Process for the high yield recovery of lead from spent lead-acid batteries with reduced associated production of slag and gaseous emissions

Abstract

Process for desulphating a solid mixture and/or aggregate resulting from the breaking up of lead-acid batteries, comprising electrode slime containing lead compounds belonging to the group comprising oxides, oxidated compounds and sulphates, through contact with an aqueous solution of sodium carbonate and a substance dissolving lanarkite in which the said solid residues containing lead compounds are suspended, in which the solid phase of the suspension is subjected to a chemical reaction whose action is assisted by brushing, shear and compression forces exerted by brushing or scraping and compressing mechanical means, thus achieving almost total desulphatation.

1 . Process for desulphating a solid mixture resulting from the breaking up of lead-acid batteries, comprising electrode slime residues containing lead compounds belonging to the groups comprising oxides, oxysulpahtes (lanarkite) and sulphates, characterized in that said lead compounds are put in contact with the aqueous solution containing in contact with a aqueous solution containing alkali carbonate (sodium or potassium carbonate) in the stoichiometeric quantity sufficient for sulphate concentrations present in the electrode slime, plus an excess of between 0.01% and 10%, and alkali (sodium, potassium) hydroxides which dissolve lanarkite in a molar ration of carbonate to alkali of between 1 and 2.75, in which the said lead compounds are suspended, the solid phase of the suspension of being subjected to the fragmenting action of shear and compression forces exerted by brushing, scraping and compressing mechanical means.  
     
     
         2 . Desulphating process according to  claim 1 , characterized in that the carbonate/solvent molar ration is less than 1.  
     
     
         3 . Desulphating process according to  claim 1 , characterized in that the ratio by weight between water and the suspended solid phase lies between 0.6 and 5.  
     
     
         4 . Desulphating process according to  claim 1 , characterized in that the sodium carbonate in the said solution is in excess with respect to the stoichiometeric quantity necessary for the quantity of sulphate present up to a maximum of 10 percentage points and the carbonate/alkali molar ratio may be between 1 and 2.75.  
     
     
         5 . Desulphatiang process according to  claim 1 , characterized in that the contact time necessary for almost total conversion of the lead sulphate to lead carbonate is between 30 and 90 minutes.  
     
     
         6 . Desulphating process according to  claim 1 , characterized in that it takes place at a temperature between ambient temperature and the boiling point of the solution.  
     
     
         7 . Process according to  claim 6 , characterized in that it takes place at a temperature of between 60 and 100° C.  
     
     
         8 . Pyrometallurgical process for the recovery of lead from lead-acid battery electrode slime residues without the use of iron in the charge, characterized in that the said residues are first desulphated in accordance with the procedure according to  claim 1  until they are substantially free of lead sulphate.  
     
     
         9 . Desulphating process according to  claim 2 , characterized in that it takes place at a temperature between ambient temperature and the boiling point of the solution.  
     
     
         10 . Desulphating process according to  claim 3 , characterized in that it takes place at a temperature between ambient temperature and the boiling point of the solution.  
     
     
         11 . Desulphating process according to  claim 4 , characterized in that it takes place at a temperature between ambient temperature and the boiling point of the solution.  
     
     
         12 . Desulphating process according to  claim 5 , characterized in that it takes place at a temperature between ambient temperature and the boiling point of the solution.