Development and optimization of high-performance extraction chromatography method for separation of rare earth...

Area of Science:

• Analytical Chemistry
• Separation Science
• Materials Science

Background:

• Chromatographic separation is crucial for rare earth element (REE) analysis.
• Common extractants like tributyl phosphate (TBP), di-(2-ethylhexyl) phosphoric acid (HDEHP), and Aliquat-336 are used for REE separation.
• Optimizing separation efficiency and speed is essential for practical applications.

Purpose of the Study:

• To compare the effectiveness of TBP, HDEHP, and Aliquat-336 for chromatographic separation of REEs.
• To optimize the HDEHP-based extraction chromatographic method for complete REE series separation.
• To investigate the impact of temperature and flow rate on separation efficiency.

Main Methods:

• Columns were prepared with TBP, HDEHP, and Aliquat-336, using mineral acid as eluent.
• Retention factors and separation resolution (Rs) were determined for each extractant.
• HDEHP-coated columns were used to optimize separation using stepwise gradient elution, varying temperature and flow rate.

Main Results:

• HDEHP exhibited the highest separation efficiency (mean Rs = 2.76), followed by TBP (mean Rs = 1.52) and Aliquat-336 (mean Rs = 1.42).
• Optimized HDEHP extraction with stepwise gradient elution achieved complete separation of the entire REE series within 25 minutes.
• Higher column temperatures and a flow rate of 1.5 mL/min improved light REE separation, with plate heights (H) ranging from 0.011 to 0.027 mm.

Conclusions:

• HDEHP is the most effective extractant for chromatographic separation of the entire REE series.
• Stepwise gradient elution, optimized temperature, and flow rate significantly enhance REE separation efficiency and speed.
• The developed HDEHP method provides rapid and complete separation of REEs, valuable for analytical and industrial purposes.