Zero Liquid Discharge of Ultrahigh-Salinity Brines with Temperature Swing Solvent Extraction

Area of Science:

• Environmental Science
• Chemical Engineering
• Water Treatment Technologies

Background:

• Achieving zero liquid discharge (ZLD) for hypersaline brines presents significant technical and energy challenges.
• Current methods like thermal evaporation are energy-intensive and may not be fully sustainable.

Purpose of the Study:

• To demonstrate the efficacy of temperature swing solvent extraction (TSSE) for ZLD of ultrahigh-salinity brines.
• To evaluate TSSE as a sustainable, membrane-less, and nonevaporative desalination technology.

Main Methods:

• Utilized temperature swing solvent extraction (TSSE) with a low-polarity solvent (diisopropylamine) to extract water from hypersaline brine.
• Simulated hypersaline feed using 5.0 M NaCl solution (≈292 g/L TDS).
• Tested TSSE on actual irrigation drainage water concentrate to assess field applicability.

Main Results:

• Achieved complete water extraction from simulated hypersaline brine.
• Recovered product water with <5% of the original NaCl concentration.
• Precipitated nearly all salt as mineral solid waste.
• Demonstrated consistent ZLD performance and solvent recyclability over three cycles.
• Successfully applied TSSE to an irrigation drainage water concentrate.

Conclusions:

• TSSE is a viable technology for achieving zero liquid discharge of ultrahigh-salinity brines.
• The membrane-less and nonevaporative nature of TSSE offers a more sustainable alternative to thermal evaporation.
• TSSE shows practical applicability for real-world industrial and agricultural wastewater treatment.