MMIJ Annual Meeting

Coal is a complex mixture of organic matter and mineral phases, both of which can host toxic and trace elements. Understanding their mode of occurrence is essential for assessing environmental risks associated with coal mining and utilization. This study investigates the mineralogical composition and trace element distribution in the Mbinga bituminous coal deposit, located in the Ngaka coalfield of the Ruhuhu Basin in Tanzania. Optical microscopy and field-emission electron probe microanalysis (FE-EPMA) were used to characterize mineral phases and their chemical compositions.The dominant minerals identified include pyrite, barite, rutile, zircon, and rare earth element (REE)-bearing phosphates. Trace elements that were observed in minerals include: nickel (Ni), copper (Cu), scandium (Sc), platinum (Pt), aluminum (Al), chromium (Cr), calcium (Ca), and hafnium (Hf); and REE-phosphates, which are enriched in cerium (Ce), lanthanum (La), neodymium (Nd), and yttrium (Y), with significant thorium (Th) and praseodymium (Pr). These results highlight the diverse modes of trace element occurrence in coal, which has implications for environmental pollution during coal combustion, handling, and waste disposal. The presence of pyrite also suggests a risk of acid mine drainage. Understanding these mineralogical and chemical relationships provides a foundation for designing appropriate mitigation strategies, such as pre-combustion coal cleaning and post-combustion gas treatment technologies.