A regenerable N-rich hierarchical porous carbon synthesized from waste biomass for HS removal at room temperature.

In this study, N-rich hierarchical porous carbons (NPCs) were synthesized via one step strategy from cypress sawdust with carbon nitride (CN) loading and KCO activation. NPCs exhibited excellent performance for HS removal with the sulfur capacity up to 426.2 mg/g at room temperature. It was much higher than 12.5 mg/g of porous carbon (PC) which was only activated by KCO. The NPCs with CN loading showed hierarchical porous structure with micropores and mesopores volume up to 0.434 and 0.597 cm/g, respectively. Moreover, NPCs had high N contents (up to 12.37 wt%) and high relative contents of pyridinic N and pyrrolic N within 76.61-84.37%, which were identified as active sites for HS adsorption by density functional theory calculation, enhancing HS removal. The formation mechanism of NPCs was investigated by TG-FTIR, suggesting that CN pyrolysis result in hierarchical porous structure and rich N-containing functional groups by gradually releasing HO, CO and NH. Moreover, the NPCs showed high regeneration ability, remaining 86.6% of the initial sulfur capacity after five regeneration cycles, and sulfur (S) was the main desulfurization product (HS + O → S + HO). The results demonstrate that NPCs are promising catalysts to remove HS efficiently with low cost and high reusability.