Ice-Templated Zwitterionic Sponge Hydrogels for Stable and Efficient Solar Desalination in High-Salinity Brines

Area of Science:

• Materials Science
• Environmental Science
• Chemical Engineering

Background:

• Solar-driven steam generation (SSG) is a sustainable desalination method.
• Controlling macroporous structures in salt-tolerant hydrogels for SSG is challenging.
• Zwitterionic hydrogels offer potential for water transport and salt tolerance.

Purpose of the Study:

• To develop a temperature-regulated, salt-tolerant hydrogel for efficient solar desalination.
• To investigate the effect of carbon black coating on hydrogel performance.
• To assess the scalability and freshwater quality from the developed hydrogel system.

Main Methods:

• Fabrication of carbon black-coated PDMAPS sponge hydrogel (PDMAPS-CB-SH) using ice-templated polymerization.
• Tuning pore size and connectivity by controlling ice-crystal growth.
• Incorporation of carbon black nanoparticles for enhanced photothermal conversion.

Main Results:

• Optimized PDMAPS-CB-SH showed rapid water transport and stable swelling in up to 10 wt % NaCl brine.
• Achieved a high evaporation rate of 1.93 kg m^-2 h^-1 and 95.1% efficiency in seawater under 1 sun.
• Demonstrated stable evaporation under high salinity and scalability in outdoor field tests, yielding 12.35 kg m^-2 day^-1 freshwater.

Conclusions:

• Ice-templated zwitterionic sponge hydrogels are a versatile platform for efficient solar desalination.
• The PDMAPS-CB-SH system is effective for challenging high-salinity conditions.
• The generated freshwater meets WHO drinking-water standards, indicating practical applicability.