Biomass derived hierarchical porous carbon for high-performance O 2 /N 2 adsorption; a new green self-activation approach.

Biomass-derived porous carbons are the most common adsorbent materials for O 2 /N 2 adsorption because of their excellent textural properties, high surface area, and low expense. A new synthesis method based on a self-activation technique was developed for a new green porous carbon adsorbent. This ecofriendly system was used for the synthesis of hierarchical porous carbons from walnut-shell precursors. The sorbent was successfully synthesized by facile one-step carbonization, with the activating reagents being gases released during the activation. The sample morphology and structure were characterized by field emission scanning electron microscopy, high-resolution transmission electron microscopy, Raman, Fourier transform infrared spectra, X-ray photoelectron spectroscopy, X-ray powder diffraction, thermogravimetric, and differential thermal analysis. The optimal porous carbons were synthesized at 1000 °C, providing a surface area as high as 2042.4 (m 2 g -1 ) and micropore volume of about 0.499 (m 3 g -1 ). At 298 °K under 9.5 bar pressure, the potential for O 2 /N 2 separation using porous carbon samples was studied, and the sips isotherms with the highest adsorption potential were determined to be 2.94 (mmol g -1 ) and 2.67 (mmol g -1 ), respectively. The sample exhibited stable O 2 /N 2 separation over ten cycles, showing high reusability for air separation. Finally, the technology described presents a promising strategy for producing eco-friendly porous carbon from a variety of biomass on an industrial scale.