Oxidative recycling of metals is crucial for a circular economy, encompassing the preservation of natural resources, the reduction of energy consumption, and the mitigation of environmental impacts and greenhouse gas emissions associated with traditional mining and processing. Low-melting gallium trichloride appears to be a promising oxidative solvent for rare-earth metals, transuranium elements, platinum, pnictogens, and chalcogens. Typically, oxidative dissolution with GaCl₃ occurs at relatively low temperatures over a few days, assuming the presence of tetrahedral Ga–Cl entities. While supercritical gallium trichloride holds the potential for advanced recycling, little is known about its structure and viscosity. Using high-energy X-ray diffraction and multiscale modeling, which includes first-principles simulations, we have revealed a dual molecular nature of supercritical gallium trichloride, consisting of tetrahedral dimers and flat trigonal monomers. The molecular geometry can be precisely tuned by adjusting the temperature and pressure, optimizing the recycling process for specific metals. The derived viscosity, consistent with the reported results in the vicinity of melting, decreases by a factor of 100 above the critical temperature, enabling fast molecular diffusion, and efficient recycling kinetics.

中文翻译：

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氧化金属回收中的超临界三氯化镓：Ga2Cl6 二聚体与 GaCl3 单体及流变行为

金属的氧化回收对于循环经济至关重要，包括保护自然资源、减少能源消耗以及减轻与传统采矿和加工相关的环境影响和温室气体排放。低熔点三氯化镓似乎是稀土金属、超铀元素、铂、氮族元素和硫属元素的有前途的氧化溶剂。通常，假设存在四面体 Ga-Cl 实体，GaCl ₃的氧化溶解会在相对较低的温度下发生几天。虽然超临界三氯化镓具有先进回收的潜力，但对其结构和粘度知之甚少。利用高能 X 射线衍射和多尺度建模（包括第一原理模拟），我们揭示了超临界三氯化镓的双分子性质，由四面体二聚体和平面三角单体组成。通过调节温度和压力，可以精确调节分子几何形状，优化特定金属的回收过程。得出的粘度与熔融附近的报告结果一致，在临界温度以上降低了 100 倍，从而实现了快速的分子扩散和高效的回收动力学。