[Spectroscopy Characterization of Anthracite Oxide].

Understanding coal structure is essential for material science. Prior research has shown that coal metamorphism affects carbon properties. However, the exact structural changes during oxidation remain unclear. This gap motivated the need for detailed spectroscopic analysis. Coal types like bitumite and lignite have been studied extensively. But anthracite's intermediate structure has not been fully characterized. The role of oxidation in modifying anthracite is not well established. This paper's contribution lies in using XRD, Raman, and ATR-FTIR to explore structural transformations. The study aims to bridge the knowledge gap about anthracite's oxidation process.

The study aimed to characterize anthracite and its oxide using spectroscopic methods. The specific problem addressed is the lack of detailed structural data on oxidized anthracite. The motivation stems from anthracite's potential in activated carbon production. The researchers wanted to understand how oxidation alters anthracite's structure. They focused on structural properties like crystallite size and order. The study also examined functional groups introduced during oxidation. The goal was to determine if oxidation could enhance anthracite's utility. The findings could inform material science applications in carbon production.

The study used X-ray diffraction to analyze crystal structures. Raman spectroscopy was employed to assess carbon bonding. ATR-FTIR was used to detect functional groups. Anthracite samples were obtained from Zhaotong, China. The samples had high carbon and low ash content. Acid leaching and oxidation were applied to prepare anthracite oxide. The oxidation process involved HNO3 and H2SO4 treatment. Structural changes were compared between raw and oxidized anthracite.

XRD results showed anthracite crystallites have intermediate structures. The structure order degree was between graphite and low metamorphic coals. The average crystallite diameter (La) was higher than in bitumite and lignite. Oxidation caused crystal edges to curl and break. CO groups and HNO3/H2SO4 intercalation occurred at crystal edges. Interlayer spacing increased from 0.351 to 0.361 nm. The number of stacked layers decreased from 6 to 4.5 due to exfoliation. Raman spectroscopy showed increased ID1/IG from 1.9 to 2.0. FWHM of G bond increased from 63 to 68. D2 bond intensity rose from 10.26 to 13.78.

The authors propose that oxidation modifies anthracite's structure in two steps. Edge destruction and intercalation reduce lateral crystal sizes. Increased interlayer spacing and exfoliation were observed. New functional groups like —C—O— and —NO2 were generated. The oxygen-containing functional groups decreased from 0.11 to 0.42. Aromaticity (fa) increased in the oxidized anthracite. Structure order degree decreased, indicating disorder. Active reaction sites were generated during oxidation. These findings suggest anthracite oxide has potential in porous carbon applications.