Characteristics of Reverse Osmosis Membranes Prepared from Schiff Bases of Polyallylamine in Aprotic Solvents and Separation of Inorganic and Organic Solutes through the Membranes

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Abstract
Four different aprotic solvents, N, N−dimethylformamide, dimethylsulfoxide (DMSO), N, N−dimethylacetamide, and N−methyl-2-pyrrolidinone, were used for the preparation of crosslinked membranes of polyallylamine Schiff base derived from 2-pyridinecarboxaldehyde and salicylaldehyde. The membrane from DMSO showed performances quite different from those of the membranes from three other solvents. This was attributable to the reduced solvating power of DMSO leading to a porous membrane, from the comparison of viscosity, turbidity, and surface tension of the polymer solutions, the swelling degree of the membranes, and SEM observation. Cobalt(II) salt-complexed membranes were very hydrophilic and water permeated preferentially from aqueous solutions of organic substances. The separation factor strongly depended on the molecular size of the solute. Cobalt(II) chloride had a higher complex stability and hydrophilicity, and it showed a better performance than cobalt(II) sulfate.