THE USE OF SELECTIVITY COEFFICIENTS TO ESTIMATE MODIFIED LANGMUIR ISOTHERM PARAMETERS AS A FUNCTION OF EXPERIMENTAL CONDITIONS

Modified Langmuir isotherm parameters (K(D) and beta) were fitted to e xperimentally determined selectivity coefficients to test a derived re lationship between them. Reasonable estimates of K(D) and beta values were obtained for a wide range of assumed solid-liquid ratios (W/V) an d initial concentrations of competing solute (C(BO)). The results indi cate that at low initial concentrations K(D) decreases and beta increa ses as C(BO) increases. A more pronounced effect is observed at lower W/V values for K(D) and at higher W/V values for beta. At low C(BO) va lues, both K(D) and beta decreases as W/V increases. At higher C(BO) v alues, K(D) and beta are not affected by W/V. Results also indicate th at a linear K(d) can be strongly affected by W/V and C(BO); the effect of both parameters have been documented in the literature. The relati onship between the modified Langmuir isotherm parameters and experimen tally determined selectivity coefficients provides a method that optim izes the information obtained from the adsorption modeling of experime ntal data.