Process Optimization and Structural Analysis of Humic Acid Extracted from Low-Rank Coal in Xinjiang, China.

Area of Science:

• * Coal Chemistry and Utilization
• * Organic Geochemistry
• * Materials Science

Background:

• * Xinjiang, China, possesses abundant low-rank coal, primarily used as fuel, limiting its high-value utilization.
• * Humic acids, key components of low-rank coal, offer significant potential for value-added applications.
• * Developing efficient extraction methods is crucial for unlocking the potential of these coal resources.

Purpose of the Study:

• * To optimize the alkaline hydrothermal extraction of humic acids from lignite sourced from four distinct regions in Xinjiang.
• * To investigate the structural characteristics of the extracted humic acids.
• * To establish a theoretical foundation for the high-value utilization of Xinjiang's low-rank coal.

Main Methods:

• * Lignite samples from Akesu, Naomaohu, Dananhu, and Santanghu regions were used.
• * Alkaline hydrothermal extraction was employed, with process optimization via orthogonal experimental design.
• * Humic acid yield was analyzed, and structural characteristics were determined using elemental analysis, spectroscopy (UV-vis, FT-IR, XPS), and X-ray diffraction.

Main Results:

• * Optimized extraction yielded 76.31% (Akesu), 64.98% (Naomaohu), 41.33% (Dananhu), and 63.53% (Santanghu) humic acids.
• * Significant variations in aromaticity and structural condensation were observed among humic acids from different regions.
• * Santanghu-sourced humic acid exhibited the highest degree of aromaticity.

Conclusions:

• * An optimized alkaline hydrothermal process for efficient humic acid extraction from Xinjiang lignite was developed.
• * The study demonstrates the feasibility of high-value utilization of low-rank coal resources in Xinjiang.
• * Characterization data provides insights into regional variations in humic acid structure, informing targeted applications.