Recovery of Excess Sulfuric Acid in the Lithium-Ion Batteries Recycling Process

Description

The widespread usage of lithium-ion batteries in electric vehicles has led to an increasing concern regarding their end-of-life management. Among the challenges in LIB recycling is the extraction of valuable materials like lithium, cobalt, and nickel. In the hydrometallurgy treatment of the black mass, these metals are first leached and then separated and purified. The leaching process requires significant amounts of excess sulfuric acid to achieve high yields. Acid is subsequently neutralized and the resulting sodium sulfate/ gypsum is wasted. The recovery of sulfuric acid is beneficial to reduce the consumption of neutralization agents (e.g., sodium hydroxide or calcium carbonate). Moreover, the regenerated acid can either be reused for the leaching process or the solvent extraction process, depending on the purity and concentration. In this work, the excess sulfuric acid is recovered by the solvent extraction process using tri-n-octyl amine (TOA) as an extractant. First, the influence of the phase modifiers 1-octanol, 2-ethylhexanol, and tributyl phosphate on the extraction yield is investigated. Subsequently, the thermodynamic properties like Gibb’s enthalpy, reaction enthalpy, and equilibrium constant are determined for both, sulfuric acid and LIB leachate. Since the co-extraction of iron in a sulfuric medium is mentioned in the literature [1], the metal concentration of various species is also investigated. The study revealed that TOA is capable of extracting 97.6 % of the sulfuric acid at a phase ratio of 4 and a volume fraction of 40 %. The addition of 20 vol % of 2-ethylhexanol has no impact on the extraction yield but prevents phase separation within the organic layer. The extraction of leachate exhibits an identical extraction behavior as the sulfuric acid/ TOA system. Furthermore, no co-extraction could be detected for any metal.

Period	14 Feb 2024
Event title	Jahrestreffen der DECHEMA/VDI-Fachgruppe Extraktion
Event type	Conference
Location	GermanyShow on map