Adsorption of Nitrogen Dioxide on Nitrogen-Enriched Activated Carbons

The aim of this study was to obtain nitrogen-enriched activated carbons from orthocoking coal. The initial material was subjected to a demineralisation process. The demineralised precursor was pyrolysed at 500 °C and then activated with sodium hydroxide at 800 °C. Activated carbon adsorbents were subjected to the process of ammoxidation using a mixture of ammonia and air at two different temperature variants (300 and 350 °C). Nitrogen introduction was carried out on stages of demineralised precursor, pyrolysis product, and oxidising activator. The elemental composition, acid-base properties, and textural parameters of the obtained carbon adsorbents were determined. The activated carbons were investigated for their ability to remove nitrogen dioxide. The results demonstrated that the ammoxidation process incorporates new nitrogen-based functional groups into the activated carbon structure. Simultaneously, the ammoxidation process modified the acid-base characteristics of the surface and negatively affected the textural parameters of the resulting adsorbents. Furthermore, the study showed that all of the obtained carbon adsorbents exhibited a distinct microporous texture. Adsorption tests were carried out against NO₂ and showed that the carbon adsorbents obtained were highly effective in removing this gaseous pollutant. The best sorption capacity towards NO₂ was 23.5 mg/g under dry conditions and 75.0 mg/g under wet conditions.