Dialysis

1
Dialysis

• Diffusional process
• Separation is based primarily on solute size
• Partition
• Diffusion
• Degree to which the membrane restricts transport
  of molecules usually increases with solute size
• Applications
• Removal of acid or alkali from products
• Removal of alcohol from beer (to make alcohol
  free beer)
• Removal of salts and low molecular weight
  compounds from solutions of macromolecules
• Concentration of macromolecules
• Dialysis provides a tool for controlling the
  chemical species within a reactor
• Purification of biotechnological products
• Haemodialysis

2
Hollow fibre dialyser
Feed
Product
Dialyzing solution (sweep stream)
Dialysate
Dialysate
Dialyzing solution (sweep stream)
Product
Feed
C1
C1
Co-current flow
Counter-current flow
C3
C4
C4
C3
C2
C2
3
Co-current and counter-current dialysis
Log-mean concentration difference
Co-current
Counter-current
Feed side
Feed side
Conc.
Conc.
Dialysate
Dialysate
Length of membrane
Length of membrane