Chronopotentiometry of an anion-exchange membrane for treating a synthesized free-cyanide effluent from brass electrodeposition with EDTA as chelating agent

The promising substitution of cyanide by EDTA as chelating agent in brass electrodeposition has been evaluated by many researchers in the last few years. This is very interesting for treating the effluent generated, since the presence of EDTA facilitates the recovery of the metals using electrodialysis, for example. Hence, using chronopotentiometry, our aim was to investigate the transport properties of the chelates involved in the potential treatment by electrodialysis of the effluent generated in the free-cyanide brass electrodeposition. We assessed the limiting current density, ohmic resistance, plateau length, concentration polarization and the undesirable precipitate formation in function of the solution pH, Cu2+/Zn2+ proportion and EDTA/Cu2+ molar ratio using the anionic HDX200 membrane. The pH solution showed a strong relation with all the properties and under higher pH, precipitate formation by the curves behavior was verified. Besides, the precipitate formation was also observed for the lower proportion of Cu2+, while no unexpected behavior was verified for Cu2+ concentrations >= Zn2+. Finally, the EDTA concentration altered only the limiting current density, since similar typical chronopotentiograms and current-voltage curves were obtained. It was found that the better conditions of the effluent to be treated may be pH 9/10, Cu2+ proportion = 50% and EDTA/Cu2+ = 2.5.