Influence of surface treatment on nickel (II) ion adsorption of stacked-cup type carbon nanofibers.

Influence of surface oxygen functional group (SOFG) of stacked-cup carbon nanofibers (CNFs) as adsorbents for nickel (Il) ion was investigated. The SOFG was introduced onto the original CNFs surface by treating the fiber with concentrated nitric acid solution for 3 hours. Adsorption study was carried out using nickel aqueous solutions of from 100 to 900 mg/L concentrations and contact time range from 60 to 180 minutes. The presence of SOFG was studied by FTIR spectroscopy. Field emission scanning electron microscopy was then used to characterize the morphology of the CNFs. Langmuir and Freundlich adsorption isotherm models showed that the acid modification which increases the number of oxygen functional groups on the fiber surface improves the nickel ion adsorption capacity.