ELECTROCHEMICAL RECOVERY OF NICKEL FROM ELECTROPLATING EFFLUENTS BY AN 'ELECTRO-ACTIVE MIXED BED RESIN CATHODE'

摘要

In this paper results are presented concerning the direct electrolytic recovery of nickel from plating rinse water by using a combination of a high surface to volume ratio cathode material (fibre structure) and an ion exchange resin in contact with the fibre structure of the metal cathode and dispersed in the cathode compartment. Two types of resins have been tested on their capacity and kinetics of nickel uptake from an industrial bright nickel plating effluent containing ～ 2 g/l nickel. For an applied feed rate of 6.5 bed volumes per hour IRC 748 (Rohm & Haas) showed the a lower capacity compared to TP 207 (Bayer) but a sharper cut off profile. Elution curves of the loaded resins with 5 % sulphuric acid also yielded a sharper curve with IRC 748. As cathode material both fibrous titanium (525 g/m~2, O 35 μm) and stainless steel (300 g/m~2, O 30 μm) have been tested. It is shown that, by the introduction of IRC 748 near a fibrous titanium electrode and operating the cell at 10 A/m~2 a recovery rate of 85% can be obtained after saturation of the resin with nickel. A current efficiency of 58% was obtained when the pH of the solution was kept constant at 5.5. Although on both electrodes an adherent metallic nickel layer was obtained, it was found that the stainless steel electrode was very sensible for the generation of unwanted nickel precipitates when NaOH solution was introduced in the cell to regulate solution pH.