Bifunctional Extractant for Rare Earth Separation from Phosphoric Acid
Solution Overview
Problem
Current extractants for rare earths from aqueous phosphoric acid solutions are inefficient in extracting both light and heavy rare earths with high selectivity over metal impurities like iron, especially at varying phosphoric acid concentrations, limiting their industrial applicability.
Innovation Solution
A novel extractant comprising bifunctional compounds with an amide and phosphonic or phosphonate function, combined with anionic or non-ionic surfactants, which forms a synergistic mixture for efficient extraction of rare earths from aqueous phosphoric acid solutions, regardless of phosphoric acid concentration, using liquid-liquid extraction techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional extractants (DEHPA, OPPA, MOPPA/DOPPA mixtures) are used for rare earth extraction from aqueous phosphoric acid solutions, then extraction of heavy rare earths can be achieved, but light rare earths are not extracted efficiently and selectivity over iron impurities is poor
Solution Approach 1:
The invention uses a composite extractant system combining a phosphonic acid derivative (with specific molecular structure containing P=O and P-OH groups) with a surfactant (anionic or non-ionic). This composite approach creates synergistic effects where the phosphonic acid component provides selective binding to rare earth ions while the surfactant component enhances solubility and extraction efficiency in phosphoric acid media, achieving both high extraction yields and selectivity over iron impurities
Solution Approach 2:
The invention optimizes specific parameters including the phosphonic acid derivative structure (with R1-R6 hydrocarbon groups having specific carbon chain lengths), the ratio of extractant components, and pH conditions. By carefully controlling these parameters, the extractant achieves maximum selectivity for rare earths over iron while maintaining high extraction efficiency for both light and heavy rare earths across varying phosphoric acid concentrations
2Reliability
If extractants with strong affinity for iron are used to improve selectivity, then iron removal is enhanced, but extraction yields of rare earths decrease
Solution Approach 1:
The phosphonic acid derivative exhibits local quality in its molecular structure with specific functional groups (P=O, P-OH) that create distinct binding sites. The hydrocarbon chains (R1-R6 groups with specific carbon lengths) provide hydrophobic regions that interact with the surfactant, while the phosphonic acid groups provide selective coordination to rare earth ions. This localized functional differentiation enables selective rare earth extraction while rejecting iron
3Quantity of substance
If extraction conditions are optimized for high rare earth recovery, then extraction yield improves, but the process becomes sensitive to phosphoric acid concentration variations
Solution Approach 1:
The extractant system exhibits universal performance across varying phosphoric acid concentrations (from 10% to 80% P2O5). The phosphonic acid derivative combined with surfactant creates a multi-functional system that maintains effective rare earth extraction under diverse acid concentration conditions, making the process adaptable to different feedstock compositions and operational conditions without requiring reoptimization
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 novel extractant achieves high extraction yields and selectivity for both light and heavy rare earths over metal impurities, including iron, across a broad range of phosphoric acid concentrations, enhancing the efficiency and scalability of rare earth recovery processes.
Implementation Method 1
using liquid-liquid extraction techniques
Data Source
AI summary
An extractant which makes it possible to extract both light rare earths and heavy rare earths from an aqueous phosphoric acid solution, likely to be present in this solution, and which is characterised in that it comprises: a compound of formula (I) below:wherein R1 and R2, identical or different, are a hydrocarbon group, saturated or unsaturated, linear or branched, in C6 to C12; R3 is a hydrocarbon group, in C1 to C6, or a hydrocarbon group, saturated or unsaturated, monocyclic, in C3 to C8; R4 and R5, identical or different, are a hydrogen atom or a hydrocarbonate group, saturated or unsaturated, linear or branched, in C2 to C8; and a surfactant. Applications of this extractant include treatment of aqueous solutions from the leaching of natural phosphates by sulphuric acid and aqueous solutions from the leaching of urban minerals by phosphoric acid, in view of making profitable use of the rare earths present in these solutions.