Metal Ion Binding by Humic Acid: Application of the NICA-Donnan Model

作者：David G. Kinniburgh, Christopher J. Milne, Marc F. Benedetti, José Paulo Pinheiro, Jeroen D. Filius, Luuk K. Koopal, Willem H. Van Riemsdijk · 发表于：Environmental Science & Technology · 年份：1996 · DOI：10.1021/es950695h · 被引用次数：556 · 研究领域：Environmental Toxicology and Ecotoxicology、Heavy metals in environment、Analytical chemistry methods development

A Donnan-type model for nonspecific binding of electrolyte ions has been combined with the non-ideal competitive adsorption (NICA) model for specific binding to produce a model for ion binding to humic substances. The model considers site heterogeneity, non-ideality, multicomponent competition, and electrostatic interactions. The NICA-Donnan model was fitted to data for H, Ca, Cd, Cu, and Pb binding by a purified peat humic acid. The model fits were good and covered a wide range of pH and free metal concentrations. The parameters from these single metal data sets were then used to predict the competitive effect of Ca on Cd and Cu binding at various pHs. These predictions agreed well with the experimental data although there were some small but systematic differences. The new NICA-Donnan model also predicted reasonably well the increase in Cd and Cu binding on changing from a 0.1 M KNO 3 background electrolyte to 0.01 M KNO 3 . A shortcoming of the model is that in some cases it significantly underestimated the H + /M 2+ exchange ratio, especially at high pH and for Cu binding.