Simultaneous recovery and separation of Zn2+ and Cu2+ in hybrid membrane systems

Transport and separation properties of a double multimembrane hybrid system (d-MHS) composed of: stripping solution (1) | MHS(1) | feed solution | MHS(2) | stripping solution (2) have been studied. In the system each MHS comprises an agitated bulk liquid membrane (BLM) placed between two cation-exchange polymer membranes (CEM). The simultaneous recovery and separation of Zn2+ and Cu2+ from a binary or multicomponent (Zn2+, Cu2+, Ca2+, Mg2+, K+, Na+) solution has been performed by using two parallel BLMs selectively transporting one of the two target cations. The d-MHS exploiting 5-nonylsalicyl-aldoxime (Acorga P-50, Cu2+ selective) and di-(2-ethylhexyl) phosphoric acid (D2EHPA, Zn2+ selective) in particular BLMs allows the simultaneous separation and up-hill transport of the two cations. A new d-MHS system integrated with the Donnan dialysis process (DD-d-MHS) has also been constructed in order to preconcentrate cations before their separation through the two MHS modules. The application of DD-d-MHS to remove Zn2+ and Cu2+ from contaminated (0.001 mol/dm3 Zn(NO3)2 and Cu(NO3)2) tap water (model feed for electroplating rinse solution) results in approx 86-88% recovery of both cations from the feed and their active concentration with the following selectivity coefficients: βMZn = 170 and βMCu = 530.