Modifications in the solubility and precipitation behavior of various metals as a result of their interaction with sedimentary humic acid

The sedimentary humic acid or its acid-hydrolysate, consisting of various amino acids, was found effective in dissolving unusually large quantities of metals (up to 682 mg/g of organic matter) from their insoluble salts. The presence of humic acid in the reaction media which had favorable conditions for the precipitation of metals as carbonates, hydroxides or sulfides, prevented the formation of insoluble metal salts. Infrared analysis suggests that the metals added to various anionic systems and humic acid do not react with the anion. The most likely mechanism of reaction appears to be a complex formation between metals and organic matter which keeps the metal in solution.The enhanced solubility and consequent decrease in precipitation of metals under the influence of humic compounds, as evidenced in these studies should play a leading role in the accumulation of metals in sedimentary deposits.