Robust ZIF-8 and its derivative composite membrane for antibiotic desalination with high performance

Zeolitic imidazolate framework (ZIF) membranes have great potential applications in nanofiltration. However, preparing continuous and intact ZIF membranes on the surface of a substrate remains challenging. In this study, we assembled ZIF-8 nanoparticles in situ in the pores of a porous alumina substrate via a freezing-assisted counter-diffusion method. Although a continuous ZIF-8 membrane was not formed on the surface of the substrate, the obtained nano-confined composite membrane was dense enough to separate antibiotics and salt. The rejection rate of tetracycline was above 99 %, while that of sodium chloride was below 20 %, demonstrating good antibiotic desalination performance. The permeance of the ZIF-8 membrane reached 23.5 LMH/bar. Due to the nano-confined structure, the obtained ZIF-8 composite membrane was robust. Besides, polishing the surface layer did not reduce the separation performance. Moreover, sulfurizing the ZIF-8 membrane improved its stability in water. It also improved the permeance to 31.3 LMH/bar, which remained stable for 100 h. Therefore, the obtained robust ZIF-8 membrane and its derivative composite membrane fabricated via freezing-assisted counter-diffusion have great potential in antibiotic desalination.