Modeling of Ammonium Lactate Recovery and Sulfate Removal from Model Solution by Nanofiltration

Abstract

In this study, Nanofiltraiton with TFC-SR2 was employed in a continuous mode to recovery ammonium lactate from a model solution. A modeling method based on multistage version of NF process has been proposed to represent this process. For the estimation of model parameters associated with the NF process under consideration, experiments at different concentrations and operating pressures were performed. The lactate rejection at the given pressure was empirically represented as a function of its concentration by nonlinear curve fitting. For the determination of solution flux, the reflection coefficient and effective volume charge density were calculated by using the SK model together with the Teorell–eyer–ievers model. Time profiles of lactate concentration in the system and permeate predicted by the proposed model were in a good agreement with the experimental data. Major impurity such as sulphate ion in fermentation broth was retained by the NF with TFC-SR2 membrane. From prediction of impurity profile by using modified NF model containing parameters of each impurity rejection, it was known that impurity was accumulated in the system. To prevent membrane fouling by impurity accumulation, bleeding step which is to draw off the concentrated solution was necessary. Simulation of impurity profile as bleeding was carried out by using modified NF model with bleeding step. Through this result, it could be confirmed that impurity concentration decreased proportional to bleeding percentage, while recovery rate of lactate ion was lowered. So, the utilization of the model for simulation study will be addressed, to select optimal process options and to optimize process conditions with consideration of the lactate yield and the accumulation of major impurities.