Boosting pervaporation performance of polyether block amide membranes by embedding structural-evolution zeolitic imidazolate framework-71s for phenol/water separation

Given the increasing concerns for both the environment and human health, the treatment of wastewater containing phenolics has emerged as a pressing yet daunting matter. In this work, the mixed matrix membranes (MMMs) with exceptional performance have been created by introducing controllable morphology and structure zeolitic imidazolate framework-71s (ZIF-71s) into polyether block amide (PEBA) matrix for the purpose of phenol-water separation. The impacts of ZIF-71s dimension and ZIF-71s loading amount on the separation performance were comprehensively analyzed, as well as operational temperature and operational concentration on the separation performance. The crystal transformation of three-dimensional ZIF-71K nanoparticles into two-dimensional ZIF-71P nanosheets was accomplished by altering the modulators in aqueous system. The presence of ZIF-71s could lead to a decrease in water flux, while the phenol permeation flux was essentially unaffected. The filling of two-dimensional ZIF-71P nanosheets established a classic “brick-and-mortar” structure within the polymeric bulk, which resulted in the enhancement of tortuous pathways and energy barriers for water penetration, hence further boosted the membrane selectivity. For an operating temperature of 50 °C and a phenol concentration of 1000 ppm, the ZIF-71P/PEBA-21 MMMs exhibited separation performance with total permeate flux and separation factor of 911.10 g·m−2·h−1 and 18.96, while the ZIF-71K/PEBA-21 membrane demonstrated total permeate flux and separation factor of 965.49 g·m−2·h−1 and 17.74. And the MMMs presented a superior separation performance in comparison with the PEBA/PVDF membrane. On top of that, the resultant MMMs also demonstrated promising long-term stability as phenol enrichment methods, which holds significant promise for implementation in the recovery of phenol from relevant industrial wastewater.