Formaldehyde removal by Rayon-based activated carbon fibers modified by P-aminobenzoic acid

We impregnated Rayon-based activated carbon fibers (ACFs) by p-aminobenzoic acid (PABA) and systematically investigated their porous structure, surface chemistry, and formaldehyde removal behavior. Using standard nitrogen adsorption analysis, we found that the specific surface area, the micropore volume, and the total pore volume decreased with increasing concentration of PABA. Through elemental analysis and X-ray photoelectron spectroscopy, it was found that some nitrogen-containing functional groups presented on the surface of modified Rayon ACFs. The modified Rayon-based ACFs showed much higher adsorption capacity and longer breakthrough time for formaldehyde than did as-prepared Rayon-based ACF. We proposed that the improvement of formaldehyde removal by modified ACFs was attributed to the combined effects of physisorption contributed by pore structures and chemisorption contributed by the N-containing functional groups, whereas there was only physisorption between the as-prepared ACF and formaldehyde molecules.