Magnetic cellulose from Cedrus deodara sawdust for Cd(II) removal: synthesis, characterization, and adsorption performance

Cadmium (Cd2+) contamination in aquatic systems poses serious environmental and public health risks, necessitating sustainable and easily recoverable adsorbents. In this study, cellulose was extracted from Cedrus deodara sawdust and magnetically modified through Fe2+/Fe3+ co-precipitation to synthesize a magnetic cellulose adsorbent for Cd2+ removal from aqueous solutions. The materials were characterized using Fourier transform infrared spectroscopy, X-ray diffraction, dynamic light scattering, scanning electron microscopy, energy-dispersive spectroscopy, and nuclear magnetic resonance to confirm cellulose structure, iron oxide incorporation, particle size and stability, surface morphology, elemental composition, and purity. Batch adsorption experiments assessed the effects of contact time, initial Cd2+ concentration, pH, adsorbent dose, and temperature, while residual Cd2+ concentrations were determined by atomic absorption spectrophotometry (AAS). Adsorption capacity increased with contact time and initial Cd2+ concentration, reaching 488.9 mg g−1 after 60 min at 100 mg L−1. At higher concentrations (up to 120 mg L−1), calculated capacities increased based on mass-balance relationships under the applied conditions. Cd(II) adsorption was favored under alkaline pH and elevated temperatures. Recyclability tests demonstrated stable performance over three cycles with 89% Cd(II) removal. Kinetic data were best described by pseudo-first-order and Ritchie second-order models (R2 > 0.99), suggesting diffusion-controlled uptake followed by surface interactions. Equilibrium data fitted the Redlich–Peterson isotherm better than the Langmuir model, indicating heterogeneous surface energies and possible multilayer adsorption. Overall, magnetically modified sawdust-derived cellulose shows promising laboratory-scale performance for Cd2+ removal, warranting further evaluation in complex wastewater systems.