Cobalt-Nickel Hydroxide Separation by Alkaline Aluminum Leaching
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Solution Overview
Problem
Existing methods for recovering cobalt and nickel from lithium ion battery waste face issues such as process loss due to cobalt and nickel forming hydroxides alongside aluminum, leading to insufficient aluminum separation and increased processing costs from using organic solvents like PC-88A.
Innovation Solution
A method involving adjusting the pH of an acidic solution containing aluminum, cobalt, and nickel to 5-7 to form hydroxides, followed by solid-liquid separation, leaching aluminum with an alkaline solution at pH 8 or more, and recovering cobalt and nickel hydroxides through solid-separation, thereby selectively separating aluminum and increasing the recovery ratio of cobalt and nickel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If aluminum is separated by adjusting pH to precipitate hydroxides, then aluminum removal is achieved, but cobalt and nickel also form hydroxides causing process loss
Solution Approach 1:
The patent divides the aluminum removal process into two distinct stages: first precipitating aluminum hydroxide at controlled pH, then selectively leaching it with alkaline solution. This segmentation allows cobalt and nickel to remain in the solid phase during leaching, preventing their loss while achieving complete aluminum removal.
Solution Approach 2:
Instead of directly recovering cobalt and nickel from the precipitate, the patent inverts the approach by selectively dissolving aluminum hydroxide with alkaline solution, leaving cobalt and nickel hydroxides intact. This inversion enables separation without losing the valuable metals.
2Loss of substance
If hydroxides are acid-dissolved to recover process loss, then cobalt and nickel are recovered, but aluminum hydroxide is also dissolved returning to leachate
Solution Approach 1:
The patent inverts the conventional approach by using alkaline solution instead of acid to dissolve the hydroxides. Since aluminum hydroxide is soluble in alkaline solution while cobalt and nickel hydroxides are not, this inversion achieves selective aluminum removal without redissolving the valuable metals.
Solution Approach 2:
The patent changes the chemical parameter from acidic to alkaline conditions for the leaching step. This parameter change exploits the different solubility characteristics of aluminum hydroxide versus cobalt and nickel hydroxides in alkaline environments, enabling selective separation.
3Reliability
If organic solvent extraction is used to separate aluminum, then aluminum removal is achieved, but processing cost increases and operation becomes complicated
Solution Approach 1:
The patent replaces expensive organic solvents like PC-88A with a simple, inexpensive alkaline solution (sodium hydroxide). This substitution maintains effective aluminum separation while dramatically reducing processing costs and operational complexity.
Solution Approach 2:
The patent changes the separation mechanism from organic solvent extraction to alkaline leaching, exploiting the amphoteric nature of aluminum hydroxide. This parameter change simplifies the process by using a common chemical reagent instead of specialized organic solvents.
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 efficiently separates aluminum from cobalt and nickel, reducing process losses and operational complexity, and enhances the recovery ratio of cobalt and nickel by avoiding the use of costly organic solvents.
Implementation Method 1
mixing the recovered hydroxides with an alkaline solution, and leaching aluminum contained in the hydroxides under a liquid condition of pH 8 or more
Implementation Method 2
adjusting pH of the acidic solution to 5 to 7, and converting the cobalt, the nickel and the aluminum into hydroxides thereof
Data Source
AI summary
A method of recovering cobalt and nickel includes the steps of: adding alkaline to an acidic solution containing aluminum together with cobalt and nickel, adjusting pH of the acidic solution to 5 to 7, and converting the cobalt, the nickel and the aluminum into hydroxides thereof; recovering the hydroxides by solid-liquid separation, mixing the recovered hydroxides with an alkaline solution, and leaching aluminum contained in the hydroxides under a liquid condition of pH 8 or more; and recovering a cobalt hydroxide and a nickel hydroxide that aluminum is separated therefrom by solid-separation on a leachate.