Yttrium partitioning and associations in coal-combustion ashes prior to and after their leaching in HCl

Yttrium associations and partitioning within fluidised-bed coal combustion ashes were studied in particle-size fractions prior to and after their leaching in cold dilute HCl. In original ash fractions (not leached in HCl), the dominant association of Y to P2O5 and TiO2 was revealed while after the leaching, the strength of relationship to P2O5 decreased considerably and TiO2 exhibited the only significant correlation. Overall HCl-extraction percentage of Y from these ashes was ca. 50% with TiO2-associated Y predominantly contributing to insoluble fraction. Yttrium percentage dissolved in HCl can be attributed to its affinity to soluble phosphates (e.g., fluor/hydroxy apatites) or its potential occurrence in the form of Y2O3 or YCl3.