Adsorption and Co-adsorption of 2,4-Difluoroaniline and Copper (II) Using Nickel-Manganese Ferrite Magnetic Biochar Derived from Orange Peel

The adsorption process is regarded as a promising technology for removing organics and heavy metals. In this study, we used orange peels as biomass feedstock and used nickel-manganese ferrite (Ni 1-x Mn x Fe 2 O 4 ) as the precursor solution to prepare magnetic mesoporous biochar (MBC). Using a Box-Behnken design response, we investigated the adsorption of 2,4-difluoroaniline (2,4-DFA), as well as the influence of four preparation parameters (activation temperature, the molar mass of Mn in Ni 1-x Mn x Fe 2 O 4 , activation time, and impregnation ratio). Based on the adsorption rate of 2,4-DFA, we obtained the following optimal preparation parameters of MBC: a temperature of 180 °C, a molar mass of Ni 0.75 Mn 0.25 Fe 2 O 4 , an activation time of 8 h, and an impregnation ratio of 3. Then, we investigated the adsorption capacity of MBC and the mutual effect of 2,4-DFA and copper (II) [Cu(II)] through single and binary systems. The adsorption processes of 2,4-DFA and Cu(II) could be satisfactorily fitted to a pseudo-second-order kinetic model. The adsorption amount of 2,4-DFA was comparable in both single and binary systems. However, the adsorption of Cu(II) in the binary system was inhibited, with the adsorption capacity decreasing by 19.55%. The adsorption isotherms of 2,4-DFA and Cu(II) to MBC fitted the Freundlich model. The maximum adsorption capacity of 2,4-DFA and Cu(II) could reach 66.30 mg/g and 10.44 mg/g at 313 K, respectively. MBC exhibited good regeneration performance through the combination of 90% ethanol and 1 M NaOH solution. The adsorption mechanism mainly included electrostatic interactions, hydrogen bonds, ion exchange, and π-π interactions.