Aluminum Solvent Extraction at Low pH to Prevent Hydroxide Precipitation
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Solution Overview
Problem
Existing methods for extracting aluminum from acid dissolution solutions in waste lithium-ion batteries result in aluminum precipitation, leading to reduced recovery rates of lithium, cobalt, and nickel due to co-precipitation, and the inability to effectively separate aluminum without causing precipitation.
Innovation Solution
A method involving mixing the acid dissolution solution with an organic solvent containing mono-2-ethylhexyl (2-ethylhexyl)phosphonate at an equilibrium pH less than 1.8 to extract aluminum without precipitation, followed by a fluorine separation and removal step to adjust pH to 2 to 7 for solid-liquid separation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the equilibrium pH is adjusted to 1.8 or more to extract aluminum using an organic solvent, then aluminum can be separated from the acid dissolution solution, but aluminum hydroxide precipitates locally in the tank and does not completely redissolve, preventing precise separation
Solution Approach 1:
The patent changes the pH parameter from the conventional range (1.8-3.0) to a lower range (0.5-1.8), specifically achieving effective aluminum separation at pH 1.8 or less. This parameter change prevents aluminum hydroxide precipitation while maintaining extraction efficiency, as evidenced by the aluminum concentration in the aqueous phase being 99.9% or more when pH is controlled at 1.8 or less
2Manufacturing precision
If the equilibrium pH is adjusted to 1.8 or more to extract aluminum, then aluminum separation is achieved, but cobalt and nickel coprecipitate with aluminum, reducing their recovery rates
Solution Approach 1:
The patent applies parameter changes by controlling the equilibrium pH at 1.8 or less during solvent extraction. This prevents the coprecipitation of cobalt and nickel with aluminum, as the lower pH keeps these metals in solution while still enabling aluminum to be extracted into the organic phase. The result is high recovery rates for lithium, cobalt, and nickel while achieving effective aluminum separation
3Manufacturing precision
If aluminum is precipitated as hydroxide to separate it from the acid dissolution solution, then aluminum can be removed, but the metal to be recovered co-precipitates, resulting in a decrease in the recovery rate of the metal to be recovered
Solution Approach 1:
Instead of the conventional approach of raising pH to precipitate aluminum hydroxide for separation, the patent inverts the approach by using solvent extraction at low pH (1.8 or less). In this inverted method, aluminum is extracted into the organic phase while remaining in solution, and no hydroxide precipitation occurs. This eliminates the coprecipitation problem and achieves high recovery rates for lithium, cobalt, and nickel
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 method allows for efficient extraction of aluminum without precipitation, improving the recovery rates of valuable metals like lithium, cobalt, and nickel, and enables effective separation of fluorine, thereby enhancing the overall recovery process.
Implementation Method 1
mixing an acid dissolution solution containing aluminum with an organic solvent containing mono-2-ethylhexyl (2-ethylhexyl)phosphonate, and extracting aluminum from the acid dissolution solution under the condition of an equilibrium pH less than 1.8
Implementation Method 2
adjusting the equilibrium pH to 2 to 7 to generate aluminum hydroxide, thereby coprecipitating fluorine for solid-liquid separation
Data Source
AI summary
An object to be solved by the present invention is to provide a method for extracting aluminum from an acid dissolution solution without causing precipitation of aluminum. The method for extracting aluminum of the present invention includes an aluminum extraction step of mixing an acid dissolution solution containing aluminum with an organic solvent containing mono-2-ethylhexyl (2-ethylhexyl)phosphonate, and extracting aluminum from this acid dissolution solution under the condition of an equilibrium pH less than 1.8. If this acid dissolution solution further contains fluorine, the method for extracting aluminum of the present invention includes a fluorine separation and removal step of adjusting the aluminum concentration of the raffinate in an arbitrary range, and adjusting the equilibrium pH to 2 to 7 to generate aluminum hydroxide, thereby coprecipitating fluorine for solid-liquid separation.