A Method for Seawater Desalination via Squeezing Ionic Hydrogels

Area of Science:

• Materials Science
• Chemical Engineering
• Environmental Science

Background:

• Seawater desalination is crucial for addressing global water scarcity.
• Conventional methods like reverse osmosis (RO) and multistage flash distillation (MSF) are energy-intensive.
• Hydrogel-based desalination offers a potential low-energy alternative.

Purpose of the Study:

• To investigate the use of poly(sodium acrylate-co-2-hydroxyethyl methacrylate) hydrogels for freshwater production from seawater.
• To enhance salt rejection and water recovery by incorporating sodium acrylate (SA).
• To analyze the hydrogel's structural properties and reusability for desalination.

Main Methods:

• Fabrication of poly(sodium acrylate-co-2-hydroxyethyl methacrylate) hydrogels with varying SA concentrations.
• Application of mechanical force to squeeze hydrogels for water extraction.
• Measurement of salt rejection and water recovery rates.
• Analysis of hydrogel pore size distribution using mercury intrusion porosimetry.
• Evaluation of hydrogel performance after multiple reuse cycles.

Main Results:

• Incorporating SA significantly improved salt rejection from 27.62% to 64.57% at 35.00g/L NaCl.
• Optimal SA concentration was identified, as higher concentrations led to decreased salt rejection due to structural changes.
• Water recovery increased with higher swelling degrees.
• The SA5/HEMA15 hydrogel exhibited a multi-pore structure, potentially benefiting desalination.
• The hydrogel maintained good desalination performance after four reuse cycles.

Conclusions:

• The developed hydrogels show potential for efficient seawater desalination and freshwater production.
• While salt rejection is lower than RO, MSF, and MED, hydrogels can serve as a pre-treatment to reduce energy consumption.
• This approach offers a promising, low-energy pathway for forward osmosis and reverse osmosis pre-treatment.