Synthesis of multi-walled carbon nanotubes on ‘red mud’ catalysts

Red mud, a toxic waste product from bauxite processing, was used as a catalyst for the synthesis of multi-walled carbon nanotubes (MWCNTs) by fluidised bed chemical vapour deposition. The products were analysed using thermogravimetric analysis, Raman spectroscopy, and transmission electron microscopy. Using ethylene at 650 °C a MWCNT yield of 375% (with respect to Fe loading) was obtained. Carbon products were approximately 75% MWCNTs with an IG/ID ratio from Raman spectroscopy of 1.43. The production technique and reaction conditions used are conducive to large-scale CNT production, offering a potential value-added commercial use for red mud.