Purification of aqueous solutions of metal ions by ultrafiltration

This study gathers experimental results that illustrate the efficiency of ultrafiltration in the purification of aqueous solutions of metal ions beforehand complexed on water-soluble macromolecular substrate. For this purpose, a commercial polyethersulfone ultrafiltration membrane is employed in a magnetic stirred cell operating in a batch mode. The metal ions Cu2+, Co2+, Ni2+, Zn2+, Fe3+ and Ag+ are removed from synthetic aqueous solutions which contain poly(vinyl alcohol) used as macromolecular complexing agent. It is, primarily, observed that, except silver ions, all the other studied metal ions are removed from monoionic solutions with a rejection higher than 97%. Moreover, the possibility to separate the cupric ions from the other metal ions is studied and the removal of silver ions from a diionic solution containing cupric and silver ions is achieved. The studied parameters are the effect of the pressure, the molecular weight of the sequestering agent and the nature of the ionic species in solution on the permeate flux through the ultrafilter and the rejection of the metal species by it.