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Sodium Chloride Removal from Urine via Electrodialysis for Use in Advanced Life Support.  V. M. Aponte, N. E. Gordils and G. Colуn.  Dept of Chemical Engineering, Univ of Puerto Rico, Mayagьez.

   A six-compartment electrodialysis cell using univalent ion selective membranes was proposed to remove sodium chloride from human urine.  Limiting current density (i_lim) data were obtained at four fluid velocities ranging from 0.015 to 0.083 m/s, and four urine concentrations ranging from 3200 to 12800 ppm, based on chloride salts concentration.  The i_lim was found to be a power function of fluid velocity and Cl^- salts concentration as correlated by the model i_lim/C^*=4105 U^0.90. Ion chromatography revealed that the highest sodium chloride percentage for continuous once-through mode of operation was of 91.0 % achieved at the most diluted solution (U=0.039 m/s and i=57 A/m²).  For batch recirculation, the highest removal, 98.5 %, was achieved at a potential of 9.0 volts and U=0.083 m/s. An average current efficiency of 50 % indicates that half of the applied current was used in sodium chloride transport.

     (Supported by NASA:  NAG10-0257.)