Zeolitic imidazolate metal organic framework ZIF-8 with ultra-high adsorption capacity bound tetracycline in aqueous solution

ZIF-8 nanoparticles were prepared with a convenient method at room temperature. The morphology and components of the ZIF-8 were characterized by scanning electron microscopy (SEM), powder X-ray diffraction spectroscopy (PXRD), thermogravimetric analysis (TGA), Fourier-transform infrared spectroscopy (FT-IR) and zeta potential analysis. The ZIF-8 nanoparticles were relatively stable under neutral and alkaline solutions, while their structure easily collapsed partially in the strong acidic aqueous solution. The adsorption kinetics and isotherms of ZIF-8 for tetracycline were evaluated in detail. The effects of key parameters such as pH, contact time, temperature and ionic strength on the adsorption of tetracycline were studied. The data on the adsorption of tetracycline on the ZIF-8 nanoparticles fitted well to the pseudo-second-order kinetics model, while the adsorption isotherm data can be explained respectively by the Langmuir isothermal model and the Freundlich isotherm model to varying degrees. The equilibrium quantity of tetracycline on ZIF-8 obtained in adsorption kinetic studies was 124.6 mg g(-1) at 25 degrees C, while the value calculated by the Langmuir isotherm model was above 1000 mg g(-1) at the same temperature. This implied that the adsorption capacity of ZIF-8 to tetracycline can be improved to a large extent. The analysis of the adsorption mechanism showed that electrostatic attraction and p-p stacking interaction both played crucial roles in the adsorption process. Regeneration experiments indicated that the used adsorbent still showed excellent applicability after four rounds of recycling.