New insights into residual triiodide ion removal from iodinated water using magnetic CoFe₂O₄ nanoparticles: exploring adsorption behavior and mechanisms

This study evaluates the adsorption performance of cobalt ferrite (CoFe₂O₄)–based magnetic nanoadsorbents (CF-MagNa) for the removal of triiodide ions ( \({I}_{3}^{-}\) $I_3^{-}$ ) from iodinated water. The crystalline structure and phase purity of the synthesized material were confirmed via X-ray diffraction (XRD), which determined a crystallite size of 42 nm and a specific surface area of 26.98 m²/g. Field emission scanning electron microscopy (FESEM) revealed a porous morphology conducive to enhanced adsorption. The ferromagnetic properties of CF-MagNa were characterized using vibrating sample magnetometry (VSM), which demonstrated a saturation magnetization (σ_s) of 74.98 emu/g, a remanent magnetization (σ_r) of 29.82 emu/g, and a coercivity (H_c) of 1304 Oe, significant magnetic separation potential. Batch adsorption experiments revealed a 61.6% reduction in \({I}_{3}^{-}\) $I_3^{-}$ concentration at a CF-MagNa dosage of 2 mg/mL. Adsorption isotherms were analyzed, with the Langmuir model yielding a maximum adsorption capacity (Q_max) of 13.641 mg/g and a Langmuir constant (K_L) of 0.00996 L/mg. The Freundlich model provided a capacity factor (K_F) of 1.892 mg/g and a heterogeneity factor (n_F) of 1.805 L/mg, while the Temkin model yielded a heat of adsorption (B) of 3.404 J/mol and a Temkin constant (K_T) of 0.743 L/g. The Dubinin-Radushkevich (D-R) isotherm demonstrated the highest correlation (R² = 0.97), with a maximum adsorption capacity of 8.28 mg/g. These results highlight CF-MagNa’s efficacy as a potential adsorbent for water treatment, with promising applications in environmental remediation and sustainable water purification technologies.