REVERSE OSMOTIC SEPARATION OF SODIUM-CHLORIDE AND COBALT(II) CHLORIDE THROUGH MEMBRANES PREPARED FROM SCHIFF-BASES OF POLYALLYLAMINE

Crosslinked membranes from Schiff base derivatives of polyallylamine were prepared with 2-pyridinecarboxaldehyde (P) and with P followed by salicylaldehyde, and used for the reverse osmotic separation between sodium chloride (NaCl) and cobalt(II) chloride (CoCl), The membranes whose rejection (R) was high against CoCl2 and low against NaCl at each single feed supply showed a reduced difference in R in the case of a mixed solute feed due to Donnan exclusion by fixed charges in the CoCl2-complexed membrane. An approximate calculation of the complexed CoCl2 revealed that a very small portion of Schiff base groups took part in the complexation. Composite membranes on a cellulosic sheet solved the problem of an extreme reduction of the membrane strength after complexation, enabling continuous and repeated use. Some transport parameters were determined. Since they indicated a semipermeable character for CoCl2, multistage runs of a single membrane or low pressure runs of a more porous composite membrane were suggested for the effective separation of NaCl and CoCl2. © 1990, Taylor & Francis Group, LLC. All rights reserved.