AB5 Alloy Purification via Selective pH Dissolution
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Solution Overview
Problem
Current methods for recycling nickel/metal hydride batteries fail to efficiently separate and purify nickel hydroxide (Ni(OH)2 from hydrogen storage intermetallic alloy AB5, leading to contamination and reduced recovery of valuable lanthanum, which is crucial due to its limited availability and growing demand.
Innovation Solution
A process involving the selective dissolution of Ni(OH)2 using a carboxylic acid with 1-8 carbon atoms at a pH of 2.7 to 3.4 in an aqueous medium, followed by filtration, washing, and drying under an inert atmosphere, allowing for the separation and purification of AB5 alloy and lanthanum without dissolving the intermetallic alloy, and further upgrading through sodium metal reduction or hydrogen treatment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional liquid/liquid extraction methods are used to dissolve nickel and cobalt, then metal recovery is achieved, but nickel hydroxide cannot be selectively separated from the AB5 alloy
Solution Approach 1:
The patent applies parameter changes by carefully controlling the pH of the aqueous solution within a specific range (2.7-3.4) to achieve selective dissolution of nickel hydroxide while preserving the AB5 alloy. This precise parameter control enables differentiation between similar materials based on their distinct chemical properties at controlled pH levels.
Solution Approach 2:
The patent introduces an intermediary substance (aqueous solution at controlled pH) that mediates the selective dissolution process. This intermediary enables the separation of nickel hydroxide from the AB5 alloy by creating conditions where only the hydroxide dissolves, acting as a selective transport medium for nickel separation.
2Productivity
If strong acids are used to dissolve nickel hydroxide, then separation efficiency increases, but the AB5 intermetallic alloy also dissolves causing loss of valuable lanthanum
Solution Approach 1:
The patent transforms the dissolution approach by changing from strong acid conditions to controlled pH aqueous solutions. This parameter change maintains separation efficiency through selective chemistry while preventing unwanted dissolution of the AB5 alloy, thereby preserving valuable lanthanum content.
Solution Approach 2:
The patent converts the potential harm of acid dissolution into a benefit by using mild aqueous solutions at controlled pH. Instead of causing unwanted dissolution, the controlled pH conditions exploit the specific solubility characteristics of nickel hydroxide to achieve selective separation while protecting the AB5 alloy integrity.
3Speed
If pH is not controlled during dissolution, then processing speed increases, but selective separation of nickel hydroxide cannot be achieved
Solution Approach 1:
The patent establishes pH control (2.7-3.4) as a critical process parameter that enables both reasonable processing speed and high selective separation. The controlled pH creates optimal conditions for nickel hydroxide dissolution kinetics while maintaining AB5 alloy stability, achieving both speed and precision simultaneously.
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 effectively separates and purifies AB5 alloy and lanthanum, achieving high purity and enabling the reuse of AB5 in electronic devices while minimizing contamination and preserving the integrity of the alloy, thus addressing the critical raw material scarcity and cost issues.
Implementation Method 1
selectively dissolving Ni(OH)2 from the recovered AB5 containing mixture with a carboxylic acid having 1-8 carbon atoms and maintaining a pH of about 2.7 to 3.4 in an aqueous media without dissolving the AB5 intermetallic alloy and lanthanum
Implementation Method 2
The solids of step (d) may be treated with hydrogen or a sodium metal to remove any metal oxide
Data Source
AI summary
The invention relates to the purification of recovered AB5 alloy which is obtained from spent nickel/metal hydride storage batteries by the selective removal of any Ni(OH)2 and the recovery of lanthanum without dissolving any AB5 alloy.