Effect of modification with HNO3 and NaOH on metal adsorption by pitch-based activated carbon fibers

Pitch-based activated carbon fibers (ACFs) were modified with nitric acid a nd sodium hydroxide. Their physicochemical properties were investigated in terms of N-2 adsorption, mass titration, FTIR and metal adsorption. The spe cific surface area of the ACFs decreased after oxidation with 1 M nitric ac id, but the total acidity increased three times compared to the untreated A CFs, resulting in an improved ion-exchange capacity of the ACFs. The points of zero charge of the ACFs that affect the selectivity for the ionic speci es changed from pH 6 to pH 4 by 1 M nitric acid and to pH 10 by 1 M sodium hydroxide treatment. Upon oxidation of the ACFs with nitric acid, surface o xide groups were observed in the FTIR spectra by absorption peaks at 1750-1 400 cm(-1). The carboxyl groups of ACFs decreased, while the lactone groups increased after the sodium hydroxide treatment. The adsorption capacity of copper and nickel ion is mainly influenced by the lactone groups on the ca rbon surface pH<pH(zpc), and by the total acidic groups at pH>pH(zpc). (C) 2001 Published by Elsevier Science Ltd.