Abstract
This article presents the synthesis and comparative characterization of humic acids extracted from brown coal deposits of Kuznetsk and Kumuskuduk in Kazakhstan. Advanced analytical techniques, including infrared (IR) spectroscopy, elemental analysis, and thermogravimetric/differential scanning calorimetry (TGA/DSC), were employed to investigate the physicochemical and structural properties of the humic acids derived from these two distinct geological sources. The results revealed significant differences in elemental composition, particularly in carbon, oxygen, and hydrogen content, which were directly related to the geological and environmental conditions under which the coals were formed. Variations in the concentration of carboxyl and hydroxyl functional groups were also identified, influencing the sorption capacity, acidity, and complexation behavior of the humic acids. Thermal analysis demonstrated differing levels of thermal stability and decomposition patterns, reflecting the structural heterogeneity of the samples. This study highlights the importance of geological origin in determining the functional potential of humic substances and supports their application in environmental remediation, agriculture, and water purification.