How Overlimiting Current Condition Influences Lactic Acid Recovery and Demineralization by Electrodialysis with Nanofiltration Membrane: Comparison with Conventional Electrodialysis

Abstract

Acid whey is the main co-product resulting from the production of fresh cheeses and Greek-type yogurts. It generally goes through a spray-drying process prior to valorization, but it needs to be deacidified (lactic acid recovery) and demineralized beforehand to obtain a powder of quality with all the preserved compounds of interest such as lactose and proteins. Electrodialysis (ED) is a process actually used for acid whey treatment, but scaling formation at the surface of the ion-exchange membrane is still a major problem. In this work, a combination of two new avenues of ED treatment has been studied. First, the integration of a nanofiltration (NF) membrane in an ED conventional stack was compared to a classical ED stack with an anion-exchange membrane in a standard current condition. Secondly, both configurations were tested in the overlimiting current condition to study the impact of electroconvective vortices on process efficiency. The combined effects of the NF membrane and overlimiting current condition led to a higher lactic acid recovery rate of acid whey (40%), while the conventional ED stack in the overlimiting current condition led to a higher demineralization (87% based on the total cation concentration). Those effects were related to the conductivity, pH, global resistance, and energy consumption of each treatment that are influenced by water splitting phenomenon, which was decreased in the overlimiting condition.

Electrodialytic Processes: Market Overview, Membrane Phenomena, Recent Developments and Sustainable Strategies

“…Consequently, such an induced increase of temperature in overlimiting condition could be a potential advantage. Indeed, as demonstrated very recently by Beaulieu et al [ 90 ], it would improve the transfer of ions. However, according to these authors, the use of an overliming current condition coupled with the temperature increase induced did not improve the energy efficiency of the process.…”

“…In parallel these conditions would maintain or increase the relative energy consumption by increasing the mass transfer enhanced by the constant presence of vortices. Such conditions would then take advantage of the overlimiting conditions (vortices, decrease in polarisation concentration and increase in mass transfer) without the inconvenient linked to a greatly higher relative energy consumption [ 90 ].…”

“…They concluded also that electrodialysis in an overlimiting condition seems to be more advantageous than in an underlimiting one, but they did not evaluate the energy consumption of both processes [ 91 ]. In addition, on acid whey demineralization and lactate recovery, Beaulieu et al [ 90 ] studied the impact of electroconvective vortices on ED process efficiency. They compared the ED process both in underlimiting and overlimiting current conditions in terms of demineralization, lactate recovery, ion migration, temperature increase, overall system resistance and energy consumption.…”

“…More recently, Ge et al exemplified such a selective cation fractionation of EDNF with H + /Zn 2+ and Na + /Mg 2+ systems and demonstrated that an NF membrane can increase the limited current density in ED [ 250 ]. In 2020, EDNF was tested for acid whey demineralization and simultaneous lactate recovery in under- and over-limiting conditions [ 90 ]. The integration of a nanofiltration (NF) membrane in an ED conventional stack led to a similar lactate recovery rate than conventional ED (around 29% in 60 min) with respective demineralization rates of 20.3% and 50.8%.…”

Recent Advances on Purification of Lactic Acid

“…Despite the recent advances in membranes, they have the fundamental problem of membrane fouling. [135,136] The particles in water adsorb or deposit on the membrane surface due to physical and chemical function, the accumulation of these particles can cause concentration polarization. [137] The concentration of the membrane surface is higher than that of the liquid phase, forming a gel layer, which reduces or blocks membrane pores, thereby leading to a decrease of membrane flux and poor separation abilities.…”