Heterogeneous Fenton system driven by magnetic graphene-like biochar for degrading tetracycline

In this study, a novel catalyst with high efficiency and low cost was synthesized from farmland waste peanut shells by one-step pyrolysis modification method via K2FeO4, and employed for the catalytic degradation of tetracycline (TC). The magnetic potassium ferrate modified graphene-like biochar catalyst (PFGB) exhibited a high porosity, a highly graphitized structure, and a large specific surface area (857.09 m(2) g(-1)) which was almost 30 times higher compared with peanut shell biochar, and were found to contain more functional groups. The formation and distribution of Fe3O4 and Fe-0 nanoparticles on the surface/pores of PFGB provided more active sites for promoting adsorption and catalytic degradation reactions, and accelerated Fe(II)/Fe(III) recycle. Under the optimal conditions (pH = 3.5, catalyst dosage = 0.5 g L-1, H2O2 concentration = 10 mmol L-1), about 98 % of TC were degraded within 90 min when the initial concentration of TC was 150 mg L-1, and PFGB could perform effectively over a wide pH range of 3-6. Furthermore, PFGB exhibited the advantages of convenient magnetic separation and strong reusability, maintaining a TC removal rate of similar to 90 % after five cycles of experiments. The results of free radical quenching experiment and electron spin resonance analysis revealed that center dot OH and O-1(2) were the main active species in the radical and non-radical pathways, respectively. This study indicated that PFGB, a catalyst developed for heterogeneous Fenton-like systems, possessed high efficiency, stability and reusability, and could be promising for the removal of TC in wastewater and other polluted waters.