Lead recovery from a typical Brazilian sludge of exhausted lead-acid batteries using an electrohydrometallurgical process

Lead recovery from the nonmetallic portion of exhausted lead-acid batteries, also called sludge, was investigated using an electrohydrometallurgical process. Among 13 aqueous solutions studied in solubility tests, only the following three were chosen for the whole process (leaching and electrowinning steps): tetrafluoroboric acid (200 g/L), glycerol (92 g/L)+sodium hydroxide (120 g/L) and sodium potassium tartrate (150 g/L)+sodium hydroxide (150 g/L). The tetrafluoroboric acid showed an attractive performance as leaching electrolyte due to its low cost and reasonable leaching strength. In the electrowinning process using the solution obtained from the leaching of a desulfated sludge with this acidic electrolyte, compact, adherent and highly pure lead deposits were produced at 250 A/m2. Scanning electron micrographs (SEM) of lead deposits obtained at different current densities in the range of 250–500 A/m2 revealed a marked influence of the current density on the deposit morphology.