Effect of fabrication conditions on the porous structure of polyacrylonitrile-derived carbons and their influence on dye adsorption and gas separation

The adsorption technique for pollutant separation has increased the number of applications, and one of the most interesting aspects is focused on the fabrication of new tailored materials. This research is focused on producing carbons as adsorbent materials from polyacrylonitrile (PAN), aiming to promote the presence of such heteroatoms as nitrogen and sulfur, already embedded in the precursor and added during fabrication, respectively. The use of various fabrication conditions (temperature, amount of activating agent, KOH and/or sulfur, S) has allowed the production of carbons with different pores distributions (microporous and mesoporous materials) and containing heteroatoms. In general, it was observed that both an increase in temperature and a higher amount of KOH or S tend to increase the size of the pores generated in the carbons. These materials have been used for CO2 separation and for the removal of industrial red dye, demonstrating the significant role of the carbon's porous structure in the adsorption process. On the one hand, for CO2 separation, the microporous materials showed outstanding behavior, achieving suitable loading and selectivity values. The red dye adsorption studies proved the existence of a size exclusion effect that hinders pollutant removal, as highly microporous carbons hardly could remove the contaminants. In contrast, this separation was enhanced by slightly increasing the average pore size (values above 2 nm).