Solvent Extraction of Sulfuric Acid from Lithium-Ion Battery Leachate

Description

The hydro-metallurgical processing of spent lithium-ion batteries (LIB) aims the extraction and separation of value materials from the black mass, a recycling fraction consisting of both the cathode and anode active material. Typical representatives are lithium cobalt oxide (LCO), lithium nickel manganese cobalt oxide (NMC), or lithium nickel cobalt aluminium oxide (NCA). As the metals are present as oxides, physical separation methods fail and a chemical process, here hydro-metallurgy, must be used instead. The hydro-metallurgical treatment can be subdivided into the leaching, the purification, and the extraction of the value materials. While the leaching is carried out at a strong acidic regime, the purification requires pH values in the low acidic to neutral range. An alternative is the extraction of sulphate from the leachate. In this study, tri-n-octyl amine (TOA) is used as an anionic liquid ion exchanger/ extractant dissolved in Shellsol D70 as a solvent. The effect of the phase modifiers 1-octanol, 2-ethylhexanol, and tributyl phosphate on the extraction yield is studied first. Then, thermodynamic properties like Gibb’s enthalpy, reaction enthalpy, and equilibrium constant are determined for both, sulfuric acid and LIB leachate. As the co-extraction of iron in sulfuric medium is mentioned in the literature [1], the metal concentration of various species is studied, too. It showed that TOA is capable of extracting 97.6 % of the sulfuric acid at a phase ratio of 4 and a volume fraction of 40 % TOA. The addition of 20 vol% of 2-ethylhexanol does not impact the extraction yield but prevents phase separation within the organic layer. The extraction of leachate exhibits identical extraction behaviour as the sulfuric acid/ TOA system. By analysis of water-content in the organic phase by Karl-Fischer titration, it could be shown, that the extraction of sulfuric acid is associated with the co-extraction of water. Major impurities are aluminium and cobalt.

Period	26 Aug 2024
Event title	unbekannt/unknown
Event type	Other
Location	Czech RepublicShow on map