The effect of restriction membranes on mass transfer in an electrodialysis with filtration membrane process

Abstract

In an electrodialysis with filtration membrane (EDFM) separation process, a pair of restriction membranes is used to prevent leakage of molecules into the electrode solution. Driven by the electrical potential gradient, ions transport across these membranes in different directions, resulting in concentration changes in the feed and permeate compartments respectively. However, the effects of these restriction membranes have not been systemically studied to date. In the present work, the performance of a non-charged polyacrylamide (PAm) membrane and two ion-exchange membranes were compared. PAm restriction membranes were found to give the most stable operation, with only slight concentration and pH changes in the feed and permeate compartments. The configurations with either cation or anion exchange membranes showed more significant changes in electrolyte concentration in opposing directions but the same pH trend, as the current density increased. The configuration with cation exchange membranes as restriction membranes resulted in the highest protein recovery, while the use of anion exchange membranes would appear as the best choice for separation of a protein with net positive charge. The results of this work provide important insights for the design and operation of EDFM processes and a better understanding of the transport phenomena that occur during the separation of bioactive compounds.

Isolation of lactoferrin and immunoglobulins from dairy whey by an electrodialysis with filtration membrane process

“…The BSA flux obtained in repeat experiments using the CEM restriction membranes was highly variable. Contrary to our prior work [53], there also appeared to be no increase in this flux relative to the use of a PAm restriction membrane. The pH changes observed in our earlier work were much less significant, due to the use of an alternate buffer system.…”

“…Only around half of this absorbed lactoferrin can be desorbed when using a salty water wash. While not discussed in our prior work [53], the use of ion exchange membranes in place of the neutral PAm, is likely to also cause the onset of greater water splitting, which in turn will result in significantly greater energy demand and higher electro-osmotic flows of water. Indeed, the PAm membranes results in less water transfer than when ion exchange membranes are used ( Table 2).…”

“…We also considered the use of ion exchange membranes as restriction membranes, as this is common in EDUF applications [13]. Our earlier work had also indicated that the use of such charged membranes could increase protein recovery by reducing the absorption of charged proteins [53]. When using cation-exchange membranes (CEM) for the restriction membranes, the loss of lactoferrin can be reduced to 0.2 g/m 2 .hr and again this can be recovered during a saltwater wash (Table 2).…”

Electrokinetic desalination of brackish water and associated challenges in the water and energy nexus

“…48 It can also valorize desalination brines to produce acids and bases using bipolar membrane. 21 ED can concentrate (i) precious metals such as lithium 49 and cadmium 50 ions, and (ii) nutrient ions and organic compounds such as citric acid, 51 protein 52 and glycine, 53 from impaired water.…”

Fabrication of MNPs/rGO/PMMA Composite for the Removal of Hazardous Cr(VI) from Tannery Wastewater through Batch and Continuous Mode Adsorption

“…It has been observed that electrochemical techniques represent low cost and high selectivity along with the fruitless recovery of treated metals for a recycled, high volume of sludge formation [9,14]. Likewise, the ion exchange and membrane filtration processes are restricted due to their selectivity, high operational cost and maintenance issues [20]. However, the adsorption process, by all accounts, has shown unrivaled outcomes due to its minimal effort, high effectiveness and selectivity [21].…”