Chemical Solubilization of Coal using HF and Characterization of Products by FTIR, FT Raman, SEM and Elemental Analysis

B. Manoj, A.G. Kunjomana

Department of Physics, Christ University, Bangalore, Karnataka, India 560029 Research and development Cell, Bharathiar University, Coimbatore, Tamil Nadu, India.

DOI: 10.4236/jmmce.2010.910067                

Abstract

An examination of the structural features of sub-bituminous coal samples from Godavari coal field, India were carried out by Scanning Electron Microscopy (SEM), FTIR, FT Raman, and elemental analysis. SEM micrograph analysis of virgin coal revealed the features of lithophiles like aluminium, silicates and calcium. To remove minerals and enhance the carbon content, the sample was leached with HF of different concentrations. FT Raman spectra in the range 100 to 3500 cm^-1 region were obtained for coal samples. The same sample was recorded with FTIR for comparison purpose. The spectrums were found to have similar broad characteristics. Certain bands were found to be both Raman and IR active. Variation in band intensity and position was found to be sample dependent. Graphite and defect band was observed on the Raman spectrum. The absence of the features corresponding to inorganic elements in HF leached residual samples was an indication of demineralization. The CHNS analysis showed that the oxygen content decreased by 63% when treated with HF (20%) where as carbon content increased by about 29.63%. The calorific value a remarkable increase of 37% with HF (10%) leaching. In the SEM micrograph of leached sample cracks and devolatization holes were observed. Proximate analysis showed a systematic decrease in ash content from 12.87 wt% to 3.06 wt% with leaching. It was evident from the results that Hydrofluoric acid had significant effect in removing the mineral matter and oxygenated functional groups from the coal.

Keywords

FT Raman; SEM; FTIR; chemical leaching; elemental analysis.

Conflicts of Interest

The authors declare no conflicts of interest.

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