RETENTION OF COPPER(II)-EDTA CHELATES FROM DILUTE AQUEOUS-SOLUTIONS BY A POLYELECTROLYTE-ENHANCED ULTRAFILTRATION PROCESS

The retention behavior of copper(II)-ethylenediaminetetraacetic acid ( EDTA) chelates in dilute aqueous solutions ([Cu2+] = 0.5-4 mM) by ultr afiltration was studied with the help of a basic polyelectrolyte, poly ethylenimine (PEI). The regenerated cellulose Amicon YM10 and YM30 wer e used as ultrafilters. Experiments were performed in a stirred batch cell as a function of aqueous pH (2-10), the concentration ratios of E DTA to copper ions (0.5-4) and of PEI to copper ions (2.5-20), and the applied pressure (0.68-3.40 atm). The best conditions for rejection c oefficient greater than 97% equivalent to 7 ppm copper chelates were o btained. The effect of inorganic salts such as NaCl, CaCl2, and Na2SO4 on the retention was also examined. In addition, the membrane fouling during ultrafiltration was analyzed by modified fouling index. The re generation method of PEI from the retentate is finally discussed.