Superhydrated Zwitterionic Hydrogel with Dedicated Water Channels Enables Nonfouling Solar Desalination

Area of Science:

• Materials Science
• Environmental Science
• Chemical Engineering

Background:

• Solar-driven interfacial desalination (SID) is a sustainable freshwater source but faces challenges like salt crystallization and biofouling.
• Existing zwitterionic hydrogel solar evaporators lack sufficient hydration and are vulnerable to salt, limiting their real-world application.

Purpose of the Study:

• To develop a superhydrated, zwitterionic hydrogel solar evaporator inspired by marine organisms for efficient, durable, and nonfouling SID.
• To overcome the limitations of current hydrogel-based solar evaporators in complex marine conditions.

Main Methods:

• Fabrication of a zwitterionic poly(trimethylamine N-oxide, PTMAO)/polyacrylamide (PAAm)/polypyrrole (PPy) hydrogel (PTAP).
• Characterization of PTAP's hydration, water transport, mechanical strength, and photothermal properties.
• Evaluation of PTAP's desalination performance, long-term stability, and resistance to various foulants (proteins, bacteria, algae) under simulated solar irradiation.
• Utilizing molecular dynamics simulations to understand the hydrogel's nonfouling mechanism.

Main Results:

• PTAP exhibits a high evaporation rate of 2.35 kg m⁻² h⁻¹ under 1 kW m⁻² in 10 wt% NaCl solution.
• The hydrogel maintained stable operation for over 100 hours without salt accumulation.
• PTAP demonstrated excellent resistance to protein, bacterial, and algal adhesion, confirming its nonfouling capabilities.
• Molecular dynamics simulations confirmed that the robust hydration shell contributes to the nonfouling properties.

Conclusions:

• The developed superhydrated zwitterionic hydrogel (PTAP) offers a promising solution for efficient, durable, and nonfouling solar-driven interfacial desalination.
• PTAP's unique structure and properties enable sustainable freshwater production from saline water, even in challenging marine environments.
• This research advances the design of next-generation solar evaporators for practical desalination applications.