Highly Effective Covalently Crosslinked Composite Alginate Cryogels for Cationic Dye Removal

Area of Science:

• Materials Science
• Environmental Science
• Polymer Chemistry

Background:

• Macroporous hydrogels are gaining traction for wastewater treatment applications.
• Alginate, a natural polymer, is recognized for its sustainable properties and effectiveness in removing cationic dyes.
• Methylene blue (MB) is a common cationic dye pollutant.

Purpose of the Study:

• To synthesize alginate/montmorillonite composite macroporous hydrogels (cryogels) using a one-step cryogelation technique.
• To evaluate the structural, mechanical, and adsorption properties of the synthesized cryogels for MB removal.
• To investigate the adsorption mechanism and kinetics of MB onto the alginate/montmorillonite cryogels.

Main Methods:

• Synthesis of alginate/montmorillonite composite cryogels via cryogelation and carbodiimide cross-linking.
• Characterization using FT-IR, SEM, gel fraction, swelling, and uniaxial compression tests.
• Methylene blue adsorption experiments to determine adsorption capacity and kinetics.

Main Results:

• The cryogels exhibited high gelation yield (up to 80%), significant porosity, and excellent mechanical elasticity.
• The alginate/montmorillonite cryogels demonstrated a high MB adsorption capacity of 559.94 mg g⁻¹.
• Adsorption kinetics followed the Pseudo-Second-Order model, indicating chemisorption as the rate-limiting step.
• Effective dye removal efficiency reached 93.7%.

Conclusions:

• Alginate/montmorillonite composite cryogels are highly effective adsorbents for methylene blue removal.
• The cryogels' enhanced porosity and mechanical properties contribute to their superior dye adsorption capacity.
• These materials present a viable and sustainable alternative for wastewater treatment compared to existing alginate/montmorillonite adsorbents.