Breaking the trade-off between selectivity and permeability of nanocomposite membrane modified by UIO66@PDA through nonsolvent thermally induced phase separation method

Abstract

Developing polymer membranes with high permeability, fouling resistance, and rejection capability is a challenging task that requires the use of novel materials to enhance these properties. In this study, composite ultrafiltration membranes were fabricated by incorporating two types of metal–organic frameworks (MOFs), UIO66 and UIO66@PDA, into polyvinylidene fluoride (PVDF) using the nonsolvent thermally induced phase separation (NTIPS) method. The results demonstrated that the NTIPS method combined the characteristics of nonsolvent-induced phase separation (NIPS) and thermally induced phase separation (TIPS) to fabricate asymmetric membranes with a dense ultra-thin top layer and a bicontinuous network structure. Moreover, the introduction of 1.0 wt% UIO66@PDA into PVDF membranes yielded notable improvements in mechanical strength, thermal stability, and porosity. Concurrently, this led to a water flux rise from 182.5 to 464.7 L·m−2·h−1, and enhanced BSA and HA rejection to 96% and 83%, respectively. Additionally, there was a significant improvement in the membrane's antifouling capacity, achieving a water flux recovery ratio of 93%. This was facilitated by the increased hydrophilicity of UIO66@PDA, which attracted more water molecules and reduced membrane fouling. This work offers a solution to overcome the permeability-selectivity trade-off in membrane separation by hydrophilic modification of hydrophobic membranes, while also addressing fouling issues.