Study of a pilot plant for the recovery of metals from spent alkaline and zinc-carbon batteries with biological sulphuric acid and polithionates production

Abstract

The recovery of Zn and Mn from spent alkaline and Zn-C batteries with a biohydro-metallurgycal process was studied in a pilot plant that consists in an air lift bio-reactor with a sulfur packed bed where Acidithiobacillus thiooxidans produces an acid-reducing medium; a leaching reactor where the acid-reducing medium is mixed with the battery powder and a recovery reactor where metals are recovered from the leaching liquor by electroly-sis. Results shows that with a 350 mM in proton me-dium produced in 12 days by Acidithiobacillus thiooxidans in the bio-reactor, an extraction of the 100% of Zn and 67% of the Mn present in the bat-tery powder was reached. The presence of polithionates in the medium produced in the bio-reactor allows the dissolution of the manganese. The solid remaining after bioleaching is a manganese oxide. The electrolysis of the leaching liquor pro-duced a cathodic deposit of metallic Zn and an an-odic deposit of a high surphase manganese oxide in one step at room temperature.