A Review of Application of Synchrotron-Based X-Ray Techniques in Sulfide Mineral (Bio)leaching

Abstract

Synchrotron-based technologies can provide an incomparable and unique characterization capacity over laboratory-based techniques to improve our understanding of complex mineral processing. In the last 20 years, synchrotron-based technologies, including XAS, SXPS, SXRD, PEEM, SPEM, STXM, and XCT, have been widely used in the characterization of (bio)leaching of metal sulfides in different aspects. These technologies provided an in-depth understanding of mineral-solution reaction mechanisms in mineralogy, electronic properties of sulfide minerals, surface chemistry, solution chemistry, leaching intermediate species, as well as biochemistry of bacteria and bacteria-mineral interactions. In particular, XAS and SXPS have been used to understand the properties of minerals and their stepwise dissolution by cross-evidence from spectra of S, Cu, Fe, As, etc. These studies revealed the dissolution mechanisms of a variety of metal sulfides with economic and environmental importance such pyrite, chalcopyrite, pyrrhotite, arsenopyrite, enargite. In-situ XAS and XRD have provided a unique approach to quantitatively understand the leaching mechanisms and processes in real-time. Spatially resolved technologies such as PEEM, SPEM, and STXM further elucidated the mechanisms of heterogeneous oxidation of these minerals, and microbe-mineral interaction. In addition, Synchrotron CT shows an incomparable advantage in obtaining quantitative 3D mineralogy and tomographic data, which advanced our understanding in particle void development and metal sulfide dissolution. Important directions for the use of synchrotron in sulfide (bio)leaching include using in-situ characterization to monitor the leaching process that may not be fully reflected by sampling and integrating advanced endstations and AI algorithms to better distinguish leaching intermediate and products.