Development of lignin-derived hierarchically porous carbon by one-step pyrolysis in an air/N₂ flow for efficient adsorption of organic pollutants

Hierarchically porous carbon (HPC) has shown to be advantageous over microporous carbon when applied as adsorbent of pollutants, but its preparation often involves sophisticated procedures. In this work, a lignin-derived HPC was produced simply by one-step pyrolysis in a mixed air/N-2 gas flow. The influence of treatment temperature and air ratio in gas flow on the porosity of HPC was investigated, and its hierarchical porosity was validated by analyses of pore size distribution, scanning electron microscope (SEM) and transmission electron microscope (TEM). The outperformance of HPC as adsorbent of organic pollutants was manifested by comparison with microporous carbon. Results showed that the most developed mesoporosity of HPC (mesopore surface area = 257 m(2)center dot g(-1)) was obtained at 700 degree celsius and an air ratio of 30% (by volume) in gas flow. The adsorption experiment showed that the mesopores of HPC dominated adsorption to two antibiotic pollutants (sulfamethazine and ciprofloxacin) of relatively large molecular size, while micropores of HPC also contributed to adsorption of 4-chlorophenol, a smaller molecular organic. The developed mesoporosity of HPC was also favorable for fast adsorption rate according to the adsorption kinetics study. Overall, this research provides a novel and green method for development of efficient carbon adsorbent by a simple pyrolysis process.