Recovery of metal aluminum by electrolysis of AlCl3-NaCl-LiCl-KCl molten salt
Over the past few decades,aluminium alloys have been used in a large number of applications in packaging,transport,aerospace and other areas,making them the second most important metallic material after steel.Because of their good corrosion resistance,aluminum alloys can be recycled after reaching the end of their useful life.The recycling of aluminum alloys has the double important significance of saving resources and environmental protection.The traditional cryolite electrolytic alumina process consumes a lot of energy and releases a lot of greenhouse gases.Remelting and recycling of end-of-life aluminum alloys can reduce energy consumption and carbon emissions,but this method affects the purity of the recycled aluminum.Recycling of scrap aluminum by molten salt electrolysis not only reduces energy consumption and carbon emissions,but also improves the purity of the recycled aluminum.In this work,AlCl3-NaCl-LiCl-KCl was used as the electrolyte for aluminum deposition on pure aluminum sheet with scrap aluminum alloy as the anode.The effect of experimental conditions such as current density,electrolysis temperature,and electrolysis time on the recovered metallic aluminum products were investigated,and the electrochemical mechanism of aluminum recovery in AlCl3-NaCl-LiCl-KCl molten salt was analyzed.It was shown that the current efficiency in scrap aluminum alloy could reach 97.3％and the purity of aluminum obtained was about 99.4wt％under the conditions of electrolysis temperature of 100℃,current density of 30 mA/cm2,and electrolysis for 3 h.The cyclic voltammetry curve indicated that only aluminum was involved in the reaction process,and the deposition potential of aluminum was about-0.3 V(vs.Al),and the scrap aluminum alloy dissolved under the action of the current and reacted with AlCl4-in the electrolyte to form Al2Cl7-,and Al2Cl7-near the cathode gained electrons to form an aluminum deposition layer on the cathode surface.
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