Mechanism-Guided Molten Salt Engineering via First-Principles Molecular Dynamics for Efficient Titanium Extraction...

Efficient chlorination of low-grade titanium slag demands a molten salt capable of withstanding the sustained enrichment of Mg/Ca chloride impurities without compromising transport properties. NaCl is widely regarded as an ideal molten salt medium. However, the atomic-level role of NaCl in modulating the Mg/Ca-Cl ionic network and governing Cl- mobility and melt viscosity remains unclear, thereby critically limiting the rational design of melt compositions for optimized titanium extraction. Here, first-principles molecular dynamics simulations were employed to reveal the structure-transport relationship in NaCl-MgCl2-CaCl2 molten salts with varying NaCl contents. Increasing NaCl content facilitated the dissociation of highly coordinated Mg- and Ca-centered clusters, weakened the connectivity of extended ionic networks, and increased the fraction of free Cl- ions. These structural changes promoted ionic mobility, resulting in enhanced diffusion and reduced shear viscosity. Considering shear viscosity, salt consumption, and density, an optimal composition window of 65-70 mol % NaCl was proposed. Chlorination experiments under the optimized molten salt conditions exhibited stable operation and achieved a high titanium extraction efficiency of 97.5%, validating the simulation-guided composition design. These findings reveal the atomic-scale mechanism governing structure-transport coupling in multicomponent chloride melts and provide a rational basis for molten salt design in low-grade titanium slag chlorination.