Coupling thin film nanofiltration membrane and photocatalyst for the removal of antidepressant drugs from aqueous solutions

Metal–organic frameworks (MOFs) have a high capability for the structure of membranes and photocatalysts to remove organic pollutants from water. In this study, a nanofiltration/photocatalysis coupled system was used to remove three antidepressant drugs—fluoxetine hydrochloride (FLX), sertraline hydrochloride (STL), and paroxetine hydrochloride (PRX)—from water. The thin film nanocomposite (TFN) nanofiltration membranes were loaded with varying amounts of NH2-MIL-101 (Fe) to filter the selected antidepressants under initial concentration of 10 mgL−1. The concentrated pharmaceuticals from the rejected stream of the nanofiltration system were then fed into the photocatalysis process. The NH2-MIL-101 (Fe)/TiO2 nanofibrous photocatalyst, in the presence of peroxymonosulfate (PMS) and solar light irradiation, was used to remove the antidepressants. After 48 h, the permeation fluxes and rejection percentages for FLX, PRX, and STL were 37.1 Lm−2.h−1 & 98.52%, 35.1 Lm−2.h−1 & 98.12%, and 37.8 Lm−2.h−1 & 98.74%, respectively. The final concentrations of FLX, PRX, and STL in the rejected stream after 48 h of membrane filtration experiment were 37.02, 35.06, and 37.80 mgL−1, respectively. The photocatalytic degradation efficiency of FLX, STL, and PRX using 0.5 gL−1 NH2-MIL-101 (Fe)/TiO2 nanofibrous photocatalyst, in the presence of 2 mM PMS and solar light irradiation, was 99.68%, 99.35%, and 99.21% during 30 min at a pH of 9. These results demonstrate that the coupling of membrane separation and photocatalysis processes, using MOFs-based TFN nanofiltration membranes/photocatalyst, is an effective strategy for treating pharmaceutical wastewater.