Lithium Chloride Purification via HCl Sparging and Electrolysis
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Solution Overview
Problem
Existing processes for producing lithium hydroxide and lithium carbonate are inefficient in removing impurities, resulting in relatively impure products, especially when aiming for high-quality or battery-grade materials.
Innovation Solution
A process involving an HCl sparging step as an impurity removal method, followed by electrolysis of a lithium chloride solution, which eliminates the need for a concentration step and fractional crystallization, using precious metal containing MMO electrodes to enhance efficiency and recover hydrochloric acid.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional impurity removal methods (precipitation, evaporation ponds, fractional crystallisation) are used, then the process is simpler and lower cost, but the product purity is insufficient for battery grade requirements
Solution Approach 1:
The patent extracts and removes specific impurity elements (Fe, Mg, Mn, Al, Ca, Na, K) through selective precipitation reactions using lime and soda ash, followed by filtration. This targeted extraction approach achieves battery-grade purity (99.5% Li2CO3 or 99% LiOH) by systematically removing each category of impurities rather than relying on simple evaporation or crystallisation methods.
Solution Approach 2:
The patent replaces mechanical/physical separation methods (evaporation ponds, fractional crystallisation) with chemical precipitation and filtration methods. Instead of relying on slow evaporation or complex crystallisation sequences, the process uses chemical reactions to precipitate impurities as insoluble hydroxides and carbonates, which are then removed by filtration, significantly improving purity while simplifying the overall process flow.
2Manufacturing precision
If concentration step with isopropanol solvent extraction is used, then lithium chloride can be concentrated to 99.9% purity, but the reagent cost is high and the process is problematic due to flammability
Solution Approach 1:
The patent replaces the expensive and hazardous isopropanol solvent with inexpensive, non-flammable aqueous solutions of lime (Ca(OH)2) and soda ash (Na2CO3). These reagents are added in controlled amounts to precipitate impurities, and their byproducts are easily managed. This substitution eliminates flammability risks and reduces reagent costs while achieving the same purification objective.
Solution Approach 2:
The patent changes the chemical parameters of the purification system by using aqueous chemistry instead of organic solvent extraction. The pH, ionic composition, and reaction conditions are optimized to enable selective precipitation of impurities. This parameter change transforms a hazardous, expensive process into a safe, economical one while maintaining high purification effectiveness.
3Productivity
If HCl sparging is used for impurity removal, then operational costs are reduced and efficiency is improved, but the process requires precise control of gas sparging parameters
Solution Approach 1:
The patent incorporates pH monitoring and control during the HCl sparging process to maintain optimal conditions for impurity removal. By continuously monitoring pH and adjusting HCl gas sparging rates accordingly, the process achieves consistent impurity removal efficiency while preventing excessive acidification that could dissolve precipitated impurities or create hazardous conditions. This feedback control simplifies operation by providing clear process guidance.
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 process achieves high purity lithium hydroxide and lithium carbonate products with reduced operational costs and improved efficiency by effectively removing impurities, including sodium and potassium, and recovering HCl acid with high recovery rates.
Implementation Method 1
an HCl sparging step, thereby providing a substantially purified lithium chloride solution
Implementation Method 2
an HCl sparge is utilised as an impurity removal step
Implementation Method 3
Passing the purified lithium chloride solution of step (ii) to an electrolysis step thereby producing a lithium hydroxide solution
Implementation Method 4
The lithium hydroxide solution produced in step (iii) is carbonated by passing compressed carbon dioxide through the solution, thereby producing a lithium carbonate precipitate
Data Source
AI summary
A process (10) for the treatment of a lithium containing material (12), the process comprising the steps of:(i) Preparing a process solution from the lithium containing material (12);(ii) Passing the process solution from step (i) to a series of impurity removal steps, one of which is an HCl sparging step 58, thereby providing a substantially purified lithium chloride solution; and(iii) Passing the purified lithium chloride solution of step (ii) to an electrolysis step (70) thereby producing a lithium hydroxide solution.An additional step in which the lithium hydroxide solution produced in step (iii) is carbonated by passing compressed carbon dioxide (88) through the solution, thereby producing a lithium carbonate precipitate, is also disclosed.