Modeling the acid-base properties and metal complexation of humic substances with the Stockholm Humic Model
2001 (English)In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 244, no 1, 102-112 p.Article in journal (Refereed) Published
To describe the binding of protons and metals to humic substances, the Stockholm Humic Model (SHM) has been developed. The model employs a discrete-site approach similar to that of Model V/VI, although it has another electrostatic submodel, based on the Basic Stern concept. An empirical set of equations has been introduced to account for the extra screening of charge inside the gel-like structures of the humic substances. Six adjustable parameters are needed to describe proton binding to humic or fulvic acids. To simulate metal binding, equilibrium constants are defined for mono- and bidentate coordination and an extra parameter, Delta LK2, accounts for binding-site heterogeneity. It is shown that the SHM appears to be able to describe proton binding well; the quality of the fits is similar to those obtained by Model V/VI and the NICA-Donnan model. The SHM was capable of correctly describing metal binding and competitive interactions over a wide range of conditions, although the model performance was not very convincing concerning the ionic strength dependence of metal binding and stepwise proton-metal exchange stoichiometries.
Place, publisher, year, edition, pages
2001. Vol. 244, no 1, 102-112 p.
model, humic acid, fulvic acid, metal, complexation, lead, cadmium, calcium, counterion condensation theory, poly-electrolyte properties, simple electrostatic model, ion-binding model, fulvic-acid, proton binding, physicochemical description, potentiometric titrations, cation binding, copper-binding
IdentifiersURN: urn:nbn:se:kth:diva-21137DOI: 10.1006/jcis.2001.7871ISI: 000172465700014OAI: oai:DiVA.org:kth-21137DiVA: diva2:339834
QC 201005252010-08-102010-08-10Bibliographically approved