An Extremely Salt-Resistant Hydrogel-Based Solar Evaporator for Stable Saturated Brine Desalination

Area of Science:

• Materials Science
• Chemical Engineering
• Environmental Science

Background:

• Hydrogel solar evaporators offer efficient water evaporation via reduced enthalpy.
• A key challenge is balancing high evaporation rates with salt tolerance.
• Existing systems struggle with salt accumulation and reduced performance in saline conditions.

Purpose of the Study:

• To design and fabricate a 3D chitosan-based hydrogel evaporator with enhanced salt resistance and high evaporation rates.
• To address the trade-off between evaporation efficiency and durability in high-salinity environments.
• To improve the practicality of hydrogel evaporators for large-scale desalination applications.

Main Methods:

• A one-pot in situ strategy and directional freezing method were employed to create a 3D chitosan hydrogel.
• The hydrogel featured a directional vertical channel structure to facilitate salt ion return and steam escape.
• Performance was evaluated under one sun illumination using saturated brine (26.47 wt.% salinity).

Main Results:

• The designed hydrogel evaporator achieved an excellent evaporation rate of 2.83 kg m^-2 h^-1.
• Exceptional salt resistance was demonstrated, with no salt crystal accumulation after 8 hours of continuous operation in saturated brine.
• The vertical channel structure enabled efficient salt ion management and unimpeded steam overflow.

Conclusions:

• The novel 3D chitosan hydrogel evaporator overcomes the limitations of traditional systems by achieving both high evaporation rates and superior salt resistance.
• This work presents a record-high salt resistance for hydrogel-based evaporation systems.
• The developed technology significantly enhances the applicability of hydrogel evaporators for effective high-salinity water desalination.