Highly dispersed natural Goethite/Fe3O4 heterogeneous Fenton-like catalyst for efficient tetracycline degradation: Rapid accumulation of hydroxyl radicals by Fe–O–Si bonds

A highly dispersed catalyst (Fe3O4/NFe) was prepared with Fe3O4 and natural goethite (NFe) to remove TC in the heterogeneous Fenton-like system. A large amount of ≡Si–O–Si on NFe could be destroyed by the grinding method to produce ≡SiO• on the surface. Fe3O4 nanoparticles were successfully grown on the NFe with the formation of Fe–O–Si bonds, the Fe3O4/NFe retained the magnetic performance and the larger dispersion from predecessors. In the Fe3O4/NFe/H2O2 process, the degradation performance of tetracycline (TC) could reach 90.1% in 30 min. Moreover, the toxicity of TC and its intermediates was estimated in ECOSAR software. The ESR analysis and quenching experiments revealed the contribution of •OH, HO2•, and ≡SiO• in TC removal. A part of •OH, HO2• in solution could decompose TC, and the ≡SiO• on surface also directly remove TC. The strong interactions of Fe–O–Si bonds improved the generation of abundant •OH, and the total concentration of •OH by Fe3O4/NFe in 30 min is 244.7 μmol/L. In DFT analysis, the electrons redistribution between Fe3O4 and NFe could easily provide the electrons to activate H2O2, and improved the adsorption of H2O2 in Fe3O4/NFe/H2O2 system. The removal rate of TC still reached 73.3% by Fe3O4/NFe after five cycles. In the present work, this Fe3O4/NFe has been shown to be a promising alternative to traditional homogeneous Fenton method.