Rank-Dependent Amphiphilicity of Coal: Insights into Combustion and Beneficiation Mechanisms

This study investigates the amphiphilic nature of coal through a detailed spectroscopic analysis, employing FT-IR and XPS to examine the chemical and microstructural transformations from lignite to semianthracite rank of coals. By analyzing hydrophilic and hydrophobic functional groups across varying coal ranks, this research provides insights into how compositional differences impact coal's surface properties, which ultimately impact the industrial utilization of these coals. Findings demonstrate that hydrophobicity increases with coal rank, correlating to rising C-H and C-C areas, while hydrophilic groups such as CO, C-O, and COO- decline gradually. These results offer a basis for developing screening criteria based on the moisture content and functional group distribution, facilitating the identification of high-quality coal with optimal combustion characteristics. It also provides a comprehensive understanding of the role of surface amphiphilic characterization for coal beneficiation processes across different ranks of coal. Additionally, the paper presents a new formula to represent the hydrophobicity of the sample based on the contribution (%) of C-C bonds.