Rayon-based activated carbon fibers treated with both alkali metal salt and Lewis acid

Rayon precursors marinated by mixture aqueous solution containing NaCl and H3PO4 are activated by steam for manufacture of activated carbon fibers (ACF) in this work. It is interesting to find that mesopores (2 nm < pore size < 50 nm) and even macropores (pore size > 50 nm) are greatly developed on ACF surface, which indicates that NaCl + H3PO4 aqueous solution is an effectual pore size-enlarging impregnant. The influences of the concentrations of NaCl and H3PO4 on the pore distribution and morphology of the resulting ACFs are respectively examined by scanning electron microscopy (SEM), revealing that the pore structure can be controlled through an appropriate ratio of NaCl and H3PO4 impregnation. As it has been demonstrated that the adsorptivity of the ACF is related to the fractal characteristics of the pore structure, the fractal structure of the meso/macropores in the ACF is analyzed by the small angle X-ray scattering (SAXS) method, providing the characteristics of volume, size distribution and fractal dimension (D) of the pores, Finally BET analysis has confirmed that ACFs with abundant mesopores/macropores indeed exhibit highly effective adsorption capacity.