Adsorption of chromium (VI) on functionalized and non-functionalized carbon nanotubes by Mubarak, Nabisab Mujawar, Thines, Raj Kogiladas, Sajuni, Noor Rosyidah, Abdullah, Ezzat Chan, Sahu, Jaya Narayan, Ganesan, Poobalan, Jayakumar, Natesan Subramanian