Surface modification of thin-film nanocomposite forward osmosis membrane with super-hydrophilic MIL-53 (Al) for doxycycline removal as an emerging contaminant and membrane antifouling property enhancement

Abstract

• This work is the first study on the incorporation of MIL-53 (Al) into a TFN-FO membrane. • TFN 0.2 membrane showed the highest water flux without losing the selectivity. • Considerably boosted hydrophilicity (contact angle 20.6° vs. 80.4°) was attained. • Doxycycline rejection was obtained up to 99.73% in 2 h. • 96.67% flux recovery ratio was achieved in the filtration of BSA solution. As a contaminant of emerging concern, doxycycline is an antibiotic that has recently drawn rising attention due to its satisfactory outcomes for the treatment of COVID-19. In this study, a novel metal–organic framework thin-film nanocomposite forward osmosis (MOF-TFN FO) membrane was developed for doxycycline removal. The lack of applied hydraulic pressure in FO suggests an energy-efficient and low-cost process. A total of five composite membranes with different MIL-53 (Al) loadings (0, 0.1, 0.2, 0.3, and 0.5 wt%) were fabricated and characterized to assess the effect of MOF incorporation on the physicochemical properties of TFN membranes. Atomic force microscopy (AFM) and field emission scanning electron microscopy (FESEM) analysis implied that incorporating MIL-53 (Al) in the polyamide selective layer affects the membrane morphology. Water contact angle measurements indicated significant augmentation in the hydrophilicity of modified membranes (20.6° for the optimally modified membrane vs. 80.4° for the unmodified membrane) owing to the increased hydroxyl group in the membrane selective layer. Due to the reduced structural parameter, the optimized membrane exhibited 94.31% enhanced water flux than the unmodified membrane without losing the selectivity. Also, the fouling experiments with organic foulant allude to the prominent antifouling property of this modified membrane with a 96.67% flux recovery ratio. More notably, the optimized membrane could maintain a high and stable rejection for doxycycline (>98.5%) for 10 h due to its size exclusion and adsorption properties. Our findings reveal the promising results of TFN FO membranes containing MOFs for antibiotics removal, which is not addressed sufficiently in the literature.