Magnetic chitosan kaolinite cellulose nanofibril cryogel beads for efficient removal of methylene blue from water
Eman Fayad, Maha Alsunbul, Reem S. Alazragi, A. Ebada, Hafiz Saqib Ali, Mahmoud F. Mubarak
Abstract
Using a green freeze gelation and genipin crosslinking technique, chitosan (C), kaolinite (K), cellulose nanofibrils (CNF), and Fe 3 O 4 nanoparticles were combined to create CK–CNF–Fe cryogel beads, a novel magnetic composite. Freeze gelation was used to create the beads, which were then cross linked using genipin, a non-toxic natural cross linker, and Fe 3 O 4 nanoparticles were included in situ. The addition of genipin guarantees the material’s safe application in wastewater treatment while also enhancing its eco-friendliness. With an average pore width of about 11 μm, an average bead diameter of 1.7 mm, and a specific surface area of 230 m² g⁻¹, the beads displayed a macroporous three dimensional structure. The maximum adsorption capacity was 812 mg g⁻¹ at pH 7 and 298 K in batch adsorption studies using Methylene Blue (MB, 150 mg L⁻¹), which fit the Langmuir isotherm model (R² > 0.995). 95% equilibrium absorption was reached in 22 min, and adsorption proceeded according to pseudo second order kinetics (k₂ = 0.016 g mg⁻¹ min⁻¹). Using a 0.3 T magnet, the beads’ great magnetic responsiveness (saturation magnetization, Mₛ = 20 emu g⁻¹) allowed for > 99% recovery in less than 35 s. >90% dye desorption during regeneration at pH 2 was made possible by the pH-responsive swelling behavior, which ranged from 500% (pH 3) to 880% (pH 10). Surprisingly, after six adsorption desorption cycles, the beads retained more than 90% of their adsorption effectiveness. These results highlight CK–CNF–Fe cryogel beads as eco-friendly, high performance, and magnetically retrievable adsorbents with excellent reusability for sustainable wastewater treatment.