Whey Demineralization: Selective Lactose Concentration by Using Polyelectrolyte Multilayer Hollow Fiber...

Polyelectrolyte multilayers (PEMs) coated on the top of porous supports through layer-by-layer (LbL) assembly have been shown to yield nanofiltration-type membranes with highly tunable properties. The design-selectivity relationship of PEM-based membranes can be exploited for a wide range of applications. In this research, for the first time, PDADMAC/PSS-based membranes were fabricated on hollow fiber supports for whey demineralization. We propose that the designed membranes allow for simultaneous demineralization and lactose concentration during whey processing. Results from single-salt tests show <10% retention for MgCl₂ and CaCl₂, while achieving 95% lactose retention in model solutions. Moreover, the effect of pH conditions was analyzed, revealing that molecular interactions dictate the degree of demineralization. Finally, the designed membranes were tested at different pH conditions using real-life samples, demonstrating that at pH 2.1, 89% lactose retention is achieved with low salt retentions, even for multivalent ions.