Recovery of metal ions from electroplating rinse solutions using the Donnan dialysis technique

Electroplating rinse solutions contain considerable amounts of multivalent valuable or toxic metal ions. The attempt to recover them was made using the Donnan dialysis (DD) technique, applying a cation-exchange polymer membrane. Laboratory experiments dealing with processing two different solutions containing Zn(ll) [A], or Zn(II), Cu(II), Ni (II), Cr(III) and Fe(III) [B] were carried out. The results demonstrated DD to be efficient for recovering Zn(II) (soln.A) and other multivalent metals (soln.B) in the sequence Ni, Cu>Fe>Zn>Cr. Recovery factors amount to 80-90% and 74-94% for A and B solutions, respectively. The optimum concentration of sulfuric acid in the strip solution ranges from 0.25 to 0.5 M.