Optimal Parameters for the Production of Humic Acids from Brown Coals with Specific Structural-Group Composition

The effect of alkaline extraction parameters on the yield, biological activity, and functional group composition of the humic acids (HAs) of brown coals was investigated. It was found that the functional group composition of the HAs can be intentionally affected by varying alkaline extraction parameters (the amount of an alkali and the duration and temperature of the process). The biological activity of humic preparations in the form of sodium humates as functions of the following structural group parameters was determined: the degree of aromaticity ( f(a)) and a parameter reflecting the ratio between aromatic and aliphatic fragments in the organic matter of humic acids ( f(a/al)). It was established that the milder the conditions of alkaline extraction, the lower the yield of HAs, but the higher their degree of aromaticity ( f(a)) and biological activity.