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

Abstract

The recovery of Zn and Mn from spent alkaline and Zn-C batteries with a biohydrometallurgycal process was studied in a pilot plant that consists of an air-lift bioreactor with a sulphur 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 electrolysis. Results show that with acid medium (350 mM[H+]) produced in 12 days by Acidithiobacillus thiooxidans in the bioreactor, an extraction of 100% of Zn and 67% of the Mn present in the battery powder was reached. The presence of polythionates in the medium produced in the bioreactor allows the dissolution of the manganese. The solid remaining after bioleaching is a manganese oxide. The electrolysis of the leaching liquor produced a cathodic deposit of metallic Zn and an anodic deposit of a manganese oxide in one step at room temperature.