Perchlorate adsorption onto epichlorohydrin crosslinked chitosan hydrogel beads

Area of Science:

• Environmental Science
• Materials Science
• Chemistry

Background:

• Perchlorate (ClO4-) is an emerging water contaminant impacting thyroid function.
• Chitosan hydrogel beads (CSBs) are promising, eco-friendly adsorbents but often have low perchlorate adsorption capacity.
• Improving CSB performance for perchlorate removal is crucial for water safety.

Purpose of the Study:

• To synthesize and characterize epichlorohydrin crosslinked chitosan hydrogel beads (ECH-CSBs).
• To evaluate the adsorption and desorption performance of ECH-CSBs for perchlorate removal from water.
• To investigate the adsorption mechanism and kinetics of perchlorate onto ECH-CSBs.

Main Methods:

• Synthesis and characterization of ECH-CSBs.
• Batch adsorption experiments to determine adsorption capacity, isotherm, and kinetics.
• X-ray photoelectron spectroscopy (XPS) and Density Functional Theory (DFT) calculations to elucidate adsorption mechanisms.
• Desorption and regeneration studies.

Main Results:

• ECH-CSBs exhibit a point of zero charge at pH 5.1.
• High perchlorate adsorption capacity (63.4–76.3 mg/g) achieved between pH 4.0-10.0 at 303.15 K, following Langmuir isotherm.
• Adsorption follows pseudo-first-order kinetics, limited by intra-particle diffusion.
• ECH crosslinking enhances hydrophilicity and perchlorate adsorption.
• Complete regeneration and 100% adsorption capacity recovery over 12 cycles using 0.1 M NaOH.

Conclusions:

• ECH-CSBs are effective and reusable adsorbents for perchlorate removal.
• Electrostatic interactions between protonated amine groups and perchlorate drive adsorption.
• Interference from common anions (HCO3-, SO42-) necessitates pre-treatment for natural water applications.
• The developed ECH-CSBs show significant potential for practical water treatment.