Nano-XRF Analysis for Metal Speciation in Ash

Analysis of nano-XRF elemental maps can provide important insights about which elements often occur colocalized on a sub-particle scale, thus helping to suggest possible chemical forms present in the fly ash. Analyzing large amounts of nano-XRF data comes with several challenges, such as collinearity of elemental concentrations and particles with mixed phases. Within this project several different statistical approaches for analysis of nano-XRF data were identified and evaluated. The overall aim is to explain which elements are often colocalized with transition elements such as Zn, an element important both from environmental leaching and extraction viewpoint, in fly ash particles.

The methods evaluated include pixel selection based on correlation trends, cluster analysis, and factor analysis. The evaluated methods have their pros and cons, whereof some could explain parts of the elemental behavior of Zn in the fly ash particles. But none could handle the full complexity of the ash data. We therefore suggest alternative options to be explored in future analysis efforts.