Preparation of and optimal module housings for hollow fibre membrane ion exchangers

Macroporous polyamide 6 hollow fibres can be polymer coated by a three-step procedure: first, reaction of the amino end groups with a bifunctional, double-bond-containing reagent; second, block polymerization with different monomers; and third, polymer analogue reactions with amines or sulphite salts to produce ion exchanger groups. The densities of double bonds are dependent on the amino densities and are in the range of 20-30 mumol/g polyamide 6. The ion exchanger fibres were packed in different types of module housings to get an optimal separation unit. The best housing seems to be a so-called single-dead-end arrangement of fibres. Three types of ion exchanger hollow fibres have been produced: a weak and a strong anion exchanger and a strong cation exchanger. The dynamic protein-binding capacities are in the range of 40 mg/ml membrane. Using these membrane modules, it is possible to separate proteins in the same way as with particle-based ion exchangers. Fast protein separations with low pressure drop are possible.