Rapid nanosheets and nanowires formation by thermal oxidation of iron in water vapour and their applications as Cr(VI) adsorbent

Thermal oxidation of iron foil was done at 400 degrees C and 500 degrees C in for 2 h to form multilayered oxide scale with outer oxide layer of alpha-Fe2O3 comprising of nanowires and nanosheets respectively. Iron oxidized at 300 degrees C formed a rather compact film with no noticeable nanostructures. The morphologies of oxide formed in different oxidation environment (water vapour or dry air) were compared; densely packed nanostructures were produced in water vapour compared to dry air. Time variation study indicated rapid growth of nanostructure whereby for 1 min at 500 degrees C dense nanowires with some noticeable nanosheets were already observed. The nanowires and nanosheets were used to adsorb Cr(VI) from aqueous solution. Adsorption of 10 ppm of Cr(VI) on the nanowires and nanosheets was found to be successful with much faster removal efficiency for the nanosheets. Both samples displayed complete adsorption for less than 1 h. (C) 2016 Elsevier B.V. All rights reserved.