GAC@Fe3O4, LDHs@Fe3O4 and GO@Fe3O4 applied for tetracycline hydrochloride removal in three-dimensional heterogeneous electro-Fenton process

Tetracycline hydrochloride (TC-HCl) was harmful to human as well as ecology due to its persistence. Layered double hydroxides (LDHs), granular activated carbon (GAC) and graphene oxide (GO) were selected as the catalyst supporting materials for the three-dimensional heterogeneous electro-Fenton (3D-EF) process. The three materials were then used to prepare catalyst particles of GAC@Fe 3 O 4 , LDHs@Fe 3 O 4 and GO@Fe 3 O 4 to degrade TC-HCl. The characterizations of the LDHs@Fe 3 O 4 (8:2) particles were done by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy and Brunauer– Emmett–Teller. At pH of 3, the proper ratio of supporting materials (LDHs, GO, GAC) to Fe 3 O 4 improved the removal efficiency of TC-HCl. GAC@Fe 3 O 4 (8:2), LDHs@Fe 3 O 4 (8:2) and GO@Fe 3 O 4 (2:8) obtained better performance, LDHs and GO used as supporting material had better performance than GAC. Further study on the effect of different pH values showed that the LDHs@Fe 3 O 4 (8:2) acquired the highest chemical oxygen demand (COD) removal efficiency (63.03%) at pH of 7. LDHs@Fe 3 O 4 (8:2) and GO@Fe 3 O 4 (2, 8) obtained similar COD removal efficiencies at pH of 3. The percentage of Fe 2+ leaching to solution was 2% for the LDHs@Fe 3 O 4 , which was 2.9% for the GAC@Fe 3 O 4 and 5.46% for the GO@Fe 3 O 4 . Experimental results showed that more H 2 O 2 and • OH were produced on the surface of the LDHs with pH of 7. Finally, GC-MS was used to determine the degradation pathway of TC-HCl. The LDHs had obvious advantages as catalyst supporting materials for the 3D-EF process.