Solid-Phase Reactions of Humic Acids with Sodium Percarbonate as a Way to Study Processes Occurring on the Mechanochemical Oxidation of Brown Coal

The reactions of humic acids in a pure form and in the composition of coal with sodium percarbonate occurring on solid-phase mechanochemical treatment were compared. Analysis for CHNO, IR spectroscopy, and potentiometric titration were used to study changes in the composition of humic acids mechanochemically treated after isolation from brown coal. The sorption properties in relation to heavy metal ions (Zn²⁺, Cu²⁺, and Cd²⁺) and their changes as a result of the treatment were studied. The results were correlated with data similar to those for humic acids in coal that underwent mechanochemical treatment. It was demonstrated that, at present, an increase in the yield of humic acids and the concentrations of phenolic and carboxyl groups in brown coal as a result of treatment with sodium percarbonate can be explained by the oxidation of fractions other than humic acids in the organic matter of brown coal.