Li-Na Ion Separation via Bipolar Membrane Electrolysis
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Solution Overview
Problem
Current methods for recycling lithium-ion/polymer batteries face challenges in effectively separating lithium (Li) and sodium (Na) ions from sulfate-containing solutions, making quantitative recovery of lithium economically impractical due to solubility ratios.
Innovation Solution
Converting sulfate-containing solutions into hydroxides through electrolysis and subsequent treatment with a carbonate source, specifically using membrane electrolysis with bipolar membranes, followed by separation and purification of Li2CO3, which is less soluble than Na2CO3, allowing for effective ion separation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If conventional precipitation methods are used to recover lithium from sulfate-containing solutions, then lithium can be recovered as Li2CO3, but the presence of Na2SO4 and Na2CO3 makes separation extremely complex and quantitative recovery economically impractical
Solution Approach 1:
The patent changes the chemical form of lithium and sodium from sulfate salts to hydroxide salts through electrolysis. This parameter change transforms Li2SO4 and Na2SO4 into LiOH and NaOH, which then react with carbonate to form Li2CO3 precipitate while Na2CO3 remains soluble, enabling effective separation that was not possible with the original sulfate form
Solution Approach 2:
The patent introduces an intermediary substance (carbonate, specifically Na2CO3 or CO2) that selectively reacts with lithium hydroxide to form insoluble lithium carbonate. This intermediary enables the separation by exploiting the solubility difference between Li2CO3 and Na2CO3, allowing lithium to precipitate while sodium remains in solution
2Loss of substance
If electrolysis is used to convert sulfate salts to hydroxides, then lithium and sodium can be effectively separated based on solubility differences, but energy consumption increases
Solution Approach 1:
The patent utilizes phase transitions during electrolysis, where electrical energy drives the conversion of dissolved sulfate ions to hydroxide ions and hydrogen gas. This phase/chemical transition enables the fundamental chemical transformation needed for separation, converting Li2SO4/Na2SO4 into LiOH/NaOH form that can be selectively precipitated
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 enables efficient and economic recovery of lithium by leveraging solubility differences, allowing for the effective separation and purification of Li2CO3, thereby facilitating sustainable lithium recycling from lithium-ion/polymer batteries.
Implementation Method 1
an aqueous solution A comprising Na2SO4 and Li2SO4 is subjected to electrolysis to obtain a solution B
Implementation Method 2
The separation takes place in an electrolysis cell with a bipolar membrane in the middle. A solution to be separated is applied to the electrolysis cell and the ions migrate to the oppositely charged sides of the membrane
Implementation Method 3
the resulting solution B is treated with a carbonate source to form Li2CO3
Implementation Method 4
While the solubilities of Na2SO4 and Li2SO4 differ only by a factor of 2, Li2CO3 is significantly less soluble than Na2CO3, which allows for a more effective separation of the two metals
Data Source
Figure 1~3
AI summary
The present invention relates to a method for separating Li and Na ions from sulfate-containing solutions and to a device for carrying out the method.