Physicochemical Studies of the Humic, Hymatomelanic and Fulvic Acids of Brown Coals

The procedure for obtaining humic (HA), hymatomelanic (HmA) and fulvic acids (FA) that allows achieving their high yield has been developed and tested with the brown coals of the Kansk-Achinsk and the South Ural basins. The highest yield of humic substances is achieved for naturally oxidized brown coal of the Tisul deposit: HA - 68.0%, HmA - 11.3%, FA - 9.6%. The composition of native brown coals, as well as HA, HmA and FA obtained from them, was studied using proximate and ultimate analysis, FTIR spectroscopy and C-13 NMR (CPMAS) spectroscopy. It is established that the chemical and structural-group composition of HA, HmA and FA has significant differences. The samples of HmA and FA are characterized by relatively high content of oxygen-containing aliphatic groups with the predominance of carboxylic acids and esters in comparison with HA. Higher content of carbon, hydrogen and aromatic fragments is characteristic of HA. The samples of HmA and FA have similar elemental and structural group composition, however, HmA has a higher content of carbon and aromatic frag