Preparation and evaluation of nitrogen-tailored hierarchical meso-/micro-porous activated carbon for CO adsorption.

In this study, nitrogen-tailored hierarchical meso-/micro-porous activated carbons were successfully fabricated from cypress sawdust by HPO activation with further nitrogen modification using three kinds of nitrogen source (i.e. nitic acid, urea and melamine). The produced carbons were used as adsorbents for CO capture. The physic-chemical properties of the produced carbons were characterized by N adsorption-desorption, fourier-transform infrared spectroscopy, scanning electron microscopy and X-ray photoelectron spectroscopy. The effects of pore structure and nitrogen content on CO adsorption were investigated. It was found that HPO activation would turn cypress sawdust into mesoporous carbon (AC), nitrogen doping could induce the development of microporosity and also increase the basicity of the carbon framework, which favoured for CO adsorption. Among the nitrogen-tailed carbons, HNO-treated activated carbon (AC-N) showed the highest (0.127 cm/g), the largest CO adsorption capacity (2.8 mmol/g at 273 K, 1 bar) and the best CO/N selectivity as compared to urea and melamine treated ones. The adsorption experiments showed that the presence of microporosity and pyrrolic-N on the carbons were responsible for CO adsorption, the oxygen functional groups on AC-N might also contribute to higher CO uptake, and the mesoporous structure could favour for the fast mass transfer of CO. The results of CO adsorption heat confirmed the high affinity of the prepared carbons to CO. This study provides a strategy to produce hierarchical meso-/micro-porous activated carbons with enriched nitrogen functional groups, which favoured for CO adsorption.