Bipolar Membrane Electrochemical Magnesium Removal
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Solution Overview
Problem
Current methods for removing magnesium ions from salt lake brine, particularly those with high magnesium-to-lithium ratios, are inefficient due to poor mixing efficiency and high costs associated with sodium hydroxide use, leading to significant lithium resource loss and increased production costs.
Innovation Solution
A bipolar membrane electrochemical process is used for in situ alkali production, allowing for homogeneous generation and control of hydroxide groups, which react with magnesium ions in a direct-current electric field to form precipitable magnesium hydroxide particles in specialized mesh materials, reducing membrane fouling and eliminating the need for external sodium hydroxide handling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If sodium carbonate is added to remove magnesium ions through precipitation, then magnesium ions are removed, but lithium ions are also converted into lithium carbonate precipitate causing serious loss in resources
Solution Approach 1:
The patent changes the chemical parameter from carbonate-based precipitation to hydroxide-based precipitation. By using sodium hydroxide instead of sodium carbonate, the pH is adjusted to a range where magnesium hydroxide precipitates selectively without causing lithium carbonate formation, thus removing magnesium while preserving lithium resources
Solution Approach 2:
The patent employs a disposable mesh material that facilitates magnesium hydroxide precipitation and can be easily discarded or regenerated. This mesh material provides a large surface area for precipitation while being inexpensive and easy to replace, solving the problem of selective precipitation without costly complex systems
2Loss of substance
If sodium hydroxide is used for magnesium ion removal, then mixing efficiency improves and lithium loss reduces, but production costs increase
Solution Approach 1:
The system uses the brine itself as the electrolyte and utilizes the natural magnesium and chloride ions present in the salt lake brine. The electrochemical cell generates hydroxide ions in situ from the brine components, eliminating the need to import and handle expensive sodium hydroxide solutions, thus reducing production costs while maintaining high selectivity
Solution Approach 2:
The patent introduces an electrochemical cell with bipolar membrane as an intermediary system. This intermediary converts electrical energy into chemical energy to generate hydroxide ions on-demand, serving as a bridge between the brine and the precipitation process, thereby avoiding direct mixing of sodium hydroxide with brine and reducing costs
3Productivity
If conventional mixing methods are used for sodium hydroxide addition, then magnesium ion removal occurs, but mixing efficiency is poor leading to gelation and difficult removal
Solution Approach 1:
The patent replaces mechanical mixing methods with an electrochemical field-based system. Instead of mechanically mixing sodium hydroxide solution with brine, the system uses electrical fields to generate hydroxide ions in situ, which then react with magnesium ions. This eliminates poor mixing efficiency and gelation problems associated with mechanical mixing
Solution Approach 2:
The patent transitions from a zero-dimensional mixing approach (direct mixing of solutions) to a three-dimensional electrochemical reaction zone. The bipolar membrane creates distinct compartments where hydroxide ions are generated and then diffuse to react with magnesium ions, providing spatial control and improving mixing efficiency through mass transport rather than mechanical agitation
4Loss of substance
If external sodium hydroxide is used for precipitation, then magnesium ions are removed, but handling procedures increase complexity and cost
Solution Approach 1:
The system makes the brine self-sufficient by using its own components (magnesium ions, chloride ions, and water) as the electrolyte. The electrochemical cell generates the necessary hydroxide ions from the brine itself, eliminating the need for external sodium hydroxide handling, storage, and transportation infrastructure, thereby simplifying the overall system
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 approach achieves over 98% magnesium ion removal with minimal lithium loss and reduces production costs by 30-40% compared to traditional methods, enabling more efficient utilization of lithium resources from salt lake brine.
Implementation Method 1
bipolar membrane electrochemical process
Implementation Method 2
magnesium ions will react with hydroxide groups and generate magnesium hydroxide precipitate
Implementation Method 3
hydroxide groups and magnesium ions driven by direct-current electric field would migrate in opposite directions
Data Source
AI summary
The present invention provides a high-efficient magnesium ion removal system for salt lake brine based on in situ alkali production using bipolar membrane electrochemical process, it is constructed with cathode, cathode cell, anode, anode cell, and anion exchange membranes, bipolar membranes, acid cells, alkali cells, mesh materials for precipitate aggregation, acid-washing cells. During the working stage, salt lake brine enters the alkali cell, in which magnesium ions react with hydroxide groups and generate precipitate in mesh materials for precipitate aggregation, meanwhile magnesium-removed salt lake brine is produced; pure water enters acid cell, in which hydrochloric acid is produced and then exported to acid-washing cell; the mesh materials for precipitate aggregation, after they are packed with magnesium hydroxide particles, would be periodically transferred into acid-washing cell, in which magnesium hydroxide would react with hydrochloric acid and generate magnesium chloride solution, and the mesh materials are recycled after regeneration for precipitate aggregation.