Enhanced adsorption of As(III) on chemically modified activated carbon fibers

Abstract In this study, potentials of Fe- and HNO3-modified activated carbon fiber (ACF) for the adsorption of As(III) from aqueous solutions were evaluated. The adsorbent was characterized by Brunauer–Emmett–Teller (BET), scanning electron microscopy and X-ray diffraction spectra. It was found that both the modified ACF and unmodified ACF had large specific surface areas. Compared with the unmodified ACF, the crystallinity of the Fe- and HNO3-modified ACF showed a trend of decrease. The final equilibrium was achieved within approximate 60 min, and the removal of As(III) was significantly influenced by the initial pH. Isotherm simulations revealed that the ACF exhibited effective adsorption capacity for As(III) in aqueous solution. The adsorption isothermal data fitted the Langmuir isotherm model better than the Freundlich isotherm model for the unmodified ACF and HNO3-modified ACF, but the Freundlich isotherm model was more suitable for the Fe-modified ACF. According to the Langmuir models, the maximum adsorption capacity of As(III) was 2.06, 2.98 and 8.65 mg/g for ACF-0, ACF-1 and ACF-2, respectively. The results demonstrated that the adsorption capacity was enhanced significantly by Fe and HNO3 modification, and the Fe-modified ACF showed a higher potential for the adsorption of As(III) ion from aqueous solution than the unmodified ACF and HNO3-modified ACF.