Facile fabrication of three-dimensional hierarchical porous ZIF-L/gelatin aerogel: Highly efficient adsorbent with excellent recyclability towards antibiotics

The environmental concerns and health risks caused by antibiotics have gained growing attention. Metal-organic frameworks (MOFs) are promising adsorbents for antibiotics removal, while limited by poor recyclability due to their powder form. In this study, via frothing and low-temperature carbonization, three-dimensional hierarchical porous ZIF-L/foaming gelatin aerogels (ZIF-L/FGA200) were prepared and targeted to tetracycline (TC) removal. As evidenced by multiple characterizations, ZIF-L was successfully integrated with gelatin aerogels, and the homodisperse of ZIF-L on FGA200 avoiding the agglomeration with more exposed active sites enhanced the adsorption performance as the maximum adsorbing capacity was up to 387.6 mg g-1. The adsorption behavior was well described with pseudo-second-order kinetics and Freundlich isotherm models. The effects of pH, coexisting ions and humic acid were investigated. Based on experimental data and characterizations, several possible adsorbing principles were proposed including electrostatic interaction, hydrogen bonding, pi-pi interaction and pore filling. Besides, treatment with multiple antibiotics and real samples were carried out. High removal efficiency (>95%) at different flow velocities (1.80-9.65 mL min-1) and satisfactory treatment volume in fixed-bed column adsorption demonstrated the good potentiality of ZIF-L/FGA200 towards practical applications. Moreover, excellent recyclability of ZIF-L/FGA200 was proved after nine adsorption-desorption cycles as the diminished performance was around 8% from 95% to 87%. Overall, ZIF-L/FGA200 was expected to be a potential adsorbent aiming at antibiotic elimination and this strategy might be suitable for loading various materials to prepared advanced composite materials.