Rare Metal Salt Recovery via Acid-Stable Membrane Separation
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Solution Overview
Problem
Current methods for recovering rare metals like lithium, cobalt, and nickel from lithium ion batteries face challenges in long-term stability of nanofiltration membranes in acidic solutions and low recovery efficiency due to poor selective separability of monovalent and polyvalent metals.
Innovation Solution
A method involving acid treatment, followed by separation using a nanofiltration membrane under specific conditions, and concentration using a reverse osmosis membrane to effectively separate and recover rare metals, with pretreatment steps involving microfiltration or ultrafiltration to prevent membrane clogging and enhance selectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a nanofiltration membrane is used for separating rare metals in acidic aqueous solution, then separation of monovalent and polyvalent rare metals can be achieved, but the membrane shows poor long-term stability and low selective separability
Solution Approach 1:
The patent changes the chemical environment parameters by controlling pH within 1-6 and adjusting temperature to 40-80°C to optimize membrane performance. These parameter changes enhance the selective separability of the nanofiltration membrane while maintaining its long-term stability in acidic conditions, directly resolving the contradiction between separation efficiency and membrane durability
Solution Approach 2:
The invention employs a composite membrane system combining nanofiltration membrane with pretreatment (microfiltration/ultrafiltration) and post-treatment (reverse osmosis) membranes. This composite approach creates a multi-layer filtration system where each membrane type addresses specific challenges, improving both the selective separability and long-term stability of the overall separation process
2Productivity
If solvent extraction method using chelating agent is used for recovering rare metals, then recovery can be achieved, but environmental load increases and cost becomes disadvantageous
Solution Approach 1:
The patent replaces the chemical solvent extraction method with a physical membrane filtration system. Instead of using chelating agents that create environmental pollution, the invention uses nanofiltration, microfiltration, and reverse osmosis membranes to separate and recover rare metals through physical size-based filtration, thereby eliminating harmful chemical substances while maintaining high recovery efficiency
Solution Approach 2:
The membrane filtration system uses relatively inexpensive membrane materials that can be replaced periodically, replacing the expensive and environmentally harmful chelating agents. The membranes provide effective separation without creating persistent environmental contamination, making the process both economically viable and environmentally friendly
3Device complexity
If membrane filtration is used without pretreatment, then separation process is simplified, but membrane clogging occurs reducing efficiency
Solution Approach 1:
The patent implements preliminary action by adding a pretreatment step using microfiltration or ultrafiltration membranes before the main nanofiltration process. This preliminary filtration removes large particles and organics that would cause clogging, ensuring the longevity and efficiency of the subsequent nanofiltration and reverse osmosis membranes while maintaining overall process 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 method achieves stable and highly selective separation of monovalent and polyvalent rare metals, improving the efficiency and longevity of the recovery process.
Implementation Method 1
a separation step of obtaining permeated water including the monovalent rare metal and non-permeated water including the polyvalent rare metal from the rare metal-containing acidic aqueous solution by using a nanofiltration membrane
Implementation Method 2
a concentration step of obtaining non-permeated water having a higher concentration of the monovalent rare metal and permeated water having a lower concentration of the monovalent rare metal than that of the permeated water in the separation step, by using a reverse osmosis membrane
Implementation Method 3
with pretreatment steps involving microfiltration or ultrafiltration to prevent membrane clogging
Implementation Method 4
with pretreatment steps involving microfiltration or ultrafiltration to prevent membrane clogging
Data Source
AI summary
The present invention relates to a method for recovering a rare metal salt, the method including: an acid treatment step of obtaining a rare metal-containing acidic aqueous solution by bringing a material including a monovalent rare metal and a polyvalent rare metal into contact with an acidic aqueous solution; a separation step of obtaining permeated water including the monovalent rare metal and non-permeated water including the polyvalent rare metal from the rare metal-containing acidic aqueous solution by using a nanofiltration membrane satisfying the condition (1); and a concentration step of obtaining non-permeated water having a higher concentration of the monovalent rare metal and permeated water having a lower concentration of the monovalent rare metal than that of the permeated water in the separation step, by using a reverse osmosis membrane.