Precipitation-Dissolution Switchable Surfactant-Based Microemulsions: Fabrication and Potential Applications in...

Area of Science:

• Environmental Chemistry
• Colloid and Surface Chemistry

Background:

• Surfactant-enhanced soil washing (SESW) faces challenges in postprocessing, including efficient solubilizate release and surfactant recycling.
• Microemulsions are effective extractants but require effective demulsification and recovery methods.

Purpose of the Study:

• To develop a precipitation-dissolution switchable surfactant for efficient microemulsion demulsification and surfactant recycling in SESW.
• To evaluate the performance of DSeNa-based microemulsions for the removal of p-nitrochlorobenzene (pNCB) from soil.

Main Methods:

• Preparation of DSeNa-based microemulsions using the phase diagram approach.
• Demulsification of microemulsions via acidification with HCl to precipitate dodecyl seleninic acid (DSeH).
• Filtration for DSeH recovery and regeneration into DSeNa; pNCB extraction and separation; aqueous phase treatment.

Main Results:

• DSeNa-based microemulsions were rapidly and efficiently demulsified into a three-phase system (DSeH, oil, aqueous) upon acidification.
• Over 96.5% of DSeH was recycled with near 100% purity and easily regenerated into DSeNa.
• Up to 99.9% pNCB removal from soil was achieved, with 99.9% of pNCB separated into the oil phase and the aqueous phase's COD reduced to 7.8 mg O2 L-1.

Conclusions:

• DSeNa is a highly effective switchable surfactant for SESW, enabling efficient demulsification and high recovery rates.
• The developed method facilitates the recycling of surfactants and effective separation of pollutants, offering a sustainable approach for soil remediation.