When an ion-exchange chromatography process is employed for the recovery of potassium clavulanate (KCA) from fermentation broth, the resulting KCA solution usually contains a large amount of KCl due to the use of a concentrated elution buffer. In this study, nanofiltration (NF) with NF200 membrane has been carried out in a diafiltration (DF) mode to remove KCl from the ion-exchanged KCA solution, and a multistage version NF model has been proposed to represent this process. In this model, the effect of temperature on clavulanate degradation during the filtration has been incorporated. For the determination of model parameters associated with NF and clavulanate degradation, separate series of experiments at different concentrations, pressures and temperatures were performed. The clavulanate rejection could be assumed to be constant with no loss of modeling accuracy based on the experimental data. The chloride rejection was represented as a function of its concentration simply by nonlinear fitting. For the estimation of solution flux, the reflection coefficient and effective volume charge density were calculated by using the Speigler-Kedem model together with the Teorell-Meyer-Sievers model. Model prediction of clavulanate and chloride concentration profiles was in good agreement with the experimental data. It was also demonstrated that KCl could be removed effectively by NF in a DF mode. (c) 2009 Elsevier B.V. All rights reserved.