Research on effects of loading methods on magnetic biochar properties

Nano-Fe_3O_4 -loaded biochar (magnetic biochar) has the characteristics of rich surface functional groups, medium and large pores, superparamagnetism, high electrical conductivity and alkalinity. It is widely used in composting, sewage treatment, anaerobic digestion, soil remediation, and other fields. To explore the effect of loading methods on the properties of biochar loaded by nano-Fe_3O_4 biochar loaded by nano-Fe_3O_4 was prepared by chemical coprecipitation method (MBC1), sol-gel method (MBC2) and ball milling method (MBC3). The results showed that nano-Fe_3O_4 was flocculent on the surface of MBC1, while it was clear and spherical on MBC2 and MBC3. Meanwhile, new functional groups (Fe—O—C and Fe—O) appeared in biochar loaded by nano-Fe_3O_4 imparting magnetic properties. The magnetic saturation intensity of MBC1, MBC2 and MBC3 was 8.619×10^-2, 8.607×10^-2, 8.960×10^-2 A·m^2·g^-1, respectively. Compared with biochar, the average pore size of nano-Fe_3O_4 loaded on biochar increased by 240%-330%, electrical conductivity increased by 17%-26%, and pH raised to 8-9. Among nano-Fe_3O_4 loaded on biochar prepared by three methods, the crystallinity of MBC1-Fe_3O_4 was the lowest, and the dispersion of MBC3-Fe_3O_4 was the highest. This study provides a reference for the preparation of biochar loaded by nano-FeO and the influence of loading methods.