GOLD ELECTROLYTIC REFINING Working principles Electrolysis is a technological process that utilises the electric energy generated from a current rectifier and from the technical features of acid solution. The metal to be deposited (in this case Au) is melted by a liquid solution called gold chloride. The metal to be refined is generally composed of almost pure gold (min. 995,0‰), previously melted and poured in a special mould called ANODE which will be placed to the positive pole. The cathode, a very thin plate of pure gold (999,9‰) will be placed to the negative pole. By means of a proper electromotive force and for the electrolytic bath characteristics , the metal anodes will gradually dissolve; at the same time, through the natural pole attraction between electrodes, gold migrates towards the cathode under metallic sponge form, in the plunged cathode surface. Once the operation is over, the initial cathode and the total gold sponge deposited , are properly washed , melted and prepared for the following working phases. Being a selective process for noble metals, when the operation ends, the cathode will carry only an elevated fineness gold deposit: 999,9‰. Productivity is to be considered in 24 h. cycle and taking into consideration the number of anodes used in the cells, following from the morning these operations: 1 – Cathodes recovery / washing and melting 2 – Recovery of anodes pieces / washing 3 – Melting of new anodes 4 – Bath maintenance (acidity and gold analysis) 5 – Bath filtering / parameter correction 6 – New cathodes positioning / pre-heating 7 - New anodes positioning 8 – Initial current setting 9 – Gradual current increasing up to proper parameter achievement 10 – Control of baths and adding systems levels Why refining by electrolytic system? This refining method is certainly slower than Aqua Regia system, but this is paid back by the higher gold purity recovered: 999,9‰. The user of this system is an already refiner by Aqua Regia (minimum guarantee 999,5‰) who assigns part of the worked out product to the electrolytic system refining when the maximum purity is requested. Example: out coming from Aqua Regia plant 20 Kg, fineness 999,7‰. From this point 2 kg of pre-refined metal is addressed to electrolytic system to obtain the maximum fineness gold.