STC proposes a chemical process at low temperatures for the purification of lead oxide from lead battery recycling, produced with the hydrometallurgical process to convert lead paste into lead oxide, which allows to purify the oxide from a possible presence of other metals.
The process for the production of ultrapure lead oxide from lead battery recycling, patent protected in Europe, is an environment friendly and cost saving closed loop operation.
The raw oxide undergoes the following treatments:
- Leaching of the raw oxide with an aqueous solution of acetic acid followed by filtering to separate a solid residue, containing: lead sulphate (PbSO4), antimony, cadmium, copper etc. and probably also some lead dioxide, from a lead acetate solution;
- Purification of the obtained solution through addition of reagents which make it possible to remove possible dissolved impurities from the solution;
- Precipitation of the lead acetate in solution by means of an alkaline or an acid compound in order to get a precipitate of lead hydroxide;
- Filtering or sedimentation of the lead hydroxide obtained, followed by washing with demineralized water;
- Drying and calcination of lead oxide in order to get high purity hydrate or lead oxide depending on the drying temperature;
- Acidification of the acetate solution left after the filtration through a sulphuric acid and precipitation of the sodium sulphate by means of crystallization with recovery of the acetic acid solution as distilled to be reused at the beginning of the production cycle.
This process of lead battery recycling can be self-sustaining when the complete recycling of the reactants is included. In this case no waste is generated. The process with complete recycling of the reactants deals with most environmental and pollution issues generally connected to the processes for lead recovery from battery paste. The ultrapure lead oxide from lead battery recycling can be used in the production for new lead/acid batteries.