Recycling alloy scrap and CO2 by paired molten salt electrolysis

Reclaiming valuable materials from retired alloys and CO2 in an eco-friendly and efficient manner is critically important to meet the urgent need for strategical metals and curb climate change. Herein, we report a molten salt electrolyzer with an alloy scrap anode along with a CO2 reduction cathode for co-recycling alloy scrap and CO2. In molten CaCl2-NaCl-CaCO3 at 700 degrees C, the alloy scrap is converted to porous oxide scale at the anode and CO2 is reduced to carbon at the cathode. The Cl- in the molten salt prevents the passivation and allows the continuous oxidation of the alloy scrap anode, and CO32- was electrochemically reduced to provide O2- while generating carbon. The average particle size of the anode oxides is about 8 mu m and the cathode carbon is amorphous structure. Furthermore, the obtained oxides can be converted to water-soluble sulfates by sulfation roasting with recovery rates of over 92% for both Co and Ni. More importantly, the paired electrolysis method improves energy efficiency by repurposing both waste alloy scrap and CO2. This paper provides a promising and green strategy to recover valuable metals from various alloy scrap and C/CO from carbon dioxide to close both metal and carbon cycles.

Automated summary

This study presents a molten salt electrolyzer approach for the simultaneous recovery of alloy scrap and CO2, enabling the reuse of valuable materials. The oxides in the molten salt and CO2 are converted to water-soluble sulfates and carbon, respectively, achieving high recovery rates. This method improves energy efficiency and closes the metal and carbon cycles.