Geochemical and Mineralogical Significance of Trace Metals in Benue Trough Coal, Nigeria

In the present study, sub-bituminous coals from Ribadu, Okaba, Okpara, Orukpa, Ogboyoga and Lignite from Asagba, all from Benue Trough, Nigeria were analyzed by energy dispersive x-ray fluorescence spectrophotometer (EDXRF). Different concentrations of trace metals present in the coal samples were recorded and subsequently used to determine the origin, organic matter input, maturity and mineralogical importance of the coals. There is closeness between Chromium (Cr) and Nickel (Ni) content as well as V/Ni ratio for the coals suggesting that the organic matter is derived from terrestrial/marine and are of low maturity. Also, the low V/V+Ni ratios for all the coals suggest that they are deposited under oxic condition, which is in agreement with earlier work done on these coals by other workers. Therefore, these ratios compliment with other geochemical parameters can be a useful tool in geochemical studies. Preliminary assessments of the mineral contents of the coal samples reveal that there is possible occurrence of iron bearing minerals like pyrite, siderite and ankerite and titanium rich minerals; ilmenite and rutile in the studied area. This is due to high abundance of iron (Fe) and titanium (Ti) in the samples. Also the level of some metals such as nickel, iron, titanium and copper in these samples indicate that the ash residue of these coals after burning could be a very good source of the metals. However, the presence of some trace elements like copper (Cu) and nickel (Ni) that causes corrosion of the turbines and also poison catalyst, in the coals, necessitate incorporation of the removal procedures of these metals before refining stage.