Investigations on obtaining cathodic cobalt in a diaphragm type electrolyser

The investigations on cobalt electrolysis from cobalt chloride solutions while using diaphragm electrolyser have proved that: 1) Electrodeposition of cobalt should be carried out from solutions, where the pH value ranges from 5.1 to 5.3; the cathode cobalt obtained under those conditions was solid metal, bright and glossy; the current efficiency of the cathode process was 98%. 2) Three stages can be distinguished in the course of electrolytic cobalt deposition from CoCl2 solutions. Stage I – slight changes in the pH value of the catholyte solutions, duration this stage depends an cobalt concentration in the solution. Cobalt obtained during this stage adheres very well to the cathode, its survace is smooth and glossy. Stage II – rapid decrease of pH in the catholyte and first hydrogen bubbles appar (pH≅3.0). Stage III – the electrolysis proceeds with a continuous but small decrease of the catholyte pH value; the cathode deposit begins to come off the ground, it is dark and full of pits;. the current efficiency of the process drops to about 90%. 3) Electrolyser modification by introducing buffer compartments that separate catholite from the anolyte makes possible to extend the stage I of electrolysis which is the most favourable stage in the whole process of cobalt deposition.