A metal organic framework-ultrafiltration hybrid system for removing selected pharmaceuticals and natural organic matter

In this study, we combined metal organic frameworks (MOFs) with ultrafiltration (UF) hybrid systems (MOF-UF) to treat selected pharmaceutically active compounds (PhACs), including ibuprofen and 17α-ethinyl estradiol, and natural organic matter (NOM) (humic acid and tannic acid; ratios of 10:0, 5:5, and 0:10). Due to the high tunable porosity of MOFs, these materials have strong potential for removing contaminants and reducing fouling in adsorbent-UF hybrid systems. The average retention rate of PhACs in MOF-UF (53.2%) was enhanced relative to the UF only (36.7%). The average retention rate of NOM in the MOF-UF (86.1%) was higher than that with UF only (75.7%). Also, the average normalized flux of NOM in the MOF-UF (0.79) was better than that with UF only (0.74). This is because the PhACs were effectively adsorbed on the MOF due to their strong porous characteristics. We compared MOF-UF and powdered activated carbon-UF (PAC-UF) systems in terms of retention rates and flux decline. The average retention rates for the MOF-UF were higher relative to PAC-UF, by 4.6% for PhACs and 6.9% for NOM. However, although the normalized flux in the MOF-UF was better than that in the PAC-UF, for both PhACs and NOM, severe flux decline for NOMs was seen for with the MOF-UF and PAC-UF. We evaluated the effects of NOM with respect to fouling by applying a resistance-in-series model and found that fouling was dominantly affected by the molecular sizes of the solutes in the solution.