Fabricating iron-cobalt layered double hydroxide derived from metal-organic framework for the activation of peroxymonosulfate towards tetracycline degradation

Highlights: • FeCo-LDH was prepared by sacrificing ZIF-67 templates in Fe³⁺ ethanolic solution. • FeCo-LDH can efficiently degrade tetracycline (TC) by activating PMS. • SO₄.• - and O₂• - radicals were the main reactive species in FeCo-LDH/PMS system. • FeCo-LDH catalyst exhibited high removal efficiency after three recycle test. • The FeCo-LDH/PMS system keep high efficiency in actual water. Herein, iron-cobalt layered double hydroxide (FeCo-LDH) was synthesized by sacrificing Co-containing zeolite imidazolate framework materials (ZIF-67) in iron ethanolic solution at room temperature. The catalytic performances of catalysts were investigated by activating peroxymonosulfate (PMS) for tetracycline (TC) degradation. Experimental results were demonstrated that FeCo-LDH with molar ratios of Fe and Co was 1.5 (FeCo-LDH-1.5) exhibited the highest catalytic activity, in which the TC degradation efficiency was reached to 92% within 5min. The system of FeCo-LDH-1.5/PMS exhibited high stability and high efficiency in the influencing factor experiments including TC concentrations, initial pH, coexisting anions (Na⁺, Cl^-, SO₄²⁻) and humic acid (HA). Results of quenching experiments and electron paramagnetic resonance (EPR) characterization showed that O₂^{• -} and SO₄^{• -} radicals were the foremost reactive species for TC degradation. Liquid chromatograph - mass spectrometer (LC-MS) and three-dimensional excitation emission matrix fluorescence spectro photometer (3D EEMs) were conducted to investigate the degradation intermediate and possible degradation pathway. Moreover, high degradation efficiency was implemented in actual wastewater by the FeCo-LDH-1.5/PMS system. Compared to Fe³⁺/PMS and Co²⁺/PMS homogeneous system, the FeCo-LDH-1.5/PMS system was exhibited advantages in catalytic activity and high reusability. This study provided a convenient method to synthesis advanced hydrotalcite-like catalysts, which showed remarkable performance in actual wastewater treatment.