Acid-resistant ion-pair amphiphile for pH-switchable emulsion liquid membranes

Area of Science:

• Materials Science
• Environmental Science
• Chemical Engineering

Background:

• Emulsion liquid membranes (ELMs) are vital for separation technologies and wastewater treatment.
• Stabilizing ELMs typically requires high surfactant concentrations, posing challenges for efficient and rapid demulsification.
• Current demulsification methods often involve energy-intensive processes like heating or centrifugation.

Purpose of the Study:

• To develop a pH-responsive ELM system for efficient metal ion extraction and facile demulsification.
• To investigate the performance of a novel ion-pair amphiphile, hexadecyldimethylammonium dodecylbenzenesulfonate (C16DMA-DBSA), in ELM applications.
• To establish a low-energy, sustainable separation method for wastewater treatment.

Main Methods:

• Fabrication of a water-in-oil-in-water (W/O/W) ELM system utilizing the pH-responsive ion-pair amphiphile C16DMA-DBSA.
• Extraction of various metal ions (Cd(II), Pb(II), Cu(II), Mn(II)) from aqueous solutions using the developed ELM.
• Investigation of pH-triggered demulsification for phase separation and recovery of the oil phase.
• Evaluation of the ELM system's reusability and operational stability over multiple cycles.

Main Results:

• The C16DMA-DBSA based ELM demonstrated superior emulsifying performance in acidic media and stabilized diverse emulsion types (O/W, O/W/O, W/O) via pH control.
• Achieved outstanding Cd(II) extraction efficiency of 98.29% within 4 minutes using a W/O/W ELM with an acidic internal phase.
• Facilitated efficient phase separation under mild conditions through pH-triggered demulsification, eliminating the need for conventional harsh methods.
• The recovered oil phase was successfully reused for five cycles with sustained high Cd(II) extraction efficiency (90.62%), showcasing excellent recyclability and stability.

Conclusions:

• The developed pH-responsive ELM system offers a low-energy and efficient strategy for metal ion removal from wastewater.
• The switchable ion-pair surfactant C16DMA-DBSA provides a novel approach for designing stable yet easily demulsifiable ELMs.
• This research presents a sustainable and operationally stable solution for advanced separation technologies and environmental remediation.