Separating Rare Earth Metal Oxalates via Solubility

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Solution Overview

Problem

Current methods for separating and purifying rare earth metals are complex, costly, and environmentally hazardous, particularly due to the use of organophosphorus compounds, and fail to efficiently separate lighter from heavier rare earth elements and transition metal impurities.

Innovation Solution

A selective chemical separation and purification method using an aqueous solution of oxalic acid and an organic base, such as 1-methylimidazole, to differentiate the solubility of rare earth metal oxalates, allowing for the separation of light and heavy rare earth oxalates and the removal of transition metal impurities in a single, cost-effective, and environmentally friendly step.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If solvent extraction with organophosphorus compounds is used, then rare earth metals can be separated and purified, but the process becomes complex and hazardous chemicals are used

Engineering Contradiction:

Improveseparation and purification of rare earth metalsVSAvoidcomplexity of the process

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent changes the chemical parameters of the extraction system by replacing organophosphorus compounds with carboxylic acid extractants (such as oxalic acid, malonic acid, succinic acid). This parameter change simplifies the process while maintaining separation effectiveness, directly addressing the contradiction between purification quality and process complexity

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs readily available, inexpensive carboxylic acids as extractants instead of expensive and hazardous organophosphorus compounds. These simpler chemicals can be easily handled and disposed of, reducing both process complexity and safety concerns while achieving the same separation function

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

2Manufacturing precision

If solvent extraction with organophosphorus compounds is used, then rare earth metals can be separated, but hazardous chemicals are used

Engineering Contradiction:

Improveseparation of rare earth metalsVSAvoiduse of hazardous chemicals

Core Design Contradiction:

Manufacturing precisionVSObject-affected harmful factors

Solution Approach 1:

The patent substitutes hazardous organophosphorus compounds with safe, biodegradable carboxylic acids (oxalic acid, malonic acid, succinic acid). These replacement chemicals are non-toxic, environmentally friendly, and can be easily disposed of, eliminating the harmful factors while preserving the separation capability

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The patent converts the previously harmful organophosphorus extraction system into a beneficial green chemistry system by using carboxylic acids that are inherently safe. The same extraction function is achieved but with chemicals that provide environmental benefits rather than hazards

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Manufacturing precision

If repeated fractional crystallization is used, then rare earth metals can be separated, but the process becomes time-consuming

Engineering Contradiction:

Improveseparation of rare earth metalsVSAvoidtime-consuming process

Core Design Contradiction:

Manufacturing precisionVSLoss of time

Solution Approach 1:

The patent extracts the separation function from the time-consuming repeated crystallization process by using selective chemical extraction with carboxylic acids. The extractants selectively bind to different rare earth metals, allowing separation in a single or few steps rather than requiring thousands of crystallization cycles

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent replaces the mechanical crystallization process with a chemical extraction system. Instead of relying on physical crystallization cycles, the method uses chemical complexation reactions between carboxylic acids and rare earth metals, which proceed rapidly and achieve separation in much less time

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical 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 method enables efficient separation and purification of rare earth metal oxalates in a fast, one-step process, reducing costs and environmental impact by using a water-based system, achieving high purity levels (>98%) without requiring special equipment or hazardous chemicals.

Implementation Method 1

mixing the different metal oxalates and an aqueous solution comprising oxalic acid and an organic base wherein one metal oxalate is insoluble and another metal oxalate is soluble in the aqueous solution

Methodology Applied

Scientific EffectSolubility difference: Solvation

Data Source

PatentUS11090579B2Separating rare earth metal oxalates

Publication Date: 2021.08.17 IOWA STATE UNIV RES FOUND INC

AI summary

A method is provided for separating and/or purifying different metal oxalates by mixing the different metal oxalates in an aqueous solution comprising oxalic acid and an organic base so that at least one metal oxalate is soluble and at least another metal oxalate is not soluble. Different rare earth metal oxalates and/or transition metal oxalates can be separated.