Purification of a diluted nickel solution containing nickel by a process combining ion exchange and electrodialysis

The removal of nickel ions from diluted solution using some ion-exchange resins (Dowex MSC-1, Purolite C 100E, KU 2-8 and Dowex HCR-S) was studied. The purification process involved the use of an electrodialysis-type cell in which the centre compartment was filled with a packed bed of ion-exchanger particles. The Dowex HCR-S resin was shown to be the most suitable material for use in electrodeionization processes. The current efficiency under constant rate of nickel transport to the catholyte reached 14%. The energy consumption, which is needed for removal of 0.35 mol Ni (II) from 1 m(3) solution containing 1 mol NiSO4, was estimated as 208 Wh. The apparent diffusion coefficients of Ni(H) ions in the ion exchangers were determined with the electromigration method. These values increased with decrease of the effluent pH and reached 1.30(.)10(-12) (Dowex MSC-1 ), 1.36(.)10(-12) (Purolite C 100E), 2.69(.)10(-12) (KU 2-8), and 4.07(.)10(-12) (Dowex HCR-S) m(2) s(-1) at pH 2.3 -2.5. The largest magnitude of the nickel diffusion coefficient was obtained for the Dowex HCR-S resin, which contains the maximum quantity of functional groups per volume unit. It was found that the mobility of sorbed ions determines the efficiency of the purification process.