Emulsion stabilization using ionic liquid [BMIM]+[NTf2]- and performance evaluation on the extraction of chromium

Area of Science:

• Chemical Engineering
• Separation Science
• Materials Science

Background:

• Emulsion liquid membranes (ELMs) are effective for separating and extracting chemical species.
• Achieving long-term stability in ELMs is crucial for practical applications.
• Ionic liquids offer unique properties for modifying membrane performance.

Purpose of the Study:

• To investigate the stabilizing role of the hydrophobic ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([BMIM](+)[NTf(2)](-)) in ELM preparation.
• To evaluate the impact of [BMIM](+)[NTf(2)](-) concentration on ELM stability.
• To assess the chromium (Cr) removal efficiency using the stabilized ELM.

Main Methods:

• Preparation of ELM using kerosene as solvent, Span 80 as surfactant, NaOH as internal phase, and tri-n-octylmethylammonium chloride (TOMAC) as carrier.
• Incorporation of [BMIM](+)[NTf(2)](-) as a stabilizer in the ELM.
• Stability testing of the ELM by monitoring interface height over time.
• Extraction experiments for Cr removal after a defined holding period.

Main Results:

• [BMIM](+)[NTf(2)](-) acts as a highly effective stabilizer for the ELM, extending stability from 7 minutes to approximately 7 hours at an optimal concentration of 3% (w/w).
• ELM stability increases with [BMIM](+)[NTf(2)](-) concentration up to 3% (w/w), after which higher concentrations lead to reduced stability.
• The stabilized ELM achieved an approximate 80% removal efficiency for chromium (Cr).

Conclusions:

• Hydrophobic ionic liquids, specifically [BMIM](+)[NTf(2)](-), can significantly improve the operational stability of ELMs.
• The concentration of the ionic liquid stabilizer is critical for optimizing ELM performance.
• The developed ELM shows promise for efficient heavy metal removal, such as chromium.