Binding of cadmium to Laurentide fulvic acid. Justification of the functionalities assigned to the predominant acidic moieties in the fulvic acid molecule

The binding of cadmium to a fulvic acid (FA) extracted from peat was studied as a function of pH (4-8), ionic strength (0.01 and 0.10 M NaNO3) and ratio of fulvic acid to metal ion concentrations (FA/Cd = 8, 4, and 2). An overall complex formation function of approximately 10(3.14) was determined to enable comparison with previous studies. Additionally, literature values of complex formation constants were employed to describe the interaction between Cd(II) and the individual acidic sites. A good prediction of the experimental results is considered as a justification of the functionalities assigned to the predominant acidic sites in the fulvic acid molecule.