Whey desalination using polymer and inorganic membranes: Operation conditions

Electrodialytic desalination of cheese whey was carried out using a pair of
polymer cation exchange (Nafion 117) and inorganic membranes. The ceramic
separator was modified with nanocomposite containing hydrated zirconium
dioxide and basic bismuth nitrate. This amphoteric filler provides anion
exchange ability of the composite membrane. This property is realized when at
least one side of the membrane is in contact with an acidic solution. Ion
transport through the membranes was shown to be determined by current, whey
acidity, and also by composition of the solution in the concentration
compartment of the electrochemical cell. It was shown that whey desalination
occurred under overlimiting current. Acidification of whey and decrease of
the acid content in the concentrate suppress ion transport. The
electrodialysis of whey and nanofiltration permeate allowed removal of up to
80% of the mineral components in 5 h and 40 min, respectively. Preliminary
ozonation of the permeate increased the rate of desalination.