Magnetic Composite Carbon from Microcrystalline Cellulose to Tackle Paracetamol Contamination: Kinetics, Mass Transfer, Equilibrium, and Thermodynamic Studies

This study reported a one-spot preparation of magnetic composite carbon (MCC@Fe) from microcrystalline cellulose (MC). The pure cellulose was impregnated in iron (III) chloride solution and carbonized at 650 °C. The MCC@Fe composite adsorbent underwent various characterization techniques. XRD identified nanostructured Fe₃O₄ particles with an average crystallite size of 34.3 nm embedded in the core subunits of the material. FESEM images indicated a rough and irregular surface, with some cavities along its surface, incorporating Fe₃O₄ nanoparticles, while EDS analysis confirmed the presence of elements like Fe, C, and O. Notably, combining thermal and chemical treatments produces a composite with more pores and a high specific surface area (500.0 m² g^-1) compared to MC (1.5 m²/g). VSM analysis confirmed the magnetic properties (0.76 emu/g), while the Hydrophobic Index (<i>HI</i>) showed that MCC@Fe was hydrophobic (<i>HI</i> 1.395). The adsorption studies consisted of kinetic, mass transfer, equilibrium, and thermodynamics studies. Kinetic study of the adsorption of paracetamol on MCC@Fe composite proved to be rapid, and the time necessary for covering 95% of the surface (t_0.95) was lower than 27 min following the fractal-like pseudo-first-order model (FPFO). Liu's isotherm proved to be the most appropriate for understanding the adsorption equilibrium. Remarkably, the maximum sorption capacity (Q_max) of paracetamol was 34.78 mg g^-1 at 45 °C. The Δ<i>H</i>° value (+27.00 kJ/mol) and the negative Δ<i>G</i>° values were consistent with the physisorption mechanism and favorable process. Furthermore, the mass transfer mechanism showed that the transfer is governed by the intraparticle diffusion model, with surface diffusion being the rate-limiting step when considering the <i>Biot</i> number greater than 100. This research displayed a single-route production of inexpensive magnetic nano adsorbents capable of efficiently eliminating paracetamol from aqueous environments.