Backdrop & Context
China is home to the world’s most abundant titaniumresources, estimated at around 10 billion metric tons. These reserves aremostly embedded within vanadium-titanium magnetite ores, predominantly locatedin the Panzhihua region of Sichuan Province. During the ironmaking process,titanium is not extracted as a primary product but ends up in blast furnaceslag in the form of TiO₂,usually ranging between 10%–25%.
Despite its potential, this slag has historically gone underutilizeddue to the complexity of separating titanium from its host minerals.Traditional beneficiation methods, including flotation and magnetic separation,are inefficient due to the fine dispersion of titanium-bearing phases.Consequently, millions of metric tons of titanium-rich slag accumulate in openlandfills, causing severe environmental concerns while wasting valuableresources.
Who’s Involved?
At the forefront of addressing this issue is a researchteam comprising Jiqing Han, Li Zhang, Hongmei Yin, Qiuping Feng, and HongshengZhang. Working collaboratively across advanced materials science labs, theypublished their landmark findings in Scientific Reports, volume 15,article number 13961 (2025). Their work builds on a foundational technologydeveloped by Zhang Li and colleagues, who proposed using steel slag as anadditive to aid perovskite settling in molten slag.
Their interdisciplinary approach combined crystallography,metallurgical engineering, and thermodynamics to explore how precise quantitiesof steel slag could induce changes in the geometry of perovskite crystals, akey to optimizing titanium extraction.
Crystal Shapes, Steel Slag & GrowthKinetics
The research uncovered that perovskite crystal morphologyis directly influenced by the proportion of steel slag added to the system. Byconducting isothermal precipitation experiments, the team found that at 15%steel slag content, the perovskite crystals exhibited one-dimensional growth,forming dendritic or branch-like structures. At 25% and 35% slag, the crystalsadopted three-dimensional spherical forms.
This transformation is crucial. According to Dr. Li Zhang,“Spherical crystals are significantly denser and exhibit higher terminalvelocities when settling in molten slag. This allows for more effectiveseparation of titanium-bearing phases from impurities.”
The researchers quantified the growth kinetics using theAvrami equation. The growth index "n" values of ~1.5, 2.5, and 2.5for 15%, 25%, and 35% slag respectively confirmed the change from linear tovolumetric growth. This provides a predictive model for industrial application.
Mechanism Behind the Metamorphosis
Steel slag contains various oxides, including CaO, SiO₂, MgO, and Fe₂O₃, which influence thethermodynamic stability of perovskite phases. When added in controlled amounts,these components alter the local environment in molten slag, affectingnucleation energy barriers and encouraging isotropic crystal growth.
Dr. Qiuping Feng explains, “Steel slag acts as amicrostructural modifier. It reduces surface energy anisotropy, leading touniform spherical growth. This understanding allows us to fine-tune crystalmorphology during slag treatment.”
The transition from dendritic to spherical forms is morethan cosmetic; it fundamentally changes how crystals behave under gravitationalforces in high-temperature environments. Efficient settling paves the way foreasier physical extraction, reducing the need for chemical separation steps.
Industrial Implications & EnvironmentalRelief
This development represents a paradigm shift in theprocessing of titanium-bearing blast furnace slag. Currently, more than 60million metric tons of such slag are produced annually in China, most of whichare unused and stored in environmentally hazardous slag heaps.
With this new understanding, industries can integrate steelslag adjustments directly into their smelting lines. This minimizes energyconsumption by avoiding additional beneficiation steps, drastically reducesslag storage needs, and recovers a previously inaccessible titanium resource.
Dr. Hongmei Yin notes, “We are transforming waste intowealth. This method has the potential to recover an additional 1.5 millionmetric tons of titanium per year in China alone, which could feed domesticindustries and reduce import dependency.”
From Lab to Furnace: What’s Next?
While laboratory experiments have confirmed the theory, thenext phase involves scaling this up to pilot furnaces. Engineers will testdifferent slag formulations under real-world operating conditions to determinethe most efficient and cost-effective slag recipe.
Dr. Jiqing Han emphasizes, “Industrial translation is thekey. We are in talks with major steel producers to initiate pilot testing. Theend goal is to create automated control systems that dynamically adjust slagcontent to optimize perovskite settling in real-time.”
Researchers are also exploring the possibility of using AIand machine learning to monitor crystallization patterns through in-furnaceimaging systems, thereby enhancing process control and reproducibility.
Scientific Value & Global Impact
This study is not just relevant to China. Countries likeIndia, South Africa, and Russia, which also produce titanium-bearing slag,could benefit immensely from this approach. The technique also aligns withglobal sustainability goals by promoting circular economy principles in heavyindustries.
Dr. Hongsheng Zhang concludes, “Our work bridges the gapbetween fundamental science and practical metallurgy. By mastering the kineticsand thermodynamics of crystal growth, we can revolutionize how criticalminerals like titanium are recovered—responsibly, economically, andefficiently.”
Key Takeaways:
