Size-controlled synthesis of ZIF-8 nanoparticles by high gravity technology for enhanced tetracycline adsorption

Abstract

ZIF-8 as a typical metal–organic framework (MOF) is regarded as a promising adsorbent owing to its ultra-high specific surface area and well-defined porous architecture. Smaller-sized MOFs with more exposed active sites are conducive to the rapid and efficient adsorption of molecules. However, achieving precise nanoscale control of MOF particle sizes remains a challenge. Herein, we report a facile method to prepare uniform ZIF-8 nanoparticles with controllable sizes of 20–120 nm by high gravity technology in the rotating packed bed (RPB) reactor. Compared with the conventional stirred tank reactor (STR), the products prepared by RPB showed narrower size distribution and smaller particle size, with an average reduction of 30 %. The as-synthesized ZIF-8 nanoparticles demonstrated a pronounced size-dependent adsorption behavior for tetracycline in aqueous solutions. Particularly, 20 nm ZIF-8 nanoparticles exhibited the highest adsorption capacity of about 217 mg g⁻¹, surpassing both micro-sized ZIF-8 (189 mg g⁻¹) and previously reported ZIF-8 and its composites. Moreover, the effects of adsorbent dosage, pH, temperature and coexisting ions on the adsorption performance were also investigated. A rational adsorption mechanism of TC adsorption over ZIF-8 nanoparticles was proposed. These findings are of great significance for selecting nano-absorbents with the appropriate size to achieve optimal adsorption in real-world use.