Carbon coated Fe0.65Ni0.30Mn0.05 magnetically separable adsorbent for phenanthrene removal

Fe_0.65Ni_0.30Mn_0.05 invar alloy was produced via the polyol process, employing a polyvinyl alcohol (PVA) solution in varying weight ratios (50% and 66% PVA), and carbonized at different temperatures in argon (Ar) atmosphere to create a magnetic core-shell structure of Fe_0.65Ni_0.30Mn_0.05@C. The structural, morphological, and magnetic characteristics of the prepared material were analyzed using X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), Brunauer-Emmett-Teller (BET) method, Fourier-transform infrared spectroscopy (FTIR), and vibrating sample magnetometry (VSM). The carbonization process applied to these samples enhances their suitability for the adsorption of weakly polar or nonpolar organic molecules. The performance analysis of the synthesized magnetic adsorbent indicates that the sample prepared using 66% PVA, annealed at 550 °C , achieved the highest removal efficiency of 99.5% for phenanthrene as a model compound for polyaromatic hydrocarbons (PAHs) in aqueous media. The adsorption process described by the Temkin model is adept at exploring the relationship between indirect interactions among adsorbates and the adsorbent. This includes the initial interaction of adsorbate molecules with the most energetic sites, followed by subsequent interactions influenced by the presence of already adsorbed molecules. This is also confirmed by the compliance with the second-order kinetics. The optimum sample exhibits a superparamagnetic property with high saturation magnetism (22 emu/g), facilitating its recovery from treated water effluent via magnetic separation. Conclusively, the synthesized magnetic adsorbent materials show great potential as effective solutions for the remediation of water contaminated with PAHs.