Fouling investigation of the bipolar membrane during electro-acidification of skim milk using X-ray micro-computed tomography

Introduction. Electrodialytic processes have become relevant technology in promoting sustainability within the food industry. Bipolar membrane electrodialysis (EDBM) offers an efficient and eco-friendly alternative for skim milk (SM) acidification, eliminating the need for added acids that affect milk properties and mineral composition [1-2]. In this study, the fouling behavior of bipolar membranes (BMs) during the electroacidification process of skim milk was investigated. The findings provide valuable insights into the foulingbehavior of BMs during the electro-acidification of milk, offering guidance for improving process efficiency and product quality [3].Experimental/methodology. EDBM was carried out with an ED unit (MemBrain s.r.o., Czechia) at 20°C. The membrane stack contained 6 pairs of cation-exchange membranes (CMs) and BMs with an active surface area of 0.0384 m2 in CM-BMCM configuration. X-ray micro-computed tomography (mCT) X-ray MicroCT EasyTom 150 (RX Solutions, Chavanod, France) was used to investigate the pristine and fouled BMs after the EDBM acidification of SM at 20°C. Results and discussion. The pH was decreased from 6.7 to 5.8, when the water molecules split under current into H3O+ and OH‒ at the interfacial layer of the BMs, while water diffused through monopolar layers to the interfacial layer. The fouled BM showed much different characteristics than the pristine. The fouling layer on the cation exchange layer of BM looks rough and does not have the same thickness over the entire membrane area. It was found, that the most striking difference is the pore distribution in the fouled membrane. Still, both layers contain pores that are not connected, but their amount was drastically reduced as compared to thepristine membrane [3].Acknowledgments This research was funded by The Platform for Novel Gentle Processing supported by the Dairy Rationalisation Fund (DDRF), University of Copenhagen and Arla Foods. References [1] Bazinet, L. et al. Journal of Agricultural and Food Chemistry 2001, 49, 2812-2818.[2] Gagnon, R.D. et al. Membranes 2022, 12, 270.[3] Merkel, A. et al. Journal of Membrane Science 2024, 694, 122429.