Recovery and Purification of Titanium Dioxide and Aluminium Compounds from Corundum By-product of the TiPro Process

Abstract

The TiPro process developed at the University of Waikato utilises an aluminothermic reaction to create titanium rich intermetallic alloys or alloy powders by solid-liquid separation. The product is then reduced with calcium vapour or calcium hydride to lower the oxygen content. This process involves intimately mixing titanium oxide powder with stoichiometric quantities of aluminium powder and heating the mixture to initiate a thermite reaction that transfers oxygen from the titanium oxide to the aluminium to produce titanium aluminide alloy and aluminium oxide. The liquid alloy is drained off from the by-product, called corundum, before going on to further processing. The corundum is left behind and contains significant quantities of valuable titanium alloy and aluminium and titanium oxides which must be recovered to increase the efficiency and lower the cost of the process. This thesis describes and explains proof-of-concept wet chemistry methods of processing the corundum by-product to recover and separate the valuable metal oxides. Using acid-base equilibria, over 90% of the titanium was recovered from the corundum phase as impure titanium oxide. Aluminium was recovered as aluminium hydroxide and aluminium oxide, both of which can be processed into feedstock for fresh aluminium smelting and hence represent a potential revenue stream. The products were characterised using SEM-EDX and XRD to determine their composition and structure. The proposed treatment produces no waste other than environmentally benign neutral salt water.