Changes in the Composition of Humic Acids under Exposure to Dielectric-Barrier Discharge Plasma

The composition and properties of humic acids (HAs) isolated from oxidized brown coal at pH 2 and pH 7, processed in dielectic-barrier discharge plasma in air, have been studied. With an increase in the active discharge power from 11 to 22 W, the C/N atomic ratio and the number of $${\text{NO}}_{2}^{ - }$$ groups in the structure of HAs isolated at pH 2 increases, while the concentration of ArCOOH groups decreases. The antioxidant activity of HAs in a neutral medium also increases with the active discharge power.