Geochemical investigation and modes of occurrence of critical elements and minerals in the coal of Akkakhel, Akhorwal, and Sheikhan, KP, Pakistan

Abstract

The present study probed the quantity of critical elements and minerals in Akkakhel, Akhorwal, and Sheikhan coal deposits located in Kohat, Pakistan. For this purpose, thirteen coalmines were sampled for the determination of critical elements and minerals in coal. The results showed that the critical elements in the coal namely, magnesium (Mg), calcium (Ca), potassium (K), iron (Fe), sodium (Na), silver (Ag), manganese (Mn), cobalt (Co), nickel (Ni), cadmium (Cd), chromium (Cr), copper (Cu), zinc (Zn), sulfur (S), and lead (Pb) were relatively higher than the world's coal and upper continental crust. The higher concentration of critical elements is attributed to the spinel group, sulfides, carbonates, and clay minerals. In all the coalfields, quartz and pyrite minerals' existence and mode of occurrence were common in Akkakhel, Akhorwal, and Sheikhan coalmines. The minerals namely, anatase, gibbsite, calcite, periclase, and palygorskite minerals were common in Akhorwal and Sheikhan coalmines. The critical elements were associated with montmorillonite, potassium sulfide, sillimanite, hematite, chalcopyrite, illite, goldichite, spinel, phengite, sphalerite, dolomite, ilmenite, and siderite minerals. Moreover, the identification of mineral phases through SEM and XRD analysis results in the reduction of sulfur to a considerable level through the froth flotation technique, which limits the SOx emission to the atmosphere. The data obtained during this study will be useful for the industries such as energy, power, space technology, and cement manufacturing. However, sustainable mining, extraction of minerals, and utilization of mining wastes will limit the negative impacts on the environment.