Recovery of titanium from low-grade titanium alloy grinding scrap: Staged regulation of the conversion of Ti, TixOy to TiO2

Abstract

Titanium alloy grinding scrap (TAGS) is a low-grade scrap produced by grinding during titanium alloy processing. Due to the high impurity content and complex phase composition, TAGS currently has no effective resource utilization pathway. In this study, a new method based on ball milling pretreatment, cascade electrostatic separation, oxidative roasting, and acid leaching was proposed to achieve deep separation and purification of Ti from low-grade TAGS. The results show that the resistivity between the titanium-containing phase and the impurity in TAGS varied greatly, and the resistivity of titanium metal was significantly lower than that of Ti_xO_y and TiO₂. The stripping of the high-resistivity oxide layer from the surface layer of titanium metal was achieved by ball milling under an N₂ atmosphere, which significantly enhanced the effect of cascade electrostatic separation. It was beneficial to increase the roasting temperature and time to promote the conversion of Ti and Ti_xO_y to TiO₂. TiO₂ with a rutile structure did not dissolve during the HCl leaching process. Except for corundum (Al₂O₃), most of the impurities (Fe₂O₃, MgAl₂O₄, etc.) would react with HCl and enter the solution as ions. Under the optimized conditions (ball milling time = 30 min, voltage = 21 kV, cascade electrostatic separation 3 times, roasting temperature = 950 °C, roasting time = 3 h), the Ti grade was increased from 18.36 wt% to 54.86 wt% with a TiO₂ content of 91.44 wt%. The Ca and Mg content (CaO + MgO) in the products was <1.25 wt%, which met the requirement of titanium-rich material and realized the high-value utilization of low-grade TAGS.