Activated carbon based selective purification of medical grade NO starting from arc discharge method

Four activated carbons were tested under normal temperature and pressure to selectively adsorb nitrogen dioxide (NO2) from medical nitric oxide (NO) formed by arc discharge. The samples’ pore structures were characterized by an automatic specific surface area and porosity analyzer based on the Brunauer–Emmett–Teller method, t-plot, and the Barrett–Joyner–Halenda method. Surface chemical properties both before and after adsorption, as well as the resultant nitro-compound (C-NO2 or nitrate) after adsorption, were analyzed using the classic Boehm titration method and Fourier transform infrared spectroscopy. The selective adsorption amounts of NO2 and NO were evaluated using specially designed equations. It was found that, with their large surface areas and highly acidic groups, spherical activated carbon from wood and activated carbon fibers had the best selective adsorption of NO2. It was also shown that the large difference in acid–basic surface groups and the molecular polarity between NO and NO2 accounted for their adsorption on different functional groups, and that those acidic groups enhanced the selective adsorption of NO2. The research on regeneration and re-adsorption showed that regeneration had an obvious effect on the adsorption of NO2, but little effect on NO.