Multi-stage independent temperature controlled gradient crystallization method for molten salt purification

作者：Zhengjia Zhao, Yuke Zhong, Mincheng Yang, Lin Wang, Tao Zhang, Ziyu Liu, Yalan Liu, Wei‐Qun Shi · 发表于：Separation and Purification Technology · 年份：2025 · DOI：10.1016/j.seppur.2025.134546 · 被引用次数：4 · 研究领域：Molten salt chemistry and electrochemical processes、Crystallization and Solubility Studies、Bauxite Residue and Utilization

The accumulation of fission products in molten salt electrolysis significantly deteriorates salt performance and reduces process efficiency. Although conventional molten salt crystallization techniques exhibit attractive purification capabilities, their application is constrained by high equipment costs and operational complexity. Herein, we present a novel approach, termed “multi-stage gradient crystallization” (MSGC), based on natural temperature gradient crystallization, for the efficient removal of fission products from molten salts. Experiments on treating LiCl salts containing 5 wt% SrCl 2 demonstrated significant purification under a cooling rate of 5 ℃/2h, achieving SrCl 2 removal efficiencies of 80.1 % and 91.2 % at 80 % and 60 % salt recovery rates, respectively. Secondary crystallization further improved these efficiencies to 84.6 % and 98.3 %. The developed MSGC process not only maintains high purification efficiency but also significantly increases the single-batch treatment capacity. In addition, in-situ synchrotron radiation X-ray micro-computed tomography (SR-μCT) revealed the dynamic mechanism of LiCl’s top-down gradient crystallization and its gradual separation from SrCl 2 in the LiCl-SrCl 2 molten salt. This method exhibits excellent purification performance for various fission elements and molten salt systems, demonstrating broad applicability and promising potential for waste salt purification.