Effect of two types of adsorption sites of activated carbon fibers on nitrate ion adsorption.

In this study, the activation with ZnCl and heat treatment at 950 °C were performed to polyacrylonitrile-based carbon fiber and phenol resin to prepare two types of activated carbon fibers (ACFs) with different amounts of quaternary nitrogen (N-Q). In order to investigate the effect of chemical properties of ACFs on nitrate adsorption, various experiments and assess were conducted on these samples. The pH of Py-7.0Z4-9.5HT10 and PhR-6.0Z4-9.5HT30 was about 7.1 and 7.0, respectively, and was no significant difference in the results. The C-π sites had a large effect on the amount of nitrate adsorption, and its adsorption capacity was greatest when the solution pH was about 3. However, the adsorption affinity (K) of C-π sites was weaker than that of N-Q, and the contribution for adsorption was small when the solution was low concentration or neutral, while the N-Q was the dominant adsorption site of ACFs. It is expected that the N-Q affected the adsorption kinetics, and the higher the amount of N-Q, the faster the adsorption rate. Py-7.0Z4-9.5HT10 had a large amount of C-π sites and N-Q. Therefore, the equilibrium adsorption amount (Q) of Py-7.0Z4-9.5HT10 was 1.02 mmol/g at solution pH 3, and the adsorption kinetics were also fast.