Highly Regenerable Magnetic Sulfonated Chitosan Crosslinked with Glutaraldehyde Composite beads (Iron sand/NaSO3-Chi-G) for Aqueous Mercury Removal

We developed a novel adsorbent from sulfonated, glutaraldehyde-crosslinked chitosan embedded with magnetic iron sand. The adsorbent was synthesized through a two-step process: (1) sulfonation with N(SO₃Na)₃ to introduce sulfonate groups, and (2) crosslinking with glutaraldehyde to enhance structural stability. The optimal formulation, containing 43.5% iron sand and crosslinked with 0.17 M glutaraldehyde, exhibited the highest Hg²⁺ adsorption capacity (30.74 mg/g) at pH 3. The adsorbents were characterized using Scanning Electron Microscopy (SEM), Fourier transform infra-red spectroscopic (FT-IR), and X-ray diffraction (XRD) techniques. Adsorption equilibrium was achieved within 60 minutes, and isotherm modeling showed that the process followed the Freundlich model (R² = 0.98). The adsorbent demonstrated excellent reusability, maintaining its Hg²⁺ adsorption capacity (49.98 ± 0.06 mg/g initially to 49.82 ± 0.02 mg/g after five cycles). Additionally, it effectively removed nearly 100% of mercury from real contaminated water samples. In conclusion, magnetic sulfonated chitosan crosslinked with glutaraldehyde is a highly effective solution for mercury remediation in practical applications.