Dual Physically Crosslinked Hydrogels via Multi-Dimensional Carbon Materials for Methylene Blue Adsorption

Area of Science:

• Materials Science
• Environmental Science
• Chemical Engineering

Background:

• Treating dye-laden wastewater requires high-performance adsorbents.
• Understanding structure-property relationships is crucial for adsorbent development.
• Carbon materials offer unique properties for adsorption applications.

Purpose of the Study:

• To investigate the effect of carbon material dimensionality on hydrogel adsorbent properties.
• To evaluate the methylene blue (MB) adsorption performance of SA/PAM hydrogels incorporating biochar (BC), carbon nanotubes (CNT), and graphene oxide (GO).
• To elucidate the adsorption mechanisms and cyclic stability of the composite hydrogels.

Main Methods:

• Fabrication of dual physically crosslinked sodium alginate/polyacrylamide (SA/PAM) hydrogels with varying carbon materials (0D BC, 1D CNT, 2D GO).
• Characterization of hydrogel composite structures and mechanical properties.
• Methylene blue adsorption experiments under optimized conditions (25 °C, 100 mg/L MB, pH 10-11), including isotherm, kinetic, and cyclic studies.

Main Results:

• Successful incorporation and dispersion of carbon materials, enhancing hydrogel mechanical properties.
• Maximum MB adsorption capacities achieved: 411.5 mg/g (BC-H), 410.6 mg/g (GO-H), and 422.8 mg/g (CNT-H).
• Adsorption followed Langmuir model and pseudo-second-order kinetics, indicating chemisorption.
• Real water samples reduced capacity due to competitive adsorption.
• Hydrogels retained 57.7% (BC-H), 67.2% (GO-H), and 61.7% (CNT-H) capacity after five cycles.

Conclusions:

• Carbon material dimensionality significantly influences hydrogel adsorbent performance for MB removal.
• Synergistic adsorption mechanisms include electrostatic attraction, π-π stacking, and physical entrapment.
• Physical structural changes and chemical site occupation impact cyclic stability.
• This study provides a design strategy for advanced adsorbents and theoretical basis for dye wastewater remediation.