Enhancing the pervaporation performance of PEBA/PVDF membrane by incorporating MAF-6 for the separation of phenol from its aqueous solution

Phenol is highly toxic and carcinogenic even at low concentrations. This study focused on preparing high-performance mixed matrix membranes (MMMs) for the pervaporation separation of phenol from its aqueous solution. A highly-efficient zeolitic metal azolate framework, RHO-[Zn(Heim)₂] (MAF-6, Heim = 2-ethylimidazole) was incorporated into the polyether block amide (PEBA-2533) supported on the polyvinylidene fluoride (PVDF) ultrafiltration membrane. The MAF-6 was chosen as the filler due to its inherent hydrophobic surfaces and aperture size (7.6 Å), which is larger than the molecular kinetic diameter of phenol (6.6 Å). Effects of the casting solution concentration, active layer thickness, MAF-6 loading, operating temperature, and phenol concentration were systematically investigated. With the increase of the MAF-6 loading ratio X from 0 to 7, the phenol flux of the membrane was gradually enhanced, but the water flux was reduced. For 1000 ppm phenol aqueous solution at 80 °C, MAF-6–7@MMM displayed the optimal separation factor of 25.9 with a phenol flux of 89.2 g∙m⁻²∙h⁻¹. The pervaporation separation index (PSI) of the MAF-6–7@MMM was 1317.7 kg∙µm∙m⁻²∙h⁻¹ at 80 °C, which was much higher than the PEBA/PVDF membrane (787 kg∙µm∙m⁻²∙h⁻¹). Impressively, an increasing feed temperature enhanced the phenol flux more prominently than water, owing to the hydrophobicity and porosity of MAF-6. Consequently, the resultant MAF-6-X@MMMs broke the trade-off limitation between phenol permeability and selectivity. The as-prepared membrane also exhibited exceptional long-term stability, suggesting its prospect of industrial application.