Preparation of α-Fe2O3 hollow spheres, nanotubes, nanoplates and nanorings as high efficient Cr(VI) adsorbents

Abstract

α-Fe2O3 nanoparticle with different morphologies, such as hollow spheres, nanotubes with limited {0001} plane exposed, nanoplates and nanorings with the {0001} plane predominantly exposed, have been synthesised by using NaH2PO4 and urea in a facile hydrothermal method. The mechanism of the morphology evolution from hollow sphere to nanoring has been investigated. It is proposed that the polymerisation of Fe3+/H2PO4− plays an important role in the formation of these morphologies. The adsorption of Cr (VI) from aqueous solution onto these α-Fe2O3 nanoparticles showed that the α-Fe2O3 with nanoring morphology has the highest removal efficiency, and the adsorption capacity reached to 16.9 mg/g. These results indicate that the adsorption mechanism of Cr (VI) onto hematite nanoparticles is a chemisorption process through doubly and triply coordinated hydroxyl groups on the outer surface of α-Fe2O3.