Spent lead–acid batteries have become the primary raw material for global lead production. In the current lead refining process, the tin oxidizes to slag, making its recovery problematic and expensive. This paper aims to present an innovative method for the fire refining of lead, which enables the retention of tin contained in lead from recycled lead–acid batteries. The proposed method uses aluminium scrap to remove impurities from the lead, virtually leaving all of the tin in it. The results of the conducted experiments indicate the high efficiency of the proposed method, which obtained a pure Pb-Sn alloy. This alloy is an ideal base material for the production of battery grids. This research was carried out on an industrial scale, which confirms the possibility of facile implementation of the method in almost every lead–acid battery recycling plant in the world.

Lead grid from spent lead-acid batteries contains significant amounts of tin and antimony. In classical pyro-refining processes of lead, tin oxidizes and is transferred to dross, making its recovery problematic and expensive. This paper presents an innovative method of pyro-refining lead using metallic aluminum and calcium to purify the lead from contaminants while retaining a higher amount of tin than in the traditional process. The changes in the chemical composition of an impure lead alloy containing tin, under the influence of refining by adding Al and/or Ca, are discussed based on laboratory-scale studies. Microanalysis of the metallic dross formed during the process was conducted. Analyses of the metallic dross microstructures showed that lead impurities, such as Sb, As, Cu, Se, and Te, tend to accumulate in areas containing Al or Ca. The amount and form of dross produced in industrial practice indicate that its removal would be challenging. Therefore, in the second part of the study, the metallic dross was subjected to a reduction process, and the resulting products were analyzed for their chemical and phase composition. The analyses indicate that the degree of impurities return to the lead during reduction varied significantly depending on the method used.

The purpose of this study was to investigate the processes occurring during the refining of lead with aluminum, by analyzing and studying ternary Pb-(M)-Al systems, where M is one of the following metals: Sb, As, Se, Cu or Ni, which are the main contaminants of secondary lead from recycling waste lead-acid batteries. The Pb-Sb-Ca system, crucial for removing antimony while retaining tin, was also analyzed. The research included analysis of 2- and 3-component phase systems simulated, process kinetics under laboratory conditions for pure ternary systems, and chemical and phase composition analysis. Phase analysis showed the presence of permanent aluminum compounds such as AlSb, AlAs, Al₂Se₃, Al₃Ni and phases with copper in the dross. In addition to the direct association of aluminum with a given contaminant, aluminum oxides such as Al_0.5Sb_0.5O₂ and AlAsO₄ as well as calcium oxide with antimony Ca₄Sb₂O₇ were also found in the dross. On the basis of the tests carried out, 680 °C was considered the optimal temperature for starting the refining process, with the amount of aluminum that was approx. The research provides new scientific data toward more efficient secondary lead refining technologies relevant to recycling waste lead-acid batteries and producing lead-tin alloys for the battery industry. Graphical Abstract

Impurities in lead alloys affect the production yield and grid quality of lead-acid batteries. In addition to contamination limits, battery manufacturers often specify the maximum level of dross that can be produced when melting a given alloy. This study presents, for the first time, an example of a method for determining the percentage of dross formed after melting an alloy. In addition, the effect of three different lead pyrorefining methods—traditional refining, traditional refining with the double addition of NaOH and NaNO₃ and an alternative method using metallic aluminum—on the percentage of dross produced during the melting of the PbSnCa alloy was evaluated. Industrial-scale experiments have revealed significant differences in the amount of melt dross formed, confirming the influence of the refining method on this parameter. The aluminum refining method gave a lower dross content than the traditional approach and showed the highest process stability. Microstructural and phase analysis indicated that the resulting dross consisted mainly of metallic lead mixed with oxide phases. The results highlight the potential of lead refining using aluminum and provide valuable insights into optimizing lead recycling practices, as well as being a valuable knowledge base for lead-acid battery manufacturers.