Exploration of the compositional phase space of metallurgical slag models for a rational design of processes of refractory metal recovery through smelting and recrystallization

熔渣系统的多组分、复杂的性质提供了巨大的优势，因为熔炼和控制冷却后可以形成广泛的晶相组合。这些晶相可以通过选择性地从炉渣基质中分离出来进行回收。然而，同样的复杂性给合理的工艺设计带来了巨大的挑战，这些工艺保证(I)在晶体中装入足够的值得回收的基本元素，以及(Ii)在回收率(工艺速度)和周转率(工艺效率)方面的可行性。在这个项目中，我们将实施一种合理的方法来从冶金锡和铜渣中识别和表征富含难熔金属元素(特别是Ta、Nb、Mo)的工程人造矿物(ENAM)相。该方法基于对炉渣成分相空间的监督探索，以便在添加添加剂后筛选、识别和合成ENAM相，以促进所需相的结晶并阻止不想要的相的形成。我们的主要假设是，对炉渣成分相空间和ENAM形成机理的合理和公正的认识将使我们能够设计出通过冶炼和再结晶以高回收率和高效率进行元素回收的工艺。这一假说的工作将分三个步骤进行，即：(1)通过数据库搜索和密度泛函计算，从理论上快速筛选大量潜在的ENAM候选者，以回收一组目标元素，然后通过火焰喷雾热解合成选定的候选者；(2)设计和理解模型渣的激光诱导熔炼和再结晶过程，包括添加促进形成富含目标元素的大而可分离的ENAM晶体的添加剂；(3)将多种材料表征方法与理论全局最优化方法相结合，在原子尺度上精确识别ENAM相，实现晶体结构的无偏确定。我们希望我们的研究能够为从多组分体系中形成富含难熔元素的晶相的热力学和动力学提供深刻的知识，这些知识将被转移到现实世界的炉渣和工业规模的过程中。

The multicomponent, complex nature of slag systems offers great advantages with respect to a wide portfolio of crystal phases that can form after smelting and controlled cooling. These crystal phases can be recovered by selective separation from the slag matrix. However, the same complexity poses great challenges to a rational design of processes which guarantee (i) sufficient loading of the crystals with the essential elements that are worth being recovered and (ii) viability in terms of recovery rate (process speed) and turnover (process efficiency). In this project we will implement a rational methodology for the identification and characterization of Engineered Artificial Mineral (EnAM) phases rich in refractory metal elements (especially Ta, Nb, Mo) from metallurgical tin and copper slags. The methodology is based on the supervised exploration of the compositional phase space of the slags, in order to screen for, identify and synthesize EnAM phases after addition of additives to promote crystallization of desired phases and hinder the formation of unwanted ones. Our leading hypothesis is that the rational and unbiased knowledge of the slag compositional phase space and EnAM formation mechanisms will enable us to design processes for the elemental recovery through smelting and recrystallization with high recovery rates and efficiency. The work towards this hypothesis will be structured in three steps, namely: (1) the fast theoretical screening of a very large number of potential EnAM candidates for the recovery of a set of target elements via database searches and DFT calculations, followed by the synthesis of selected candidates via flame-spray pyrolysis; (2) the design and mechanistic understanding of a laser-induced smelting and recrystallization process for model slags, including the addition of additives promoting the formation of large and separable EnAM crystals rich in target elements; (3) the precise identification of the EnAM phases at the atomic scale combining several material characterization methods with a theoretical global-optimization method for the unbiased determination of crystal structures. We expect our study to provide profound knowledge of the thermodynamics and kinetics of the formation of crystal phases rich in refractory elements from multicomponent systems, which will be transferable to real-world slags and industrial-scale processes.