Metal Ion Binding by Humic Acid: Application of the NICA-Donnan Model
- 1 April 1996
- journal article
- Published by American Chemical Society (ACS) in Environmental Science & Technology
- Vol. 30 (5), 1687-1698
- https://doi.org/10.1021/es950695h
Abstract
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 KNO3 background electrolyte to 0.01 M KNO3. A shortcoming of the model is that in some cases it significantly underestimated the H+/M2+ exchange ratio, especially at high pH and for Cu binding. \uKeywords
This publication has 32 references indexed in Scilit:
- Models for Association of Metal Ions with Heterogeneous Environmental Sorbents. 1. Complexation of Co(II) by Leonardite Humic Acid as a Function of pH and NaClO4 ConcentrationEnvironmental Science & Technology, 1995
- Design and Construction of a Personal‐Computer‐Based Automatic TitratorSoil Science Society of America Journal, 1995
- Potentiometric Titrations of Humic Substances: Do Ionic Strength Effects Depend on the Molecular Weight?Environmental Science & Technology, 1995
- Metal Ion Binding to Humic Substances: Application of the Non-Ideal Competitive Adsorption ModelEnvironmental Science & Technology, 1995
- Humic acid complexation of calcium and copperEnvironmental Science & Technology, 1988
- General purpose adsorption isothermsEnvironmental Science & Technology, 1986
- Metal-humate interactions. 2. Application and comparison of modelsEnvironmental Science & Technology, 1986
- Metal-humate interactions. 1. Discrete ligand and continuous distribution modelsEnvironmental Science & Technology, 1986
- A unified physicochemical description of the protonation and metal ion complexation equilibria of natural organic acids (humic and fulvic acids). 3. Influence of polyelectrolyte properties and functional heterogeneity on the copper ion binding equilibria in an Armadale Horizons Bh fulvic acid sampleEnvironmental Science & Technology, 1986
- A unified physicochemical description of the protonation and metal ion complexation equilibria of natural organic acids (humic and fulvic acids). 1. Analysis of the influence of polyelectrolyte properties on protonation equilibria in ionic media: fundamental conceptsEnvironmental Science & Technology, 1986