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TRACE ELEMENTS IN SULPHIDE AND SULPHATE MINERALS IN COAL AND THEIR ENVIRONMENTAL IMPACT

I. Kostova

Abstract

The trace elements in the main sulphide and sulphate minerals in coal were determined. Coals with different degree of coalification (ranging from lignite to subbituminous) from three important Bulgarian coal basins – Maritza East, Pernik and Balkan have been investigated. Heavy liquids and hand picking under a binocular stereomicroscope were applied to concentrate the sulphur-bearing minerals present in coal. Trace elements in them were detected by inductively coupled plasma – atomic emission spectroscopy (ICP – AES) of separated fractions. Some elements determinations were also carried out with scanning (SEM) and transmission (TEM) electron microscopes equipped with energy dispersive X-ray analyzers. Determination of sulphide and sulphate minerals in coal samples were performed using optical microscopy, X-ray diffraction and SEM (micromorphometric particle analysis). Pyrite, marcasite and gypsum are the major sulphur-bearing minerals in studied coals. The trace elements presented in pyrite are Mo, Co, Ni, Cu, As, Zn, V, Cr, Mn, Al, Pb, Ge, Sb, Ga, Si, Cd, Ca, Y, Ti, Ba, K and Bi. The elements As, Mo, Zn, Co, Mn, Ni, Cd, Cr, Si, V, Ga and Sr have been detected in marcasite. In gypsum were determinate the following trace elements : Sr, Mo, Mn, Fe, Yb, Cr, V, Ga, Al, Ti, Y, Ni and K. Some genetic and environmental conclusions related with interdependence between the elements and the main sulphur-bearing minerals have been done.

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