Synthesis of magnetic rice husk biochar and its application in the adsorption of Ni(II) from aqueous solutions

Ferrate, as an internal oxidation modifier, is rarely used in the preparation of magnetic biochar. This research promotes rice shell charcoal modified by K2FeO4 preparation of oxygen-containing groups and gamma-Fe2O3 magnetic biochar. Magnetic rice husk biochar (MBC) is prepared to adsorb Ni(II) from aqueous solutions. The effects of various parameters on the adsorption of Ni(II) by MBC have been studied, and the results show that MBC has an excellent adsorption capacity for Ni(II). At 25 degrees C and pH 7.0, the removal rate of Ni(II) reaches 96.1% within 24 h at an adsorbent dose of 0.5 g/L when the initial Ni(II) concentration is 20 mg/L. The kinetic model conforms to the pseudo-second-order kinetic model and the intra-particle diffusion model within 36 h. Moreover, the adsorption data were successfully reproduced by the Langmuir isotherm, and the maximum adsorption capacity is 42.69 mg/g. The adsorption data conform to the D-R model, and the calculated average adsorption free energy is 41.03 kJ/mol, indicating that the adsorption process is mainly chemical adsorption. Thermodynamic study indicates that the endothermic adsorption process is spontaneous and can be promoted by the increase in temperature. This study was expected to provide a reference and theoretical basis for the treatment of Ni(II)-containing wastewater using modified rice husk biochar.