
TY  - JOUR
A1  - Spark, K. M. 
A1  - Wells, J. D. 
A1  - Johnson, B. B. 
T1  - The interaction of a humic acid with heavy metals
JF  - Soil Research
JO  - Soil Res.
Y1  - 1997
VL  - 35
IS  - 1
SP  - 89
EP  - 102
KW  - copper, zinc, cobalt, cadmium, sorption, solubility.
UR  - https://doi.org/10.1071/S96008 
N2  - The solubility of a coal humic acid and the sorption of heavy metals (Cu(II), Zn(II), Co(II), and Cd(II)) in the absence and presence of the humic acid were determined as a function of pH and concentration of background electrolyte. The solubility of the humic acid at low electrolyte concentration increases in a 2-step process with increase in pH. About 80% dissolves in the pH region 3&#8211;8&#183;5, and the remainder in the region pH &#62;8&#183;5. The sorption of metals occurs at pH values significantly lower than those associated with the formation of insoluble metal hydroxides, with a maximum occurring in the pH region 5&#183;5&#8211;7&#183;5, and involves the solid state fraction of the humic acid. At the higher electrolyte concentration, the solubility of the humic acid is again a 2-step process but the increase in acid solution occurs over a relatively narrow pH range (5&#8211;6). At high pH, the presence of the humic acid significantly reduces the precipitation of the metals at both low and high salt concentration, probably due to the formation of soluble metal&#8211;humate species. There is evidence to suggest that the major functional group of the humic acid with which the metal cations interact is the carboxyl group. 
ER  -

