Green separation of copper and zinc using triblock copolymer aqueous two-phase systems

• A green and low cost technique for metal separation was discovered.
• Aqueous two-phase system (ATPS) is predominantly composed by water.
• ATPS is an efficient substitute for liquid-liquid extraction using organic solvent.
• Excellent separation factor for Cu and Zn was obtained.

The separation of copper and zinc was studied using aqueous two-phase systems (ATPSs) formed by triblock copolymers (L64), electrolyte (MgSO4, Li2SO4 or Na2C4H4O6) and water in the presence of 1-(2-pyridylazo)-2-naphthol (PAN) as an extractor. The separation behavior of the metals is affected by the quantity of extractor added, the pH of the system, the nature of the ATPS electrolyte and the system composition. The maximum separation (SCu,Zn = 204) of Cu and Zn was obtained with the L64 + Na2C4H4O6 ATPS at pH 3.0, a tie-line length of 41.28% (m/m) and a PAN/metal molar ratio of 3.0. For this ATPS system and at the same thermodynamic condition, the copper stripping percentage reached a maximum value (%S = 83.3%) using H2SO4 0.076 mol kg−1.