Lithium Solution Purification via Precipitation and Extraction
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Solution Overview
Problem
Current lithium recovery processes from lithium-containing brines result in significant lithium losses due to co-precipitation with calcium and magnesium, and require expensive sodium carbonate, leading to increased investment costs from large equipment needs.
Innovation Solution
A two-stage process involving precipitation and liquid-liquid extraction to remove calcium and magnesium, using sodium carbonate and calcium hydroxide for initial precipitation, followed by selective extraction with dialkyl phosphoric acid to minimize lithium co-precipitation and eliminate the need for solution dilution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If sodium carbonate precipitation is used to remove magnesium and calcium from lithium-containing brine, then calcium and magnesium removal is achieved, but lithium losses increase due to co-precipitation
Solution Approach 1:
The invention divides the calcium and magnesium removal process into two distinct stages: first using sodium carbonate precipitation to remove the majority of calcium and magnesium, then using liquid-liquid extraction with organophosphoric acid to remove the remaining traces. This segmentation allows each stage to be optimized for its specific function, achieving high overall removal efficiency while minimizing lithium loss in the extraction stage where lithium co-precipitation is avoided.
Solution Approach 2:
The invention introduces an intermediary substance - organophosphoric acid (such as D2EHPA) - as the extracting agent in the liquid-liquid extraction stage. This intermediary selectively binds to remaining calcium and magnesium ions without precipitating lithium, thereby achieving trace removal while preserving lithium in the aqueous phase. The intermediary enables selective separation that the direct precipitation method cannot achieve.
2Quantity of substance
If sodium carbonate is used for precipitation to remove calcium and magnesium, then impurity removal is achieved, but production costs increase due to expensive chemical consumption
Solution Approach 1:
The invention applies partial action by using sodium carbonate precipitation only to remove the bulk (majority) of calcium and magnesium impurities, rather than attempting to remove all traces in this stage. The remaining trace amounts are then removed by the liquid-liquid extraction stage. This partial application of precipitation avoids excessive sodium carbonate consumption while achieving the required overall removal efficiency.
Solution Approach 2:
The invention replaces the expensive and lithium-loss-prone sodium carbonate precipitation method for trace removal with a more economical liquid-liquid extraction process using organophosphoric acid. The extraction agent can be regenerated and reused, making it a cost-effective solution for the final polishing stage of impurity removal.
3Quantity of substance
If conventional precipitation methods are used to remove calcium and magnesium, then impurity removal is achieved, but equipment size increases due to the need for large processing vessels
Solution Approach 1:
The invention replaces the conventional mechanical/chemical precipitation system with a liquid-liquid extraction system for the trace removal stage. Extraction processes typically require smaller equipment volumes compared to large-scale precipitation tanks, as extraction can be performed in more compact mixer-settler units or extraction columns. This substitution reduces the overall equipment footprint while maintaining high removal efficiency.
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 reduces lithium losses and investment costs by achieving high purity lithium carbonate with minimal co-precipitation of lithium, maintaining over 90% lithium yield and reducing equipment size requirements.
Implementation Method 1
precipitation step, in which a first part of magnesium and calcium is removed from the lithium-containing raw-material solution by precipitation
Implementation Method 2
extraction step, in which a second part of calcium and magnesium is removed from the lithium-containing solution obtained from the precipitation step by liquid-liquid extraction
Data Source
AI summary
The invention relates to a process for producing a lithium-containing solution from a lithium-containing raw-material solution, by: a) precipitating a first part of magnesium and calcium from the lithium-containing raw-material solution, b) extracting a second part of calcium and magnesium from the lithium-containing solution by liquid-liquid extraction, a resultant product being a lithium-containing solution. The invention also relates to equipment for producing a lithium-containing solution from a lithium-containing raw-material solution, including a precipitation unit to remove a first part of magnesium and calcium and an extraction unit to receive the lithium-containing raw-material solution and to remove therefrom a second part of calcium and magnesium by liquid-liquid extraction, and control unit to control the operation of the precipitation unit.