Formation of Humic Colloids in Aqueous Solutions at Different pH Values

The effect the mechanochemical modification of humic acids has on their surface-active and acid–base properties is studied. The dependence of the surface activity of humic acids on structural changes, concentration, and the pH of the medium are determined. It is shown that in an alkaline medium, associates of humic acids are characterized by the minimum average particle radius, an increased degree of dissociation of acidic groups, and enhanced surface activity at the gas–liquid interface. A neutral or acidic medium facilitates aggregation and an increase in the size of macromolecules of humic acids.