Cobalt-Nickel Separation by pH-Staged Sulfide Precipitation
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Solution Overview
Problem
Existing methods for separating cobalt and nickel from lithium ion secondary batteries are complicated and costly due to the simultaneous removal of other metals, requiring multiple steps and high costs.
Innovation Solution
A method involving crushing and sorting, leaching with sulfuric acid and hydrogen peroxide, followed by copper separation using hydrogen sulfide compounds, and cobalt/nickel separation with alkali metal hydroxides to selectively precipitate sulfides, allowing for high-accuracy separation in fewer steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional acid leaching with oxidizing agents and pH adjustment is used to remove impurity elements, then metals are leached from the positive electrode active material, but cobalt and nickel are removed together with other metals requiring multiple subsequent separation steps
Solution Approach 1:
The invention segments the metal removal process into distinct stages: first removing copper selectively at low pH, then removing other impurity metals at higher pH, while preserving cobalt and nickel in the solution. This segmentation allows each metal to be removed in separate controlled steps rather than all at once, reducing subsequent separation complexity.
Solution Approach 2:
The invention utilizes parameter changes, specifically pH adjustment, to control metal precipitation selectively. By maintaining pH below 1.0 during initial leaching, copper precipitates as sulfide while cobalt and nickel remain soluble. Subsequent pH increases to 2.0-5.0 allow selective precipitation of other impurity metals, demonstrating parameter-based separation.
2Manufacturing precision
If multiple separation steps are used to separate cobalt and nickel from other metals, then high purity cobalt and nickel can be recovered, but the recovery cost increases
Solution Approach 1:
The invention performs preliminary removal of impurity metals (copper, aluminum, manganese, iron) before the final cobalt-nickel separation. By pre-cleaning the solution through controlled pH precipitation steps, the subsequent cobalt-nickel separation requires fewer additional purification steps, reducing overall processing cost while maintaining high purity.
Solution Approach 2:
The invention uses hydrogen sulfide compound as an intermediary reagent to selectively precipitate different metals at different pH stages. This intermediary enables controlled separation without requiring complex equipment or multiple chemical systems, simplifying the overall process while achieving high purity separation.
3Ease of operation
If pH is adjusted and precipitates are formed to remove impurity elements, then solid-liquid separation can be carried out, but cobalt and nickel are removed together with other metals in the same step
Solution Approach 1:
The invention applies local quality control by creating different chemical environments (different pH levels) for different separation stages. At pH < 1.0, copper is selectively precipitated; at pH 2.0-5.0, other impurity metals precipitate; and at higher pH, cobalt and nickel precipitate together. This localized pH control ensures that each precipitation step targets specific metals, preventing unwanted co-precipitation.
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
Enables accurate separation of cobalt and nickel from other metals with a reduced number of steps and lower costs, achieving high yields of over 95% recovery.
Implementation Method 1
a leaching step of immersing the electrode material in a processing liquid containing sulfuric acid and hydrogen peroxide to obtain a leachate
Implementation Method 2
a copper separation step of adding a hydrogen sulfide compound to the leachate with stirring and subsequently carrying out solid-liquid separation to obtain an eluate containing cobalt and nickel and a residue containing copper sulfide
Implementation Method 3
a cobalt/nickel separation step of adding an alkali metal hydroxide to the eluate to adjust a pH and subsequently, adding a hydrogen sulfide compound with stirring and carrying out solid-liquid separation to obtain a precipitate containing cobalt sulfide and nickel sulfide
Implementation Method 4
adding an alkali metal hydroxide to the eluate to adjust a pH and subsequently, adding a hydrogen sulfide compound with stirring and carrying out solid-liquid separation to obtain a precipitate containing cobalt sulfide and nickel sulfide
Data Source
AI summary
What is provided is a method for separating cobalt and nickel including: a crushing and sorting step of crushing and classifying the lithium ion secondary battery to obtain an electrode material containing at least cobalt, nickel, copper, and lithium; a leaching step of immersing the electrode material in a processing liquid containing sulfuric acid and hydrogen peroxide to obtain a leachate; a copper separation step of adding a hydrogen sulfide compound to the leachate with stirring and subsequently carrying out solid-liquid separation to obtain an eluate containing cobalt and nickel and a residue containing copper sulfide; and a cobalt/nickel separation step of adding an alkali metal hydroxide to the eluate to adjust a pH and subsequently, adding a hydrogen sulfide compound with stirring and carrying out solid-liquid separation to obtain a precipitate containing cobalt sulfide and nickel sulfide and a residual liquid containing lithium.