Effect of reverse osmosis pre-processing of acid whey and electrodialysis current density on process performance

Funding Information: The authors would like to thank the staff of Hobro dairy for collection of acid whey. The present study is a part of the Platform for Novel Gentle Processing supported by the Dairy Rationalisation Fund ( DDRF ), Copenhagen University and Arla Foods . Publisher Copyright: © 2023 The AuthorsAcid whey (AW) is the main side-stream from acidified dairy products, known for its high contents of lactic acid and minerals. The present work investigates the effect of reverse osmosis (RO) pre-processing of AW (ROAW) and the current density during electrodialysis (ED) on the ED process performance. Firstly, the limiting current density of the ED system when treating AW and ROAW was determined. Then, the AW and ROAW have been demineralized and deacidified at under-limiting or over-limiting current density batch operating conditions. RO pre-processing of AW and current density strongly affect the demineralization rate and solutes mass transport across the membranes. Lactate transport can be rationalized by the weak acid dissociation mechanism, while water splitting played a minor role in the ED process performance. Among cations, calcium and magnesium were most affected by RO pre-processing, due to their high affinity to the cation exchange membranes. Lactose and galactose were found in small amounts in the concentrate solution, while no glucose was detected for most conditions even though the glucose content decreased in the diluates.publishersversionpublishe

Fouling of ion-exchange membranes during electrodialytic acid whey processing analysed by 2D fluorescence and FTIR spectroscopy

Funding Information: The authors would like to thank the staff at Hobro dairy for collection of acid whey samples. Also, special thanks to MemBrain s.r.o. and MEGA a.s. for providing us with the electrodialysis unit and the ion-exchange membranes. This present study is a part of the Platform for Novel Gentle Processing supported by the Dairy Rationalisation Fund (DDRF), Copenhagen University and Arla Foods. This work received support from PT national funds (FCT/MCTES, Fundação para a Ciência e Tecnologia and Ministério da Ciência, Tecnologia e Ensino Superior) through the projects UIDB/50006/2020 and UIDP/50006/2020. Publisher Copyright: © 2023 The Author(s)Acid whey (AW), a by-product from the production of acidified dairy products, contains high amounts of lactic acid and minerals that can be recovered by electrodialysis (ED). To better understand the process and improve its efficiency, the objective of this study was to investigate fouling of ion-exchange membranes (IEMs) during ED of AW and concentrated AW by reverse osmosis (ROAW), underlimiting (ULCD), limiting (LCD) and overlimiting current density operating conditions (OLCD). The structure, hydrophobicity, and chemical composition of membranes showed differences regarding fouling on anion- (AEM) and cation- (CEM) exchange membranes facing the diluate and the concentrate, both for AW and ROAW. Furthermore, operating at OLCD tends to reduce fouling compared to ULCD, due to the expected generation of electroconvective vortices. 2D fluorescence spectroscopy and Fourier-transform infrared spectroscopy (FTIR) provided complementary and more detailed information regarding the fouling and efficiency of the cleaning procedure. The 2D fluorescence spectra showed that the AEM surfaces in contact with the diluate change more than those in contact with the concentrate. The FTIR analyses showed the presence of lactose and lactic acid on the AEM surfaces in contact with the concentrate, which could not be detected by fluorescence.publishersversioninpres

Determination of Local Heat-Transfer Coefficients Around a Circular Cylinder Under an Impinging Air Jet

Determination of Local Heat-Transfer Coefficients Around a Circular Cylinder Under an Impinging Air Je

The role of processing parameters on energy efficiency during microwave convective drying of porous materials.

A small-scale microwave convective dryer was built to study the effects of microwave power level, air temperature, and air velocity on drying kinetics, temperature development, and specific energy consumption (MJ/kg evaporated water) using statistical designs. Increased microwave power had a large significant effect on moisture loss and temperature development and it reduced specific energy consumption. Increased air temperature and air velocity increased specific energy consumption, as their effect on drying kinetics was smaller in the system used. Low air temperature slowed the drying process, without affecting the relationship between average sample temperature and average moisture content during drying