Abstract
The aim of this study is the thermal recovery of manganese and zinc from a mixture of zinc-carbon and alkaline spent batteries containing 40.9% of Mn and 30.1% of Zn after a preliminary physical treatment. Separation of the metals is carried out on the basis of their different phase change temperatures, the boiling point of zinc being 906°C and 1564°C that of Mn3O4, the main Mn-bearing phase in the mixture. After wet comminution and sieving to remove the anodic collectors and most of the chlorides contained in the mixture, chemical and X-Ray Powder Diffraction (XRPD) analyses were performed. The mixture was heated in CO2 atmosphere and the temperature raised, thus permitting the zinc oxide to be reduced to metallic zinc by the carbon present in the original mixture. Other tests were carried out by addition to the mixture of activated charcoal (95% C) or of the automotive shredder residue (fluff) containing 45% C.A zinc product was obtained suitable, after refining, for the production of new batteries. The treatment residue consisted of manganese and iron oxides that could be used to produce manganese-iron alloys. From these results, an integrated process for the recovery of the two metals was proposed.
Highlights
Manganese and zinc are important metals in many fields
The results of this study demonstrate that manganese and zinc can be recovered from zinccarbon and alkaline spent batteries
According to the proposed thermal process, a recovery of 90% zinc can be obtained at the temperature of 1200°C by using carbon dioxide and carbon addition to the paste of spent batteries
Summary
Iron is contained in the end caps, in the alkaline battery steel cans and, in some cases, in the steel outer jackets of the zinc-carbon batteries, while copper and zinc are present in the alkaline battery brass negative current collectors. These components could be removed and recycled from spent batteries, while an additional separation process is required for the recovery of manganese and zinc, since most of these metals are found in the paste inside the battery. Both methodologies are generally preceded by physical methods of separation to improve the efficiency of the successive recovery steps
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