Preparation of C-based Magnetic Materials from Fruit Peel and Hydrochar using Snake Fruit (Salacca zalacca) Peel as Adsorbents for the Removal of Malachite Green Dye

In this study, fruit peel-based magnetic (M-Sp) and hydrochar-based magnetic (M-HSp) materials were successfully synthesized by hydrothermal and magnetization treatments. Characterization using X-ray diffraction, Fourier-transform infrared spectroscopy, vibrating sample magnetometry, and scanning electron microscopy-energy dispersive spectroscopy confirmed their successful synthesis. The materials were applied as adsorbents for the removal of malachite green (MG) dye. Equilibrium adsorption occurred at 90 min according to the PSO kinetic model, and the adsorption followed the Langmuir isotherm. The adsorption capacity of the materials was improved by the hydrothermal and magnetic treatments compared to that of the untreated initial material. The adsorption capacities of M-Sp and M-HSp were 69.444 and 88.889 mg/g, respectively. The M-Sp and M-HSp adsorbents could be reused for up to four regeneration cycles compared to the three cycles for the initial material. The adsorption mechanism of MG dye by the M-Sp and M-HSp adsorbents was suggested to occur via hydrogen bond, electrostatic, π-π, and physical interactions. The magnetic materials prepared in this study had a high adsorption capacity and adsorbent reusability, rendering them promising for use in dye removal and to facilitate separation between adsorbents and adsorbates.