Optimize the preparation of Fe_3O_4-modified magnetic mesoporous biochar and its removal of methyl orange in wastewater

摘要

In this paper, Eichhornia Crassipes stems were used as biomass feedstock, and Fe2+ was used as the precursor solution to prepare Fe3O4-modified magnetic mesoporous biochar (Fe3O4@BC). By using Box-Behnken design (BBD) response surface methodology, the influences of three preparation parameters (X-1=Fe2+ concentration, X-2=pyrolysis temperature and X-3=pyrolysis time) on the adsorption of methyl orange (MO) by Fe3O4@BC were investigated, and a reliable response surface model was constructed. The results show that X1X2 and X1X3 have a significant influence on the adsorption of MO by Fe3O4@BC. The surface area and pore volume of Fe3O4@BC are controlled by all preparation parameters. The increase of pyrolysis time will significantly reduce the -OH on the surface of Fe3O4@BC and weaken its MO adsorption capacity. Through the numerical optimization of the constructed model, the optimal preparation parameters of Fe3O4@BC can be obtained as follows: Fe2+ concentration = 0.27 mol/L, pyrolysis temperature = 405 degrees C, and pyrolysis time = 3.2 h. The adsorption experiment shows that the adsorption of Fe3O4@BC to MO is a spontaneous exothermic process, and the adsorption capacity is maximum when pH = 4. The adsorption kinetics and adsorption isotherms of Fe3O4@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 Fe3O4@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.