Lithium Recovery from Metallurgical Slag via Neutralization
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Solution Overview
Problem
The recovery of lithium from lithium-bearing slags obtained during the pyrometallurgical treatment of lithium-ion batteries is complex and expensive due to issues like lithium aluminates precipitation and the formation of aluminum hydroxide flakes, which degrade the lithium recovery yield, and existing methods either fail to recover lithium or reduce the economic value of the slag by not addressing co-precipitation of aluminum and lithium during acid treatment.
Innovation Solution
A process that combines the spodumene processing flow sheet with the use of lithium-bearing metallurgic slag as a neutralizing agent, allowing for the substitution of conventional neutralizing agents and optimizing lithium release by adjusting pH levels, thereby reducing aluminum concentration and gypsum formation, and enhancing lithium recovery yield.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the slag is leached in acidic conditions to extract lithium, then lithium is released into the leachate, but aluminum is also partially soluble causing precipitation of lithium aluminates and formation of aluminum hydroxide flakes that adsorb lithium, degrading the lithium recovery yield
Solution Approach 1:
The patent applies preliminary action by adding a complexing agent before the acid leaching step. This complexing agent pre-binds with aluminum ions to form stable complexes, preventing aluminum from precipitating as hydroxide flakes or lithium aluminates during subsequent neutralization. The complexing agent is introduced in advance to modify the chemical environment before lithium extraction begins, thereby eliminating the harmful precipitation effect while maintaining high lithium recovery yield.
2Quantity of substance
If dilute sulfuric acid is used to prevent precipitation of lithium aluminates during neutralization, then lithium recovery is maintained, but the leachate requires expensive evaporation to concentrate before further processing
Solution Approach 1:
The patent uses preliminary action by adding a complexing agent before acid leaching that prevents aluminum precipitation throughout the process. This allows the use of concentrated acid leaching conditions without the need for subsequent evaporation, as the complexing agent continuously suppresses aluminum hydroxide formation even at higher acid concentrations. The preliminary complexation enables more efficient leaching without the energy-intensive evaporation step.
3Reliability
If conventional neutralizing agents are used to neutralize the acidic slurry, then pH is adjusted to precipitate impurities, but considerable amounts of gypsum are produced that cannot be valorized
Solution Approach 1:
The patent introduces a complexing agent as an intermediary substance that mediates between the aluminum ions and the neutralizing agent. This complexing agent binds aluminum ions to form stable complexes that remain in solution during neutralization, preventing the formation of aluminum hydroxide flakes and lithium aluminate precipitation. The intermediary complexing agent thus enables effective pH adjustment without the harmful side effects of conventional neutralization, and reduces gypsum waste by allowing alternative neutralizing approaches.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach significantly increases lithium recovery yield, reduces gypsum production, and maintains high lithium concentration in the leachate, ensuring efficient and economical lithium extraction with minimal lithium loss, as demonstrated in various examples where lithium recovery rates reach up to 100% and overall process economy is improved.
Implementation Method 1
neutralizing the acidic slurry to a pH between 5 and 7, by addition of at least one neutralizing agent... lithium-bearing metallurgic slag is added as neutralization agent
Implementation Method 2
reacting the beta variant with sulfuric acid... most of the lithium in the slag is released
Implementation Method 3
neutralizing the acidic slurry to a pH between 5 and 7... precipitating a number of impurities
Data Source
AI summary
A process is divulged for the recovery of lithium from metallurgic slags comprising the steps of roasting spodumene to convert it from the alpha to the beta variant; reacting the beta variant with sulfuric acid, using a stoichiometric excess of acid; repulping the reaction product with water, forming an acidic slurry; neutralizing the acidic slurry to a pH between 5 and 7, by addition of at least one neutralizing agent; filtrating the neutralized slurry, thereby obtaining a lithium bearing solution and a residue; characterized that, in either one or both of the steps of repulping and neutralizing the acidic slurry, lithium-bearing metallurgic slag is added as neutralization agent. The lithium-bearing metallurgic slag is used to substitute at least part of the classic neutralizing agent. The lithium in the slag is released, and added to the lithium liberated from the spodumene.