Lithium Brine Membrane Concentration Below Osmotic Pressure
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Solution Overview
Problem
Conventional processes for concentrating lithium sulfate from secondary mining process streams are complex, energy-intensive, costly, and result in inefficient lithium recovery.
Innovation Solution
A multi-stage membrane-based process using sequential membrane separation stages with pre-treatment and nanofiltration membranes operating at pressures below osmotic pressure to concentrate lithium sulfate, precipitating other salts and combining retentates to obtain a high-concentration lithium solution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If conventional evaporation and crystallization processes are used to concentrate lithium sulfate, then lithium recovery can be achieved, but the process becomes complex, energy-intensive, and costly
Solution Approach 1:
The patent replaces thermal evaporation and crystallization processes with membrane-based separation technology. Specifically, it uses a combination of loose nanofiltration membrane and tight nanofiltration membrane to separate lithium sulfate from other salts through size exclusion and charge-based rejection mechanisms, eliminating the need for high-energy heating and evaporation steps while achieving comparable or superior lithium recovery efficiency
Solution Approach 2:
The patent employs porous nanofiltration membranes with specific pore sizes and charge characteristics to selectively retain lithium sulfate while allowing other salts to pass through. The loose nanofiltration membrane (LFN) and tight nanofiltration membrane (TFN) work in sequence to concentrate lithium sulfate efficiently without requiring thermal energy input, thus resolving the contradiction between recovery efficiency and energy consumption
2Loss of substance
If conventional evaporation and crystallization processes are used to concentrate lithium sulfate, then lithium recovery can be achieved, but the process complexity increases and operational costs rise
Solution Approach 1:
The patent replaces complex multi-step evaporation and crystallization processes with a simplified two-stage membrane filtration system. The sequential arrangement of loose nanofiltration membrane followed by tight nanofiltration membrane creates a straightforward操作流程 that achieves lithium sulfate concentration and purification in a single continuous process, reducing both equipment complexity and operational complexity while maintaining high lithium recovery efficiency
3Quantity of substance
If conventional reverse osmosis processes operating above osmotic pressure are used, then salt separation can be achieved, but energy consumption and operational costs increase
Solution Approach 1:
The patent changes the operating pressure parameter from above-osmotic-pressure (conventional reverse osmosis) to below-osmotic-pressure operation. By using loose nanofiltration membrane with larger pore sizes and appropriate charge characteristics, the system achieves effective salt separation at lower pressures, reducing energy consumption while maintaining separation efficiency. The membrane's inherent properties enable this parameter change without sacrificing performance
Solution Approach 2:
The patent uses different nanofiltration membranes with locally optimized properties for different separation stages. The loose nanofiltration membrane is specifically designed with larger pores and charge characteristics suitable for low-pressure operation and preliminary separation, while the tight nanofiltration membrane provides final polishing. This local optimization of membrane properties enables efficient salt separation at reduced energy costs
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
The method achieves cost-effective and energy-efficient lithium concentration and recovery, with lithium sulfate concentration increasing from 1-2 wt.% to 8-10 wt.% while reducing energy consumption and operational costs.
Implementation Method 1
introducing the feed brine solution to a pre-treatment membrane at a pressure that is less than the osmotic pressure of the feed brine solution to obtain an initial permeate that passes through the pre-treatment membrane and an initial retentate that does not pass through the pre-treatment membrane
Implementation Method 2
introducing the initial permeate to a nanofiltration membrane at a pressure that is less than the osmotic pressure of the initial permeate to obtain a final permeate that passes through the nanofiltration membrane and a final retentate that does not pass through the nanofiltration membrane
Implementation Method 3
A precipitate of at least one of the salts other than lithium sulfate is included in the initial retentate if the solubility limit is exceeded depending on composition and operating conditions such as pH and temperature
Data Source
AI summary
A method of concentrating lithium containing solutions includes inputting a feed brine solution to an initial separation stage, the feed brine solution including lithium sulfate and one or more of sodium sulfate, potassium sulfate, calcium sulfate, and sodium chloride dissolved in water. In the initial separation stage, the feed brine solution is introduced to a pre-treatment membrane at a pressure that is less than the osmotic pressure of the feed brine solution. An initial permeate that passes through the pre-treatment membrane becomes the feed to a final separation stage, and an initial retentate that does not pass through the pre-treatment membrane includes a precipitate of at least one of the salts other than lithium sulfate. In the final separation stage, the initial permeate is introduced to a nanofiltration membrane at a pressure that is less than the osmotic pressure of the initial permeate. A final retentate that does not pass through the nanofiltration membrane is combined with the initial retentate to obtain a product solution having a higher concentration of dissolved lithium sulfate than the feed brine solution.