Surface properties of activated carbon fibers obtained from polyacrylonitrile and methyl acrylate: Experimental and simulation studies for lead and acid blue 25 dye adsorption from water

Activated carbon fibers were prepared using a methyl acrylate/polyacrylonitrile (MA/PAN) system and H3PO4 3 PO 4 activation. These fibers were assessed to adsorb AB25 and Pb2+ 2+ from aqueous solutions, and DFT calculations were carried out to determine the main surface interactions that caused the removal of both pollutants. The results showed that AB25 and Pb2+ 2+ adsorption on these activated carbon fibers was endothermic, with maximum experimental adsorption capacities of 0.012- 0.023 and 0.248- 0.306 mmol/g at 20 - 40 degrees C. Pb2+ 2+ adsorption properties of these fibers outperformed those of other carbonaceous materials utilized in the depollution of metallic cations, whereas their removal effectiveness was less competitive to separate AB25 dye molecules. A double-site monolayer model was applied to correlate the experimental Pb2+ 2+ isotherms, while AB25 adsorption on activated carbon fibers was simulated using a one-site multilayer model. Oxygenated acidic (i.e., carboxylic and phenolic) and phosphate-carbon functional groups were the main binding sites to adsorb these pollutants. The adsorption energies of the tested systems, the identification of the most feasible binding positions of the tested adsorbates on the activated carbon fiber surface, and the role of hydrogen bonding in the corresponding adsorption mechanisms were discussed using DFT calculations. These results contribute to the valorization and application of engineered materials such as activated carbon fibers for water depollution.