Characterization of Coals and Coal Ashes with High Si Content Using Combined Second-Derivative Infrared Spectroscopy and Raman Spectroscopy

Abstract

The organic and mineral components in two coals and resulting high-temperature ashes with high silicon content were characterized by second-derivative infrared spectroscopy, Raman spectroscopy, and X-ray diffraction (XRD). The infrared spectra of raw coals show weak organic functional groups bands but strong kaolinite bands because of the relatively high silicates content. In contrast, the Raman spectra of raw coals show strong disordered carbon bands but no mineral bands since Raman spectroscopy is highly sensitive to carbonaceous phases. The overlapping bands of mineral components (e.g., calcite, feldspar, and muscovite) were successfully resolved by the method of second-derivative infrared spectroscopy. The results of infrared spectra indicate the presence of metakaolinite in coal ashes, suggesting the thermal transformation of kaolinite during ashing. Intense quartz bands were shown in both infrared and Raman spectra of coal ashes. In addition, Raman spectra of coal ashes show a very strong characteristic band of anatase (149 cm–1), although the titanium oxides content is very low. Combined use of second-derivative infrared spectroscopy and Raman spectroscopy provides valuable insight into the analyses of mineralogical composition. The XRD results generally agree with those of FTIR and Raman spectroscopic analyses.

Raman Spectroscopy of Crystals

“…Raman spectra of raw coals showed intense carbon peaks but no mineral matter peaks. The XRD analyses of mineral composition of coals and coal ashes generally agreed with the results of infrared and Raman spectra [7].…”

Potential Usage of Hybrid Polymers Binders Based on Fly Ash with the Addition of PVA with Satisfying Mechanical and Radiological Properties

“…This band overlapped with a broad characteristic band centered at 1045 cm −1 . This peak is attributed to the Si-O stretching in tetrahedrons characterized by silicon bound to three bridging oxygen units and one non-bridging oxygen [ 44 , 45 ]; Si–O–Si symmetric or Al–O–Si asymmetric stretching mode. These structures are the building blocks of geopolymers [ 46 , 47 ].…”

“…The Si–O bending bands are found at 880 cm −1 . The peaks at 790 cm −1 and 468 cm −1 corresponded to quartz’s symmetric Si–O stretching vibrations [ 45 ]. According to the literature [ 50 , 51 ], vibration bands attributed to secondary building units made of joined SiO 4 and AlO 4 tetrahedral, forming variously membered rings in the 800–550 cm −1 region.…”

Novel Fibrous Silica-Copper Sulfide Nanocomposite (KCC1-CuS): Synthesis and Enhanced Photocatalytic Degradation of Humic Acid

“…Also these peaks have been appeared in FTIR spectrum of KCC-1/CuS nanocomposite. The Si-O bending, Si-O symmetric and asymmetric stretching vibrations were indicated by the peaks at 465, 1102, and 796 cm -1 , respectively (Yin et al 2019). The presence of O-H molecules may also be demonstrated by the appearance of 3420 cm -1 FTIR peak (Fihri et al 2012, Huang et al 2014).…”