Structural Modification of Humic Acids in a Barrier Discharge Plasma

The paper presents the results of the initiation of chemical transformations of humic acids (HA) in a barrier discharge plasma. The HA were treated with ammonia vapor in the presence of various gaseous media like ethylene, air, oxygen, carbon dioxide, and mixtures of argon. The method of EPR spectroscopy has revealed a decrease in the number of paramagnetic centers after treatment of HA in a barrier discharge. This suggests the recombination of free radicals in their structure. As revealed by IR spectroscopy, the intensity of the band at 1383 cm⁻¹ corresponding to the NO₃ group increased when HA were exposed to discharge plasma in air. When HA were treated with ammonia vapor in an argon atmosphere, ammonium humate was formed, which is completely soluble in water.