Effect of solution chemistry on the stability and transport of ZIF-8 in saturated porous media

Metal-organic frameworks (MOFs) nanoparticles have been regarded as one of the most important materials for high-performance applications in various fields, including environmental protection. Understanding the migration behavior of MOFs in the environmental media is critical for evaluating their opportunities and risks. In this study, the effect of pH, ionic strength, and NOM (fulvic acid and citric acid) were selected to investigate the transport and retention of ZIF-8 in saturated porous media . Experimental results showed that the released Zn 2+ of ZIF-8 was significantly increased by the high concentration of ionic strength and citric acid . There were new ZIFs phases detected in the transport process. ZIF-8 had weak mobility with a recovery of transport mass ≈ 2.3% in 1 mg/L citric acid at pH 6, while the maximum effluent recovery was 33.7% in the 100 mM NaCl at pH 8. Under all examined conditions, ZIF-8 was mainly retained at segments near the column inlet. Straining increased the retention of ZIF-8 in porous media. These results indicated that physicochemical factors and particle-specific properties played important roles in influencing ZIF-8 transportability, which would lead to the more complex evaluation of the environmental behaviors of MOFs.