Construction of Ag@ZIF-8/PVDF mixed-matrix ultrafiltration membranes with high separation performance for dye from high-salinity wastewater by microemulsion coupling with blending

In order to improve the separation performance and anti-fouling property of polyvinylidene fluoride (PVDF) ultrafiltration membranes, PVDF mixed matrix membranes (MMMs) were obtained by mixing PVDF with Ag@ZIF-8 using a simple one-pot microemulsion strategy. First, both Ag and ZIF-8 were generated in one micelle of the microemulsion during the formation of composites. After in-situ polymerization of microemulsion， the latex containing Ag@ZIF-8 was blended with PVDF by phase-inversion method to construct the MMMs. The small-sized Ag particles were closely distributed on the surface of ZIF-8 after the formation of ZIF-8 in micelles. The subtle interaction forces between the two facilitated the distribution of the composite in the PVDF matrix. In addition, the hydrophilic component in the latex improves the pore structure , the permeation and anti-fouling performance of the PVDF matrix compared to neat PVDF and the MMM with ZIF-8 added. Mixed-matrix ultrafiltration membranes with 0.3 wt% of microemulsion containing Ag@ZIF-8 exhibited good permeation ( J w  = 222 L m −2  h −1 ) and flux recovery rate ( FRR  = 82%). The well-distributed Ag@ZIF-8 in PVDF polymeric matrix strengthened the dye retention of MMMs from high-salinity wastewater, due to the interaction between Ag@ZIF-8 and dye molecules. This mixed-matrix ultrafiltration membrane also showed optimum dye rejection (97.3%) and low salt rejection (0.2%). The MMMs combined with Ag@ZIF-8 in this work are promising for the removal of dye contaminants for high-salinity wastewater, so as to achieve the goal of advanced treatment for high-salinity wastewater.