Cloud point extraction: an alternative to traditional liquid-liquid extraction for lanthanides(III) separation

Area of Science:

• Analytical Chemistry
• Separation Science
• Materials Chemistry

Background:

• Lanthanum(III) and Gadolinium(III) are critical rare earth elements with similar chemical properties, posing challenges for separation.
• Efficient separation techniques are vital for purifying and utilizing these elements in various technological applications.

Purpose of the Study:

• To develop and optimize a Cloud Point Extraction (CPE) method for selective separation of lanthanum(III) and gadolinium(III) nitrates.
• To investigate the influence of non-ionic surfactant structure and chelating agent-metal molar ratio on extraction efficiency and selectivity.

Main Methods:

• Cloud Point Extraction (CPE) utilizing the formation of lanthanide(III)-8-hydroxyquinoline (8-HQ) complexes.
• Complexes are solubilized in a micellar phase of non-ionic surfactant (Triton X-114) and extracted above the cloud point temperature (CPT).
• Optimization of surfactant type and chelating agent-metal molar ratio for enhanced separation.

Main Results:

• High extraction efficiency for Gadolinium(III) (up to 96%) achieved from equimolar La(III)/Gd(III) solutions.
• Excellent selectivity for Gd(III) over La(III) (Gd(III)/La(III) selectivity > 30) demonstrated using Triton X-114.
• A significant Gadolinium(III) decontamination factor of 50 was obtained under optimal conditions.

Conclusions:

• Cloud Point Extraction (CPE) offers a highly efficient and selective method for separating La(III) and Gd(III) nitrates.
• The choice of non-ionic surfactant and chelating agent-metal ratio are critical parameters for optimizing separation performance.
• This technique shows promise for the purification and recovery of valuable rare earth elements.