Salt-Induced Phase Separation in Polyampholyte Hydrogels for Stable Solar Desalination

Area of Science:

• Materials Science
• Environmental Science
• Chemical Engineering

Background:

• Solar-driven interfacial evaporation is a key technology for decentralized freshwater production.
• Conventional hydrogel evaporators face challenges like poor pore connectivity and salt-induced shrinkage, limiting their efficiency in desalination.

Purpose of the Study:

• To design and fabricate a novel polyampholyte hydrogel with enhanced structural stability and efficient water transport for solar desalination.
• To improve the evaporation rate and long-term performance of hydrogel-based solar evaporators in saline environments.

Main Methods:

• Fabrication of a polyampholyte hydrogel using high-concentration sodium sulfate to induce a salting-out effect and create an interconnected porous structure.
• Functionalization of the hydrogel with polypyrrole photothermal nanoparticles to enhance solar absorption.
• Testing the evaporator's performance under simulated solar irradiation (1.0 kW·m^-2) using real seawater.

Main Results:

• The fabricated hydrogel exhibited efficient transport channels in pure water and resisted salt-induced shrinkage in seawater due to salting-in characteristics.
• The functionalized evaporator achieved a high solar evaporation rate of approximately 2.18 kg·m^-2·h^-1.
• Stable performance was maintained without decay over seven days of continuous operation in real seawater.

Conclusions:

• The developed polyampholyte hydrogel offers a scalable and environmentally friendly design for high-performance solar desalination.
• This strategy effectively addresses limitations of conventional hydrogels, paving the way for sustainable freshwater generation.
• The study demonstrates a promising approach for tackling global freshwater scarcity through advanced materials for solar energy conversion.