Iron scrap, a sustainable reducing agent for waste lithium ions batteries leaching: An environmentally friendly method to treating waste with waste

Current paper introduces the iron scrap as a sustainable, economic and efficient reducing agent for cobalt, nickel, and lithium leaching from waste lithium ion batteries (LIBs). In this novel method, a reducing leaching environment was provided by releasing ferrous ions (Fe2+) from iron scrap dissolution. The effect of iron scrap concentration, solid content and reaction time were investigated in leaching process. The results showed that using iron scrap increases the cobalt and nickel dissolution significantly; while it has negligible influence on lithium recovery. The highest cobalt (99.1%), nickel (94.9%) and lithium (90.5%) recoveries were obtained at iron scrap concentration = 25 g/l, solid content = 10 g/l, leaching time = 150 min. The added iron then was removed from pregnant leach solution (PLS) by controlling the pH. The results showed that iron was removed efficiently at pH=4, without other metals co-precipitation. After iron removal, cobalt and nickel are recovered from PLS by cementation method with zinc scrap. The results showed that cobalt-nickel mixture can be produced with zinc cementation, without any manganese, lithium and iron impurities. Finally, a conceptual process flow diagram (PFD) is proposed for waste LIBs recycling. This PFD which includes grinding, physical separation, leaching and metals recovery from pregnant leach solution is a full flowsheet to recycle all valuable metals from LIBs.

Automated summary

This paper presents the use of iron scrap as a sustainable, economic, and efficient reducing agent for leaching cobalt, nickel, and lithium from waste lithium ion batteries. The study investigated the effect of iron scrap concentration, solid content, and reaction time on the leaching process, achieving the highest cobalt, nickel, and lithium recovery rates under specific conditions. Iron was efficiently removed from the pregnant leach solution at pH=4, and cobalt and nickel were recovered using the cementation method with zinc scrap, producing a mixture free of manganese, lithium, and iron impurities.