Processes Based on Aqueous Electrolysis

PROCESSES BASED ON AQUEOUS ELECTROLYSIS Chloride systems 

It is also possible to electrolyse a solution containing iron in the ferrous state in a compartmented-diaphragm cell. Ferrous iron will not interfere with the cathode reactions but will be oxidised to ferric iron in the anode compartment. To achieve this, feed solution enters the cathode compartment and electrolyte passes through the diaphragm, constructed of an inert fabric, to the anode compartment and exits the cell. The anolyte can then be reused for leaching. Any escape or return of ferric iron to the cathode compartment will result in its reduction to ferrous iron in preference to lead deposition, thus reducing process current efficiency for lead recovery. 

In the case where leach solution is used for cell feed, purification of the solution by canentation with lead powder is necessary, as well as the treatment of a bleed to prevent the build-up of other impurities such as zinc, calcium and magnesium. It is also important that the iron present in feed solution is fully in the ferrous state to maintain high current efficiency by avoiding the reduction of ferric iron at the cathode. To ensure this, it is preferable to have a two-stage counter-current leach in which excess sulfides are in contact with the final leach solution. Some excess ferrous iron (10 to 15 g/L) should also be maintained in the anolyte to impede the formation of chlorine at the anode. 

4 - Aqueous chloride electrolysis tor lead (PLACID process). 

5 - Aqueous ferric chloride leaching and electrolysis (Minemet process). 

---