Characterization and Interaction of Humic Acids with Metal Ions as a Function of Solution pH

This study examines the solubility of humic acids as a function of solution pH and their interactions with di- and trivalent metal ions at different pH values. It has been observed that humic acids and their salts interact with divalent transition metal ions in aqueous solutions at low pH values. The results demonstrate that the amount of metal ions – specifically copper, cobalt, and nickel – bound to humic acids increases almost linearly with their initial concentration. Moreover, the amount of bound metal ions rises as the pH of the medium increases. Investigations into the interactions of iron, aluminum, and chromium ions with humic acids at varying pH levels show that, at low pH values and low metal ion concentrations, the amount of metal ions bound to humic acids is directly proportional to their concentration in the aqueous solution.