Titanium (Ti) recycling has emerged as a vital industrial process due to the increasing global demand for this strategic metal, especially in aerospace, medical, and high-performance industrial applications. Titanium’s high cost and energy-intensive primary production, dominated by the Kroll process, make recycling a compelling alternative for reducing both environmental impacts and raw material dependence. The recycling process faces dual challenges: economically recovering high-purity titanium and overcoming contamination, particularly from oxygen. The current landscape of titanium recycling is characterized by scrap classification, metallurgical melting technologies, and ongoing efforts in chemical deoxidation to enable closed-loop high-quality Ti reuse.
The production of ferrotitanium (Fe-Ti) begins with the careful sorting and weighing of input materials to ensure they meet the target compositions required for the alloy. This is followed by the induction melting process, which is conducted under argon to prevent oxidation and nitrogen uptake. Once the melting process is complete, the molten material is cast into ingots, which are then mechanically broken down into specified sizes for further use. This method is particularly advantageous because it can use lower-grade titanium scrap, which is often unsuitable for high-purity applications. However, ferrotitanium production does not permit the complete recycling of materials into titanium metal and thus represents a form of downcycling.
High-purity titanium scrap is ideally suited for direct recycling into ingots through various vacuum-based remelting processes, which are essential due to titanium’s strong affinity for oxygen and nitrogen at elevated temperatures. One such process is Vacuum Arc Remelting (VAR), in which scrap is integrated into a consumable electrode and melted under vacuum. Additionally, both Plasma Arc Melting (PAM) and Electron Beam Melting (EBM) are used to melt titanium in a protective or high-vacuum environment, with EBM additionally purifying the melt by removing high-density inclusions such as tungsten carbide. Another emerging technology, Cold Crucible Induction Melting (CCIM), employs water-cooled copper crucibles segmented to allow eddy-current penetration, enabling controlled melting without contamination from refractories. The primary advantage of these advanced melting technologies is their capability to produce aerospace-grade titanium. However, their broader adoption is constrained by the equipment’s high costs and complexity, as well as the requirement for high-purity feedstock.
Various laboratory-scale deoxidation methods have been explored to mitigate oxygen contamination in titanium recycling. One approach is Solid-State Electrotransport, which can effectively reduce oxygen content; however, geometric constraints and the complexity of the required equipment limit its use. Another method is Calcium Deoxidation, where calcium reacts with oxygen to form calcium oxide (CaO). This technique is enhanced by employing molten-salt fluxes, which dissolve CaO, thereby reducing its activity and promoting further deoxidation.
Additionally, Rare-Earth Metal Deoxidation, particularly with yttrium (Y), has shown promising results due to its strong thermodynamic driving forces that facilitate oxygen removal. Hydride Deoxidation is another innovative strategy in which magnesium is combined with titanium hydride under hydrogen pressure, thereby reducing oxygen content in powder-based titanium from 0.35% to 0.16%.
Despite the theoretical effectiveness of these methods, none have yet achieved commercial scalability. As a result, the current practice in titanium recycling primarily relies on diluting oxygen-rich scrap with virgin sponge titanium.
In practice, titanium recycling involves a multi-step integration of mechanical, thermal, and chemical techniques. The industry distinguishes between closed-loop recycling, in which high-grade scrap is directly reused (e.g., aerospace machining swarf), and open-loop recycling, which involves remelting or alloying low-grade scrap for secondary applications such as ferrotitanium.
Titanium’s reactivity necessitates processing under vacuum or inert conditions at virtually every stage. While high-grade scrap is routinely reprocessed using VAR or EBM, lower-grade scrap lacks an economically viable purification method, limiting its reuse to alloying agents.
The development of commercial deoxidation technologies would be transformative, enabling the full reintegration of a wider range of Ti scrap into the titanium supply chain. Countries without primary sponge titanium production, such as South Korea, could significantly benefit from such innovations, enhancing self-sufficiency and reducing reliance on imports.
Titanium recycling is essential for the sustainable supply of this strategic metal, yet its industrial viability is constrained by technical limitations, most notably oxygen contamination. While advanced vacuum melting technologies ensure the production of high-purity ingots from selected scrap, the challenge of economically deoxidizing titanium remains unresolved at scale. As such, titanium recycling continues to rely on a tiered approach: remelting high-quality scrap, downcycling lower-grade scrap into alloys, and blending with virgin titanium to meet purity requirements. Ongoing research into deoxidation, especially involving calcium, rare-earth elements, and hydride methods, offers a pathway to a more circular and resilient titanium economy. Further industrial-scale validation and process optimization will be critical for realizing this potential.