Preconcentration of Superbase Ionic Liquid from Aqueous Solution by Membrane Filtration

Area of Science:

• Materials Science
• Chemical Engineering
• Separation Science

Background:

• Organic superbase ionic liquids (ILs) enable high-quality cellulose dissolution and fiber regeneration for textiles.
• Efficient recovery and purification of ILs from spinning baths are critical for process economic viability but remain underexplored.

Purpose of the Study:

• To investigate pressure-driven membrane processes for separating and recycling ionic liquids from aqueous solutions.
• To evaluate the performance of different membrane types and operating conditions for IL recovery.

Main Methods:

• Tested microfiltration, ultrafiltration, nanofiltration, and reverse osmosis membranes for IL recovery.
• Investigated the effects of pressure, IL concentration, temperature, and multi-cycle operation.
• Analyzed the retention and volumetric flux of two specific superbase ILs: [mTBDH][OAc] and [mTBNH][OAc].

Main Results:

• Nanofiltration and reverse osmosis membranes (NF270-NF, BW30LE-RO) achieved significant IL retentions (>45%).
• Increased pressure and temperature enhanced volumetric flux but reduced IL retention.
• Higher IL concentrations decreased volumetric flow and rejection.
• Serial filtration achieved a three-fold increase in IL concentration, reaching up to 14 wt %.

Conclusions:

• Membrane filtration is an effective method for preconcentrating ILs from dilute solutions.
• Nanofiltration and RO show promise for IL recovery in textile spinning processes.
• Optimizing operating parameters is key to maximizing IL recovery efficiency and economic feasibility.