Photo-Fenton degradation of tetracycline hydrochloride with Fe2O3-on-ZrO2 polypods derived from MIL-88B-on-UiO-66-NH2 within full pH range: Kinetics, degradation pathway and mechanism insight

Photo-Fenton reaction has received increasing attention in removing antibiotics in water. Herein, Fe2O3-on-ZrO2 polypods were designed and synthesized via metal organic frameworks (MOFs) derivation strategy combined with reflux heating and baking. The experimental results showed that under Ultraviolet-visible (UV-vis) light irradiation, more than 95 % tetracycline hydrochloride (TC-HCl) was degraded by Fe2O3-on-ZrO2 with Fe/Zr mole ratio of 1.3 in 25 min within full pH range. Mainly due to the following points, there were abundant Fe2O3-on-ZrO2 heterojunctions, which conduced to transfer photo-induced electrons (e(-)) from ZrO2 to Fe2O3, thus accelerating the iron cycle. Besides, OH- adsorbed was oxidized to hydroxyl radicals (center dot OH) by holes (h(+)) in the valence band (VB) of ZrO2, and ZrO2 also enhanced the stability of the catalyst and reduced the leaching of iron ions. Finally, the reasonable degradation pathway and degradation mechanism were speculated by high performance liquid chromatography-mass spectrometry (HPLC-MS), electron spin resonance technology (ESR), scanning Kelvin probe (SKP), the conduction band (CB) and VB positions of Fe2O3-on-ZrO2, etc. This work exhibited a new structure and degradation mechanism, which would further encourage researchers to study the rational regulation of materials with special morphology and structure.