Modeling of potassium lactate recovery and impurity removal from food waste fermentation broth by nanofiltration

Abstract

A mathematical model of continuous nanofiltration process has been proposed for the recovery of lactate from fermented food waste. Two different types of model: one consisting of a differential equation and the other of multistage version. A nanofiltration membrane of TFC-SR2 was used for the treatment of simulated fermentation broth instead of actual one to establish a fully identified environment for the experiments. To determine the model parameters, a series of experiments were conducted at various concentrations of lactate and operating pressures using calcium hydroxide as the main impurity. The rejection of calcium could be assumed to be constant, while lactate rejection could be well represented as a function of its concentration. To predict the solution flux, the reflection coefficient and volume charge density were estimated by using the Speigler-Kedem model and the Teorell-Meyer-Sievers model. Model predictions were in good agreement with the experimental data for both transient and steady states. In order to improve model reliability, a sensitivity analysis was performed. A simulation study by using the proposed model was also performed to predict the effects of the bleed ratio on the lactate recovery and impurity accumulation in the system. Although the present model has been proposed for a continuous process, it can be easily applied after a modification to other types of lactate recovery such as batch process and nanofiltration process in a diafiltration mode.