Full Length ArticleComplementary analyses of infrared transmission and diffuse reflection spectra of macerals in low-rank coal and application in triboelectrostatic enrichment of active maceral

•Manual purification of coal macerals without chemical demineralization.•Complementary analyses of infrared transmission and diffuse reflection spectra of macerals.•Surface structures comparison of vitrinite and inertinite based on quantitative analysis of diffuse reflectance spectra.•Macerals triboelectrostatic separation behavior analyses from the aspect of the surface functional groups.

Fourier infrared analyses of coal mostly adopted KBR compression method currently. However, infrared spectra obtained by this technique will suffer the interference of water absorption band. For a comprehensive knowledge of macerals in low-rank coal, complementary analyses of KBR compression and diffuse reflection methods were conducted in this investigation. Other researches of coal liquefaction have shown that vitrinite and inertinite are the active and inert component respectively in the coal liquefaction and improvement of vitrinite content in coal will enhance the liquefaction efficiency. Triboelectrostatic separation was performed to easily liquefied low-rank coal, and the active component vitrinite content of negative coal flow was increased markedly. This study compared surface structures of vitrinite and inertinite based on quantitative analysis of diffuse reflectance spectra and researched their triboelectrostatic separation behavior from the surface functional groups angle. Inertinite possesses high concentrations of oxygen-containing groups and hydrophilic groups (phenolic hydroxyl and carboxyl) while vitrinite has high content of hydrophobic groups (alkyl groups and long carbon chain), which indicate they could be separated and enriched at some degree by triboelectrostatic beneficiation at the condition of high-temperature and low relative humidity.