Surfactant-modified chitosan beads for cadmium ion adsorption

Area of Science:

• Environmental Science
• Materials Science
• Chemistry

Background:

• Cadmium (Cd2+) is a highly toxic heavy metal, posing significant environmental and health risks due to its carcinogenic and teratogenic properties.
• Effective removal of cadmium ions from aqueous environments is crucial for public health and ecological safety.

Purpose of the Study:

• To develop and characterize novel surfactant-modified chitosan (SMCS) beads for enhanced cadmium ion removal.
• To investigate the adsorption kinetics and isotherm behavior of SMCS beads for Cd2+ removal.

Main Methods:

• Chitosan (CS) beads were modified with sodium dodecyl sulfate (SDS) to form surfactant bilayers on the CS surface, creating SMCS beads.
• Characterization of SMCS beads using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD).
• Batch adsorption experiments were conducted to evaluate Cd2+ removal efficiency and capacity under varying conditions.

Main Results:

• SMCS beads demonstrated a significantly higher adsorption capacity for Cd2+ (up to 125 mg/g) compared to unmodified CS beads (three times higher).
• The adsorption process followed a pseudo-second-order kinetic model, indicating chemisorption as the rate-limiting step.
• Adsorption isotherm data best fitted the Langmuir model, suggesting monolayer adsorption onto homogeneous SMCS surfaces.
• High removal efficiency (nearly 100%) was achieved at lower Cd2+ concentrations (10-30 mg/L) with a dosage of 0.45 g/L SMCS within 10 hours.

Conclusions:

• Surfactant modification of chitosan beads with SDS is a highly effective strategy for enhancing cadmium ion adsorption.
• SMCS beads present a superior adsorbent material for the remediation of cadmium-contaminated water.
• The Langmuir model and pseudo-second-order kinetics provide a good description of the cadmium adsorption process onto SMCS beads.