Optimize the preparation of FeO-modified magnetic mesoporous biochar and its removal of methyl orange in wastewater.

In this paper, Eichhornia Crassipes stems were used as biomass feedstock, and Fe was used as the precursor solution to prepare FeO-modified magnetic mesoporous biochar (FeO@BC). By using Box-Behnken design (BBD) response surface methodology, the influences of three preparation parameters (X = Fe concentration, X = pyrolysis temperature and X = pyrolysis time) on the adsorption of methyl orange (MO) by FeO@BC were investigated, and a reliable response surface model was constructed. The results show that XX and XX have a significant influence on the adsorption of MO by FeO@BC. The surface area and pore volume of FeO@BC are controlled by all preparation parameters. The increase of pyrolysis time will significantly reduce the -OH on the surface of FeO@BC and weaken its MO adsorption capacity. Through the numerical optimization of the constructed model, the optimal preparation parameters of FeO@BC can be obtained as follows: Fe concentration = 0.27 mol/L, pyrolysis temperature = 405 °C, and pyrolysis time = 3.2 h. The adsorption experiment shows that the adsorption of FeO@BC to MO is a spontaneous exothermic process, and the adsorption capacity is maximum when pH = 4. The adsorption kinetics and adsorption isotherms of FeO@BC to MO conform to the pseudo-second-order kinetics and Sips model, respectively. Mechanism analysis shows that electrostatic interaction and H bond formation are the main forces for FeO@BC to adsorb MO. This research not only realizes a new way of resource utilization of Eichhornia Crassipes biomass but also enriches the preparation research of magnetic biochar.