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Abstract:
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Partially disulfonated poly (arylene ether sulfone ) (BPS ) membranes have shown great promise as robust , chlorine tolerant alternatives to the current polyamide materials as reverse osmosis desalination membranes for water purification . The random copolymers are synthesized by direct polymerization of a disulfonated monomer (3 ,3’ -disulfonato -4 ,4’ -dichlorodiphenyl sulfone (SDCDPS ) ) and other monomers (4 ,4’ -dichlorodiphenyl sulfone (DCDPS ) and 4 ,4’ -biphenol (BP ) ) . The sulfonation of the materials adds necessary hydrophilic character and adjusting the percent sulfonation of the material changes the water and salt uptake of the material . Additionally , sulfonation causes the membranes to be charged , making them ion exchangers in which anions are partially excluded from the membrane , thus affecting the partitioning of salt in the membrane . The amount of sodium chloride present in the membrane after equilibration with external soaking solutions of varying concentrations of sodium chloride was measured by measuring the amount of individual ions , i .e . , the sodium cation and chloride anion , separately . One area in which this work is unique is that it sought to measure the concentrations of the ions independently of one another . The analysis of sodium and chloride has shown the concentration of sodium in the membrane to be significantly greater than that of chloride , where the uptake of chloride is the limiting factor in the uptake of sodium chloride . The trends in the concentrations as well as in the partition coefficients of the ions are consistent with Donnan Exclusion . |