Reaction-Mediator-Based Chlorination for the Recycling of Titanium Metal Scrap Utilizing Chloride Waste

Abstract

In this study, a novel chlorination technique for metallic titanium (Ti) was devised in order to establish a recycling process that uses both Ti metal scrap and iron chloride (FeCl_x) waste, and its feasibility was demonstrated. Direct reaction between Ti and FeCl_x has drawbacks such as slow kinetics of Ti chlorination and high volatilization of FeCl_x. To overcome these, the authors proposed a chlorination technique utilizing a reaction mediator in molten salt. Based on thermodynamic analyses of lanthanoid chlorides, some fundamental experiments were carried out with samarium trichloride (SmCl₃) as a reaction mediator. It was experimentally demonstrated that SmCl₃ in molten magnesium chloride (MgCl₂) can smoothly chlorinate Ti metal into gaseous titanium tetrachloride (TiCl₄), and the by-product SmCl₂ in the molten salt can be regenerated into SmCl₃ by FeCl₂. Thus, SmCl₃ in a molten salt works efficiently as a reaction mediator, and the newly proposed chlorination technique has the potential to make the Ti recycling process more efficient and environmentally friendly.