Geochemistry, mineralogy and speciation of heavy metals in wastes of coal washing plant of Alborz-e- Shargi Company (Semnan province)

This study aims to investigate the content, geochemical speciation and mobility of heavy metals as well as mineralogical characteristics of wastes in a coal washing plant (Alborz-e-Sharghi Company). The obtained results revealed that coal wastes as compared to world coal mean are normal to enriched in terms of Pb, Cu, Ni, Cr and As while are depleted with respect to Cd and Zn. XRD analysis indicated that quartz, kaolinite, illite, calcite, calcite, siderite, gypsum and pyrite are present in the studied samples. The results obtained from speciation analysis showed that Pb, As, Cu, Ni and Cr were mainly associated with phases 6 and 5 (sulfide and silicate bound fractions) while Zn and Cd were mostly retrieved from phase 1 (water soluble fraction). The mobility factors also confirms that Zn and Cd with 53.32 and 44.12 % are the most mobilizable elements. This is particularly prominent for 30 years aged coal wastes. This study generally concludes that most mobilized metals such as Zn and Cd have the high potential to find their ways into the surrounding environments and this should be considered in future assessments and management of coal waste produced in the study area.