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

点击翻译按钮获取中文摘要

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.