Recycling of Spent Lead-Acid Battery for Lead Extraction with Sulfur Conservation
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https://doi.org/10.1007/s11837-019-03885-y Ó 2019 The Minerals, Metals & Materials Society
THERMODYNAMIC MODELING OF SUSTAINABLE NON-FERROUS METALS PRODUCTION
Recycling of Spent Lead-Acid Battery for Lead Extraction with Sulfur Conservation YUN LI,1,2 SHENGHAI YANG,1 PEKKA TASKINEN,2 JING HE,1 YONGMING CHEN,1,3 CHAOBO TANG,1,4 and ARI JOKILAAKSO1,2,5 1.—School of Metallurgy and Environment, Central South University, Changsha 410083, China. 2.—Department of Chemical and Metallurgical Engineering, Aalto University, 02150 Espoo, Finland. 3.—e-mail: [email protected]. 4.—e-mail: [email protected]. 5.—e-mail: [email protected]
This study proposed a cleaner pyrometallurgical lead-acid battery (LAB) recycling method for lead extraction and sulfur conservation without an excessive amount of SO2 generation. A reducing atmosphere was introduced to the lead paste recycling system to selectively reduce PbSO4 to PbS. At the same time, PbO and PbO2 components contained in the lead paste were also reduced to metallic Pb. Then, the intermediate PbS further reacted with a sulfur-fixing agent, typically Fe3O4, to generate PbO and FeS. Sulfur was transformed from PbSO4 to PbS and finally conserved as FeS. Thus, SO2 emissions and pollution were significantly eliminated. This work investigated the thermodynamic and experimental feasibility and phase conversion mechanism of this proposed method, the detailed lead extraction and sulfur fixing mechanisms were clarified, and the phase transformation and microstructural evolution processes were characterized. Additionally, a bench experiment of industrial, end-of-life LAB paste was conducted to detect the lead recovery and sulfur fixation efficiency.
INTRODUCTION Advances in the automobile, chemical, energy, transportation, and telecommunication industries are increasingly expanding both the demand for lead-acid batteries (LABs) and its scrap volume growth worldwide.1 The reported amounts of scrap LAB annually in China total > 2.6 million metric tons,1–3 around 1.79 Mt in the Americas4 and approximately 1.5 Mt in Europe.1,2 LABs are a solid waste and classified as hazardous materials in many countries. Their disposal has become a significant environmental concern.5 However, considering the shortage of primary lead ores, increasing interest is being shown in recycling lead from scrap LABs. Typically, an end-of-life LAB consists of four main components: waste electrolyte (11–30%), polymeric materials (22–30%), lead alloy grids (24– 30%), and lead paste (30–40%). Of these, lead paste is the most difficult to recycle.6 It is a mixture of 50– 60% PbSO4, 15–35% PbO2, 5–10% PbO/Pb(OH)2, 2– 5% metallic Pb, and a small amount of impurities, such as iron, antimony, tin, and barium.6
Lead produced in recycling increasingly dominates the world’s lead market.7 More than 95% of the LABs used in the US and Europe are recycled.8,9 In China, the production of secondary lead in 2018 was approximately 2.15 Mt, accounting for only 46% of total lead production. The recycling degree is alarming
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