Polyethersulfone-MIL-53(Al) Nanoparticles Mixed Matrix Membranes for Separation of Aqueous Dye Solutions

Nanofiltration (NF) is a very important technique in separation and purification of aqueous and non-aqueous mixtures in several applications, such as the retention of dyes from water, which is the largest application in this field. Nonetheless, it is still a key issue to enhance the rejection performance and improve the flux, the key factors for the performance of the final membrane. Accordingly, MIL-53(Al) nanoparticles were utilized in this research work because of their small pore sizes, significant hydrophilicity and outstanding water stability.

In this study, the synthesis of the MIL-53(Al) nanoparticles was conducted. Then, the preparation of polyethersulfone (PES)-MIL-53(Al) mixed matrix membranes was done through the VIPS-NIPS method, which is the vapor-induced phase inversion (VIPS) method coupled with non-solvent-induced phase inversion (NIPS) technique, in which the co-solvent of 1,4-dioxane was employed. Finally, the prepared nanoparticles and membranes were characterized using several techniques including attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), X-ray diffractometry (XRD), field-emission scanning electron microscopy (FE-SEM), inductively coupled plasma optical emission spectroscopy (ICP-OES), and contact angle analyses.

Different membrane compositions with various MIL-53(Al) contents were prepared so that a membrane with superior performance in dye rejection application and high flux can be achieved. The performance of the fabricated membranes was investigated for rejection of various dyes in aqueous solutions including Reactive Red (RR), Direct Yellow (DY), Methyl Green (MG), and Crystal Violet (CV), based on which a great separation performance (dye rejections of 99.8, 99.5, 99.2, 98.8 and 97.1 for RR, MG, DY, CV and MB, respectively) and an excellent water flux (4.8 L/m2.h.bar) were provided by the membrane containing 0.06 wt% MIL-53(Al)..