Synchrotron X-ray absorption spectroscopic study of thorium in ilmenite and titanium slag: towards green mineral processing

钍作为一种常见的放射性核素存在于一些矿石矿物、矿山废料和矿山尾矿中，一方面对环境构成严重威胁，但也是近年来日益可行的钍燃料循环中这种战略物资的潜在来源。因此，从矿石或废料中提取副产品钍不仅具有环境效益，而且具有经济价值。钍含量升高的三种材料是：(1)从独居石和氟碳铁矿矿石中提取稀土元素所产生的富含硬石膏和石膏的尾矿；(2)从焦绿石精矿冶炼以生产铌铁合金的焦绿石精矿所产生的铌铁渣；以及(3)从重矿砂中提取的钛铁矿精矿冶炼所产生的钛渣(用于生产二氧化钛颜料)。作为副产品的钍的提取和用于钍燃料循环的从矿山废物中回收钍都需要详细了解钍在宿主材料中的分布、形态和吸收机制。本研究与魁北克省Sorel-Tracy的Rio Tinto Fer et Tiane合作，旨在使用几种最先进的分析技术(例如微束同步X射线荧光图谱、同步X射线吸收光谱和电子顺磁共振光谱)来研究选定的钛渣和钛精矿中钍的分布、形态和吸收机制，应用于将对环境的辐射风险降至最低，并可能开发新技术来提取用于钍燃料循环的这种材料。该项目的具体目标包括：1)系统研究钍在钛渣和钛精矿中的分布；2)详细结构研究钛渣和钛精矿中钍的形态和吸收机理；3)从钛渣和钛精矿中提取钍的初步实验。这一基础研究和应用研究相结合的项目为萨斯喀彻温大学的一名博士生(Kamil Chadirji-Martinez)和一名本科生研究助理提供了极好的培训机会。

Thorium as a common radionuclide in some ore minerals, mine wastes and mine tailings poses a serious risk to the environment on the one hand but represents a potential source of this strategic material for the thorium fuel cycle that is becoming increasingly viable in recent years. Therefore, extraction of thorium as a byproduct from ores or waste materials not only has environmental benefits but also is of economic value. Three types of materials that contain elevated thorium contents are: (1) anhydrite- and gypsum-rich tailings stemming from the extraction of rare earth elements from monazite and bastnaesite ores; (2) ferroniobium slag from smelting of pyrochlore concentrates to produce ferroniobium alloy and (3) titanium slag (used for TiO2 pigment) from smelting of ilmenite concentrates extracted from heavy mineral sands. Extraction of thorium as a byproduct and recovery of thorium from mine wastes for the thorium fuel cycle both require detailed knowledge about the distribution, speciation and uptake mechanisms of thorium in host materials. The present study, in collaboration with Rio Tinto Fer et Titane of Sorel-Tracy, Quebec, is designed to use several state-of-the-art analytical techniques (e.g., microbeam synchrotron X-ray fluorescence mapping, synchrotron X-ray absorption spectroscopy, and electron paramagnetic resonance spectroscopy) to investigate the distribution, speciation and uptake mechanisms of thorium in selected titanium slags and ilmenite concentrates, with applications to both minimizing radiation risks to the environment and potential development of new techniques to extract this material for the thorium fuel cycle. The specific objectives of the proposed project include: 1) systematic study on the distribution of thorium in titanium slags and ilmenite concentrates, 2) detailed structural study on the speciation and uptake mechanisms of thorium in titanium slags and ilmenite concentrates, and 3) preliminary experiments to extract thorium from titanium slags and ilmenite concentrates. This project of combined basic and applied research provides an excellent training opportunity for one PhD student (Kamil Chadirji-Martinez) and one undergraduate research assistant at the University of Saskatchewan.