Mercury(II) removal with modified magnetic chitosan adsorbents

Area of Science:

• Materials Science
• Environmental Chemistry
• Nanotechnology

Background:

• Mercury (Hg(II)) contamination in aqueous solutions poses significant environmental and health risks.
• Chitosan, a biopolymer, is a promising material for heavy metal removal due to its functional groups.
• Development of efficient and reusable adsorbents is crucial for environmental remediation.

Purpose of the Study:

• To synthesize and characterize two modified chitosan adsorbents for Hg(II) removal.
• To compare the adsorption performance of a standard chitosan (CS) and a magnetic chitosan (CSm) derivative.
• To investigate the adsorption mechanism, kinetics, thermodynamics, and reusability of the developed adsorbents.

Main Methods:

• Synthesis of chitosan cross-linked with glutaraldehyde (CS) and magnetic chitosan (CSm) functionalized with Fe₃O₄ nanoparticles.
• Characterization using SEM/EDAX, FTIR, XRD, DTG, DTA, and VSM.
• Adsorption studies involving varying pH, contact time, temperature, and thermodynamic analysis.
• Evaluation of adsorption capacity using Langmuir and Freundlich models and assessment of adsorbent reusability.

Main Results:

• Both CS and CSm effectively removed Hg(II) from aqueous solutions.
• The optimal pH for adsorption was 5, and for desorption was 2.
• Adsorption kinetics followed pseudo-first, pseudo-second order, and Elovich models.
• Maximum adsorption capacities at 25 °C were 145 mg/g for CS and 152 mg/g for CSm.
• Thermodynamic analysis indicated spontaneous and endothermic adsorption.
• Adsorbents demonstrated good reusability over multiple adsorption-desorption cycles.

Conclusions:

• Modified chitosan derivatives, particularly the magnetic version (CSm), are effective adsorbents for Hg(II) removal.
• The magnetic property of CSm facilitates easier separation and potential for reuse.
• These adsorbents show promise for practical applications in wastewater treatment for mercury remediation.