Sequential Leaching of Trace Elements in Coal: a Case Study from Talcher Coalfield, Orissa

The extent of vaporisation and subsequent condensation of many trace elements during coal combustion is largely dependent upon the mode of occurrence of the trace elements, besides many other parameters. Mode of occurrence of a few important trace elements in coals from Talcher coalfield representing low and high ash type from Karharbari and Barakar Formations is studied by sequential leaching experiments. It is observed that in both the coal samples, Cr and Mn exhibit more affinity towards organic matrix and/or insoluble oxide phases. Pb and Cd are mostly associated with soluble sulphide and oxide minerals. Co is mostly bonded with silicate phases in the coal samples. No definite mode of occurrence is visualised for Ni from the present study, as it is associated more with the residue indicating its association with either organic matrix or insoluble oxide.