Efficient charge transfer in aluminum-cobalt layered double hydroxide derived from Co-ZIF for enhanced catalytic degradation of tetracycline through peroxymonosulfate activation

In consideration of the complex synthesis of layered double hydroxides (LDHs), a simple and efficient strategy was needed to design and fabricate LDHs with high performance. In this study, aluminum-cobalt layered double hydroxide (AlCo-LDH) with uniformly distributed component was synthesized by in-situ etching of cobalt zeolitic imidazolate framework (Co-ZIF) at room temperature. The obtained AlCo-LDH showed high catalysis performance of tetracycline (TC) degradation via the activation of peroxymonosulfate (PMS). The removal efficiency can reach to 92.3% within 5 min and 49.1% of TOC removal efficiency could be obtained in 30 min. Moreover, the degradation rate constants of AlCo-LDH/PMS system (0.980 min(-1)) was about 16.6 times higher than Co-ZIF/PMS system (0.059 min(-1)). The unique hydrotalcite-like layered structure of AlCo-LDH with large surface area and volume made TC molecules diffused and interacted with the reaction sites more easily. More importantly, the higher content of Al ions in AlCo-LDH catalyst helped the low content of Co ions to activate PMS. The forming process of AlCo-LDH and the TC degradation mechanisms were investigated. The quenching experiments combined with electron paramagnetic resonance (EPR) analysis showed the SO4 center dot- and O-1(2) radicals were the main reactive species for TC degradation. Moreover, the AlCo-LDH catalyst was stable in water for the negligible leaking of metal ions. Significantly, the AlCo-LDH/PMS system was effective and almost unaffected by pH values, organic and inorganic matters in water. In addition, high removal efficiencies were achieved in various real samples by the AlCo-LDH/PMS system. This work provided a novel and facile route to synthesis advanced MOF-derived LDHs catalyst with high performance in remediation of actual wastewater.