Physicochemical Characterization of Selected Ethiopian Stone-Coal

Abstract

Stone-coal is a nonrenewable heat energy source. It is drived from organic sedimentary rock, consisting of valuable organic materials and inorganic mineral impurities. These imputies are formed through the chemical and physical degradation of plant debris that becomes buried underground. The physicochemical characteristics of coal samples collected from different mining areas were investigated in this study using conventional and spectroscopic methods. Fourier Transform Infrared Spectrometry (FTIR), X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Gravimetric and Volumetric analysis, and Atomic Absorption Spectrophotometer (AAS) techniques were employed to examine the carbon functional groups, structural crystallinity, surface morphology, and concentrations of different heavy metal oxides and trace metals, respectively. Different aromatic, aliphatic and bridge chains functional groups were observed in the examined samples from FTIR spectra. The Value of XRD indicates the change in coalification stage interrelating with crystallinity and aromaticity. The SEM images results % porosity and average particle sizes in range of 14.45 – 17.48 % and 155.74 – 203.16 nm. The results obtained from AAS showed that the concentrations of heavy metals in mg/g ranged from 3.62 ± 0.14 to 12.60 ± 1.02 (for copper), 4.57 ± 0.37 to 103.40 ± 3.83 (for zinc), 4.71 ± 0.27 to 99.23 ± 1.76(for lead), 32.41 ± 0.86 to 160.34 ± 0.94 (for nickel) and 131.80 ± 2.5 to 223.76 ± 2.99 (fo cobalt). The results of proximate and ultimate analysis showed that the moisture contents ranged from 0.53 ± 0.05, to 4.27 ± 0.08%, volatile matter ranged from 21.32 ± 0.41 to 36.57 ± 0.42%, ash content raged from 28.60 ± 0.01 to 39.70 ± 0.47%, fixed carbon raged from 30.55 ± 0.46 to 38.45 ± 0.11%, and sulfur contents raged from 0.78 ± 0.06 to 1.41 ± 0.05%. The calorific values ranged from 4087.67 ± 8.50 to 4672.33 ± 20.50 cal/g. The concentration of metal oxides obtained from coal ash analyzed by volumetric titration and gravimetric analysis ranged from 10.38 ± 0.37 to 14.92 ± 0.62% (for iron oxide), 28.14 ± 0.59 to 33.70 ± 0.82% (for aluminum oxide), 1.46 ± 0.10 to 10.94 ± 0.34% (for calcium oxide), and 35.39 ± 0.30 to 43.77 ± 0.17% (for silicon dioxide). In general, the analytical results were statistically approved by single factor ANOVA and the physicochemical characteristics of each selected sample were thoroughly investigated to establish a baseline for the different uses and environmental concerns of the selected coal areas.