Structural-Group Composition and Biological Activity of Humic Acids Obtained from Brown Coals of Russia and Mongolia

Abstract

The biological activity of humic preparations in the form of sodium and potassium humates was investigated depending on the structural group parameters of humic acids (HAs): the degree of aromaticity (f_a), a hydrophilic–hydrophobic parameter (f_hh), and a parameter reflecting the ratio between aromatic and aliphatic fragments in the organic matter of HAs (f_ar/al). Native and modified HAs isolated from peat and brown coals of Russia and Mongolia, the composition of which was characterized using proximate and ultimate analysis and ¹³С NMR (CP MAS) spectroscopy, were used as preparations. It was established that modification by destructive alkylation and the subsequent bitumen removal changed the structural-group composition of HAs, increased the degree of aromaticity, and led to an increase in their biological activity.