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Chemical Leaching of an Indian Bituminous Coal and Characterization of the Products by Spectroscopic Techniques

B. Manoj

Fourier transform infrared (FTIR) spectra of high volatile bituminous coal as well as their insoluble organic matter, obtained by chemical leaching with HF, EDTA and acid mixture (HF + HCl and HF + HNO3) were recorded between 500 and 4000 cm-1. UV-Visible-NIR spectroscopy was used to study the sample and its leached products in the 200-800 nm wavelength region. Oxygen containing structures were observed in the 1800-1000 cm-1 zone, aliphatic hydrogen in the 2920-2800 cm-1 zone, aromatic outof-plane structure in the 900-670 cm-1 zone. A great abundance of C=C structure was noticed at 1600 cm-1 region, while clay and silicate minerals were identified in the 540 cm-1 and 1030 cm-1 region. With chemical leaching silicate bands showed a decrease in intensity and were least for EDTA and HF leached samples. The UV-Visible -NIR spectrum showed absorption maximum at 235-270 nm and was shown a red shift with leaching. The П-П* electronic transitions of the poly-nuclear aromatic hydrocarbons was responsible for the absorption at 680 nm. The weak bands observed in the visible region (400-500 nm) were due to the presence of SO2 in the sample and decreased with chemical leaching. It was evident from the results that amongst the leachants used, hydrofluoric acid and acid mixture had significant effect in removing the mineral matter and oxygenated functional groups.