Conditional stability constants and binding capacities for copper (II) by ultrafilterable material isolated from six surface waters of Wyoming, USA

Abstract

Ultrafilterable material < 0.15 #m was collected from six Wyoming surface waters, for which the chemical limnology had also been determined. The material was separated into four nominal size-fractions and the binding capacity of each for copper was determined by a hyperbolic, site-saturation model. The conditional, overall, thermodynamic stability constants (K') for binding of copper were determined by two discrete models: The one-and two-component Scatchard functions, and two continuous multiligand models; The one-and three-component Gaussian Scatchard functions. The accuracy of the stability constants to predict the speciation of Cu(II) in the titration of the isolated fractions and of whole waters was evaluated by comparing the predictions of the thermodynamic, geochemical simulation model, GEOCHEM to those measured by selective ion electrode. The Cu-binding capacity of material retained by ultrafilters was positively correlated with the hardness and alkalinity of the surface waters, from which they were isolated as well as the percent ash content of the ultrafilter-retained material. The magnitude of the conditional stability constant (Ki') decreased as the ratio of the total Cu concentration to total concentration of Cu-binding sites increased. The cumulative frequency distribution of K,' was lognormally distributed. All four of the models used to estimate the conditional stability constants gave reasonable prediction of the speciation of Cu for both fractionated and whole waters but, depending on the situation, the one-or two-component Scatchard estimate generally gave the best predictions of the proportion of copper, which would be expected to be bound.

Characterization of Immobilized Poly(l-cysteine) for Cadmium Chelation and Preconcentration

“…Estimates were made for the strong sites competitive with EDTA or en as expressed by where CdPLC and PLC represent the bound Cd and free PLC-CPG, respectively. Scatchard analysis has been used to estimate conditional stability constants for metal binding by proteins as well as for metal binding with more heterogeneous materials such as algae and humic−fulvic acid mixtures. , Since more than one type of binding site was present on PLC-CPG, a multiple site Scatchard model, represented by eq 2, was used to determine average stability constants and site capacities where [CdA] is the total metal bound to the column and K i and n i represent the stability constant and the site capacity for the i th site, respectively.…”