The impact of integrated nanofiltration and electrodialytic processes on the chemical composition of sweet and acid whey streams

Abstract

High content of minerals and organic acids poses problems with further utilization of the whey, especially acid whey streams. Thus, preliminary desalination and deacidification of the whey is a necessary step before further processes. In this work the effect of the desalination of two types of whey by nanofiltration followed by electrodialysis is demonstrated. Mineral profile of the whey as well as content of the main organic acids at each stage of desalination are analyzed. It is shown, that during nanofiltration the mineral content reduces up to 27–28% for both types of whey, thereby the efficiency of cation removal decreases as follows K+~Na+≫Ca2+>Mg2+, among anions the highest reduction was noted for monovalent Cl−. Followed electrodialysis increases desalination degree up to 88% for sweet whey and 91% for acid whey, which provides a high removal of minerals and organic acids. It is shown that content of lactic acid in acid whey decreases by 35% after nanofiltration and by 88% after combination of nanofiltration and electrodialysis. The differences in ions reduction during the processes between two types of whey are noticed. Acid whey powders with different desalination degrees are analyzed. The water content, average particle size and degree of aggregation are lower when the degree of the desalination of feed whey is higher.