Selective cobalt and nickel separation by bioacid-mediated electrowinning

Area of Science:

• Materials Science and Engineering
• Electrochemistry
• Sustainable Chemistry

Background:

• Growing demand for cobalt (Co) and nickel (Ni) necessitates efficient separation from diverse sources.
• Electrowinning offers a greener alternative to solvent extraction for Co/Ni separation, but faces challenges due to similar reduction potentials.

Purpose of the Study:

• To develop a cost-effective and sustainable method for selective cobalt and nickel separation.
• To enhance the electrochemical separation of Co/Ni using bioacids to overcome limitations of similar reduction potentials.

Main Methods:

• Utilized cost-effective and recyclable bioacids to modify the solvation environments of Co and Ni ions.
• Investigated the effect of tartaric acid on selectivity, observing the formation of a dinuclear complex.
• Applied the bioacid-modified electrowinning process to ternary lithium-ion battery leachates in batch and scalable flow systems.

Main Results:

• Tartaric acid demonstrated the highest selectivity, amplifying the reduction potential difference between Co and Ni.
• Achieved 99.1% Co purity in batch mode separation.
• In a scalable flow system, achieved stepwise recovery of metallic Co (95.1%), Ni (96.5%), and manganese dioxide (~100%) with high yields.

Conclusions:

• Bioacid-modified electrowinning provides a sustainable and generalized electrochemical platform for selective Ni/Co separation.
• The process offers superior economic and environmental benefits compared to traditional methods.
• Enables efficient recycling of valuable metals from complex feedstocks like lithium-ion battery leachates.