Temperature Dependences of IR Spectra of Humic Substances of Brown Coal

The capabilities of temperature-monitored IR spectroscopy for studying the organic matter and mineral composition humic substances (HS) were tested. Temperature dependences mid-IR spectra heated in air range 25–215 °C (298–488 K, with a step 2.5 °C)—for three commercially available samples isolated from brown coal (leonardite)—were performed. characteristic bands identified, their changes band maxima positions intensities compared. From viewpoint interpretation HS components, divided into regions quartz lattice region (800–260 cm?1), overtone (1270–800 substance (1780–1270 combination (2800–1780 CH-speciation (3100–2800 hydrogen-speciation (4000–3100 cm?1) thus selected to contain dominating type bands. For first time, reversible change frequencies upon heating was observed, which can be interpreted as forming structures particular order studied dry state. single sample, both band-shift scale functional dependence various on temperature differ significantly. approach differentiates crystalline bands, amorphous silica, HSOM/surface groups experiencing different behavior intensities. Band-maximum considered more stable experimental conditions than at temperature, providing detailed structure analysis without decomposition or destruction.