Removal of copper(II) chelates of EDTA and NTA from dilate aqueous solutions by membrane filtration

The removal of Cu(II) chelates of ethylenediaminetetraacetic acid (EDTA) and nitrilotriacetic acid (NTA) from aqueous solutions was studied by batch ultrafiltration (UF) with the help of poly(ethylenimine) (PEI). The Amicon regenerated cellulose YM10 and YM30 were used as ultrafilters. Experiments were performed as a function of aqueous pH, the concentration ratios of chelating agent to Cu(II) ions (alpha) and of PEI to Cu(II) ions (beta), and the applied pressure (Delta P). In general, the removal of Cu-EDTA chelates was more effective compared to that of Cu-NTA chelates. Under the conditions tested (pH 4, Delta P = 2.04 atm, [Cu2+] < 4 mM), the removal efficiency was higher than 97% for Cu-EDTA chelates when alpha > 0.5 and beta > 10 and higher than 96% for Cu-NTA chelates when alpha > 0.5 and beta > 20. The effect of the presence of inorganic salts on the removal was also investigated. Finally, the membrane fouling during UF was analyzed by modified fouling index, and the regeneration of PEI was examined.