Manifestation of UiO-66-Zr MOF-enabled photocatalytic membranes for successive separation and degradation of dye mixtures in water remediation

Abstract

The use of metal-organic framework (MOF) nanoparticles both as a separation-enhancer and as a photocatalyst has been demonstrated by suitably embedding them into polysulfone (PSU) membranes. These MOF-nanoparticles with Zr-metal and 2-aminoterephthalic-ligand, namely UiO-66-NH2, are synthesized via solvothermal and embedded into the PSU-membranes via solvent-casting process, confirmed via XRD and IR analysis. The skin-deep presence of MOFs and enhancements in the depth of pore-channels within membrane are confirmed through FESEM images. A favorable surface-charge and hydrophilic nature of the MOF-membrane are confirmed via zeta-surface potential and water contact angle analysis, respectively. Consequently, the water-flux efficacy of the optimized MOF-embedded membrane is estimated to be ∼59 L/m2h, while it is ∼20 L/m2h for pristine-membrane. The flux of MOF-membrane against the dye solutions containing rhodamine B (RhB), Congo red (CR), and their mixtures (RhB+CR) is estimated to be ∼39.9, 42.7 and 28.8 L/m2h, which is ∼3.6 times more than the pristine-membrane. Correspondingly, a rejection of ∼81.6, 77.6, and (87.2+79.2%) is estimated for RhB, CR and RhB+CR, respectively, which is ∼2.3 times higher the pristine-membrane. Furthermore, under sunlight irradiation, the MOF-membrane degrades ∼10.1, 7.1 and (7.3+4.2%) of RhB, CR and (RhB+CR) dyes, respectively. The parameters indicating regenerative efficiency, such as flux recovery ratio, reversible, irreversible, and total fouling are found to be enhanced for MOF-membranes compared to pristine-membrane. Overall, the incorporation of MOFs as additives enhances both separation and regeneration efficiency of membranes through photocatalytic process. This process holds promise as a reliable strategy for developing smart-membranes for energy-efficient real-time water treatment applications.