Recovery of Cobalt Sulfate and Sulfuric Acid by Membrane Distillation Crystallization

Description

Recycling of spent lithium-ion batteries is subject of current research due to the rising importance of the circular economy. Elements of interest are cobalt, lithium, manganese, and nickel which are present in the black mass, a fraction within the mechanical recycling. Those metals are present as mixed oxides, which makes a chemical treatment necessary. Typical approach is the leaching in sulfuric acid and a subsequent solvent extraction to isolate the metals. This process yields dilute salt solutions (e.g., cobalt sulfate) that are fed either to electrowinning or to crystallization. Membrane distillation crystallization (MDC) is a sustainable and ongoing method for treating wastewater while recovering salt and water. The MDC operates within the temperature range of 50 – 60 °C, eliminating the need to heat to the boiling point and thus saving energy. A hydrophobic membrane separates the liquid from the vapor and guarantees a stable interfacial area. The modular setup is beneficial for the scale-up. MDC is used within the recycling process of lithium-ion batteries. The stripping solution from the solvent extraction of cobalt represents the feed solution for the MDC. Main components of this solution are cobalt sulfate and dilute sulfuric acid. The aim of the MDC is to concentrate the feed to the solubility limit and thus initiate crystallization. The obtained cobalt sulfate crystals are characterized by crystal morphology and purity. The resulting concentrated sulfuric acid will be reused as leaching acid within the recycling process. High-quality distillate is produced.The demonstration is conducted on a tubular PP capillary membrane with an inner diameter of 5.5 mm, an internal diameter 1.5 mm wall thickness, 0.2 μm pore diameter, 72 % porosity, and a total length of 300 mm. The membrane is embedded in a 30 mm inner diameter copper cooling tube. The MDC is operated at a characteristic feed volumetric flux of 1.2 L min-1 at ambient pressure.

Period	22 Feb 2024
Event title	Jahrestreffen der DECHEMA-Fachgruppe Membrantechnik
Event type	Conference
Location	GermanyShow on map