Patent ID: 7498012

Claim:
A desulfurization process of a pastel and/or grids contained in lead accumulators characterized in that it comprises a desulfurization in two phases, wherein, in the first phase the lead sulfate of the pastel is put in contact with Na 2 CO 3 in solution to react according to the following reaction: 3 PbSO 4 +3 Na 2 CO 3 +H 2 O→Pb 3 (CO 3 ) 2 (OH) 2 +3 Na 2 SO 4 +CO 2 (I) 2 Pb 3 (CO 3 ) 2 (OH) 2 +2Na 2 CO 3 →3 NaPb 2 (CO 3 ) 2 OH +NaOH (II) providing a dispersion comprising a carbonated pastel based on basic lead carbonates and thereafter decanting the dispersion obtained from the first phase to recover a carbonated pastel based on basic lead carbonates and a basic solution containing Na 2 CO 3 which is neutralized with a solution based on H 2 SO 4 to produce CO 2 according to the reaction: Na 2 CO 3 +H 2 SO 4 →Na 2 SO 4 +CO 2 +H 2 O (V) which, in a second phase, is reacted with CO 2 according to the following reaction: Pb 3 (CO 3 ) 2 (OH) 2 +CO 2 →3 PbCO 3 +H 2 O (VII) NaPb 2 (CO 3 ) 2 OH+CO 2 →2 PbCO 3 +NaHCO 3 (VIII) to give a dispersion comprising a desulfurized pastel based on PbCO 3 .