Inorganic constituents lignite

In lignites the inorganic constituents are incorporated not only as discrete mineral phases, but also as relatively mobile ions, presumably associated with the carboxylic acid functional groups. The distribution of inorganic constituents has been studied principally by the chemical fractionation procedure developed by Miller and Given (13). 

Geochemical Variation of Inorganic Constituents in a North Dakota Lignite... 

A Montana lignite (Fort Union Seam) was utilized in this study. The major inorganic constituents present in this lignite can be classified as discrete mineral phases and ion-exchangeable cations. 

The raw lignite was demineralized in order to study the effect of mineral matter on the properties of the final product. Removal of the inorganic constituents of the raw coal was accomplished by acid washing of the initial material with HCl and HF acid solutions [45]. About 120 ml of 5N HCl were added to 18 g of coal in a glass beaker. The mixture was stirred for one hour at room temperature. The treated coal was then filtered and washed with distilled water. Subsequently, the coal was mixed with 120 ml of full strength (22N) HF in a plastic beaker. This mixture was also stirred for one hour at 25 2°C, then filtered off and washed. The coal residue was then mixed with 120 ml of full strength (12N) HCl for a third treatment, for one hour at the same temperature. Finally, the coal was filtered, washed, and dried at 373K in an inert atmosphere. 

---