A Simple One‐Pot Pyrolyzed Synthesis of Ternary Magnetic ZnFe₂O₄/α‐Fe₂O₃/Biochar Nanocomposites for Adsorptive Removal of Direct Red 79 in Aqueous Solution

Abstract

Ternary magnetic ZnFe₂O₄/α‐Fe₂O₃/biochar nanocomposites (MBCs) were successfully synthesized by one‐pot pyrolysis in oxygen‐limited environment using ZnCl₂, FeCl₂ as an activating agent, and precursors. The following conditions were found to be optimal for MBCs: activation temperature of 700 °C, mass ratio of ZnCl₂ and FeCl₂ of 1, and activation time of 2 h. The prepared MBCs were evaluated for textural characteristics such as crystalline structure, surface chemical functional groups, vabriation mode, magnetic properties, pore structure, morphology and the adsorption capacity using the methods such as X‐ray diffraction, Fourier transform infrared spectroscopy, Raman spectra, vibrating sample magnetometer, N₂ adsorption‐desorption isotherms, scanning electron microscopy and transmission electron microscopy. The prepared MBCs had porous structures, the highest S_BET (782.37 m² g⁻¹), and pore volume (0.54 cm³ g⁻¹) when the mass ratios of ZnCl₂ and FeCl₂ were 1, and the activation temperature was 700 °C, and the magnetic parameters were found at a H_c of 60 Oe, M_s of 13.03 emu g⁻¹ and M_r of 1.07 emu g⁻¹. Adsorption equilibrium studies indicate that the DR79 adsorption followed the Langmuir model and Sips model. The DR79 adsorption capacity of the MBC‐700‐1 has the largest value (676.8 mg g⁻¹). The adsorption process was influenced by multiple diffusion steps, with the pore diffusion process serving as the rate‐controlling step. These findings show that MBCs adsorb DR79 efficiently and can be easily separated and recovered using an external magnetic field. The prepared MBCs have the potential to be high‐performance organic pollutant wastewater adsorbents.