Purification processing has a great effect on carbon nanotubes.On one hand it can remove impurities and increase the surface area of carbon nanotubes.On the other hand it can introduce functional groups such as hydroxyl,carboxyl and carbonyl on the surface of carbon nanotubes.Both improved the adsorption capability of carbon nanotubes.The adsorption processes can be well modeled by isothermic equation Freundlich and equation de Boer-Ziwkker.The results also showed that carbon nanotubes can be regenerated and have great potential applications in environmental protection.
The adsorption of aniline on the as-grown and purified carbon nanotubes has been investigated. The initial concentration of aniline solution, time, temperature and pH values of aniline solution have great influence on the adsorption capacity. The adsorption capacity of the as-grown carbon nanotubes towards aniline was 4.8 mg/g at pH=5. For that treated with nitric acid, it increased to 15.4 mg/g. The adsorption capacity decreased with increase of temperature in the range of 283 to 303 K. The adsorption isotherms can be described by Freundlich equation.