STC has developed a new technology for the recycling of lead batteries. This process allows the simultaneous production of lead dioxide PbO and metallic lead by means of an electrochemical process. The raw material for the present process comes from the hydrometallurgical process that converts lead paste in lead oxide realized by STC.
The process for the contemporary production of metallic lead and lead oxide in recycling of lead batteries is extremely convenient operating at low temperatures and without production of slag and emissions.
The recycling of lead batteries with the STC process starts with the leaching of the calcinated oxide through fluoboric acid HBF4. Fluoboric acid has been widely used in hydro-metallurgy and electro-winning of lead and is therefore a reliable reagent for electrolysis operations. The solution of Lead fluoroborate Pb(BF4)2, obtained from leaching, is purified through the addition of some reagents which make it possible to get rid of possible dissolved impurities from the solution.
At the end of the purification process the solution is filtered and sent to an electrolytic cell where lead sediments on the cathodes and lead dioxide on the anodes. From the electrochemical reaction fluoboric acid is regenerated.
The Lead dioxide can be calcinated at 600°C and subsequently partially reduced with hydrogen to ultrapure lead and lead oxide for the production of new batteries. The cathodes of metallic lead are melted and can be casted in ingots of electrolytic lead.