Enhanced peroxymonosulfate activation for tetracycline removal using magnesium–aluminum layered double hydroxide/zeolitic imidazolate framework-8 nanocomposite

Advanced oxidation process (AOP) utilizing peroxymonosulfate (PMS) has emerged as effective methods for environmental remediation due to their high reactivity and selectivity. However, designing hierarchical catalysts with multiple active sites for PMS activation remains an important challenge. Here, a nanocomposite was synthesized based on zeolitic imidazolate framework-8 (ZIF-8) formed on magnesium-aluminum layered double hydroxides (Mg-Al LDH) to facilitate tetracycline (TC) removal through PMS activation. The effects of key operational parameters, including PMS dose, nanocomposite concentration, initial pH, pollutant concentration, and reaction duration, were investigated. The results showed that approximately 97.5% of TC was removed within 12 min at pH = 7, for TC concentration of 25 mg/L, Mg-Al LDH/ZIF-8 dose of 9 mg/L, PMS dose of 0.28 mM. The LDH/ZIF-8/PMS system exhibited superior efficiency for TC removal compared to Mg-Al LDH/ZIF-8, Mg-Al LDH, and ZIF-8. The process was analyzed using Langmuir, Freundlich, and Temkin isotherm models, with the Langmuir model exhibiting the highest correlation coefficient (R2= 0.9923), confirming a monolayer catalytic mechanism on a homogeneous surface. Results from quenching experiments indicated that sulfate and hydroxyl radicals (SO₄•⁻ and •OH) are primary species driving the degradation of TC. These findings provide valuable insights on potential application of Mg-Al LDH/ZIF-8 for environmental purification.