The Green Science Alliance in Japan has successfully extracted valuable metals from spent lithium-ion batteries using natural solvents.
Ryohei Mori at the alliance has developed a procedure to extract cobalt, nickel and manganese from cathode and black mass using a natural deep eutectic solvent.
This approach could replace toxic solvents such as sulphuric acid or strong organic solvents which are harmful to the environment. In addition, existing chemical processes often require high temperatures and emit corrosive vapours which can pose a danger to factory operators.
As a step towards commercial-scale industrial application, this innovative metal extraction process will be compared to that of conventional recycling methods. Green Science Alliance will continue to search for the best deep eutectic solvent and metal sedimentation process in order to achieve maximum efficiency in metals recovery.
Mori explains that a deep eutectic solvent has similar characteristics to that of ionic liquid. It is a mixture of Lewis or Bronsted acid and base materials. They contain various types of anion and cation.
Deep eutectic solvents can be synthesised by using certain ratios of hydrogen bond donor and accepter chemicals. By applying two or several chemical compounds, one can obtain eutectic substances which have lower melting points than any of the individual chemicals.
The good news is that the deep eutectic solvent used in these experiments is cheaper than ionic liquid in general. Application examples of deep eutectic solvents include:
- Electrolyte for battery
- Extraction of various type of plant derived materials such as catechin, flavonoid, anthraquinone, alkaloids etc.
- Solvent for various type of organic synthesis
- Extraction and deposition of various types of metal
- Gas absorption
- Dissolution of cellulose, lignin etc.
- Biofuel purification