Hydrometallurgical recovery of mechanochemically synthesized Ti-Mg alloy powder from milled Tio2-Mg powder mixture

Abstract

Ti-Mg alloy has desirable mechanical and other properties but is difficult to form by conventional ingot metallurgy. This work reports the results of a hydrometallurgical investigation on the recovery of Ti-Mg alloy powder synthesized from mechanochemical processing (MCP) of TiO2 with Mg (15 wt.% beyond stoichiometric). The MCP synthesized alloy powder is intrinsically mixed with MgO and other oxides of Ti. The objective was thus to find a leachant that can leach out the by-products of the MCP process. Different inorganic and organic acid media, and their combinations, were used to try and recover a pure isolated Ti-Mg powder. For comparison purposes, the dissolution of individual particulate polycrystalline MgO and TiO2, and Ti-20Mg (obtained from milling blended elemental powders) was also investigated. The study indicated that separation with inorganic acids (HCl, H2SO4, and aqua regia) was not possible since as high as 80% of the milled Ti-Mg alloy powder was dissolving, yet the target TiO2 was still undissolved under the same conditions. Recovery of Ti-Mg powder was not achieved with organic acids as well because MgO and TiO2 showed marked resistance to dissolution and hence would contaminate the alloy powder. There was drastic co-dissolution of MCP TiO2-Mg in combined HCl/organic acids while the TiO2 resisted dissolution.