BINDING OF PROTONS AND METAL-IONS IN HUMIC-ACID - TEST OF THE BIMODAL GAUSSIAN DISTRIBUTION MODEL

A continuous multiligand pH-independent model was applied to the binding of protons and metal ions to humic acids; this model is essentially based on a bimodal Gaussian distribution of binding sites and allows the calculation of metal binding constants which are pH independent and representative of true thermodynamic values. The meaning of the distribution variance is briefly discussed and results of the application of the model to copper titration are reported.