2 storage.
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