Role of Infrared Spectroscopy in Coal Analysis—An Investigation

Fourier transform infrared (FT-IR) spectroscopy is a widely used analytical technique for determining the different functional groups of a coal structure. This method, being able to reveal carbo-hydrogenated structures (aromatic and aliphatic) and heteroatomic functions (mainly oxygenated), as well as to detect the presence of minerals, is currently one of the most powerful techniques for coal characterization and thus is of paramount importance in the various utilization procedures of coal (industrial combustion, coke production processes, etc.). FT-IR study shows the presence of aliphatic -CH, -CH2 and -CH3 groups, aliphatic C-O-C stretching associated with -OH and -NH stretching vibrations and HCC rocking. It is conjectured that, the two-stage leaching using HNO3 followed by HF remarkably reduced the ash content as well as the minerals including Al, Si and Ca. The solubilization of samples with buffered EDTA could not eliminate the minerals in coal. The silicate and kaolinite bands showed a systematic lowering on EDTA and carboxylic acid treatment. The fungal leaching was most beneficial for aromatic molecules with different degrees of substitution. The intensity of bands due to carbonyl groups was increased, when treated with fungi, whereas that due to oxygen functional groups showed a reverse trend. The mineral bands due to silicates also decreased in intensity, on post treatment with fungal culture.