Boosting the Performance of Nanofiltration Membranes in Removing Organic Micropollutants: Trade-Off Effect, Strategy Evaluation, and Prospective Development

Abstract

In view of the high risks brought about by organic micropollutants (OMPs), nanofiltration (NF) processes have been playing a vital role in advanced water and wastewater treatment, owing to the high membrane performance in rejection of OMPs, permeation of water, and passage of mineral salts. Though numerous studies have been devoted to evaluating and technically enhancing membrane performance in removing various OMPs, the trade-off effect between water permeance and water/OMP selectivity for state-of-the-art membranes remains far from being understood. Knowledge of this effect is significant for comparing and guiding membrane development works toward cost-efficient OMP removal. In this work, we comprehensively assessed the performance of 88 NF membranes, commercialized or newly developed, based on their water permeance and OMP rejection data published in the literature. The effectiveness and underlying mechanisms of various modification methods in tailoring properties and in turn performance of the mainstream polyamide (PA) thin-film composite (TFC) membranes were quantitatively analyzed. The trade-off effect was demonstrated by the abundant data from both experimental measurements and machine learning-based prediction. On this basis, the advancement of novel membranes was benchmarked by the performance upper-bound revealed by commercial membranes and lab-made PA membranes. We also assessed the potentials of current NF membranes in selectively separating OMPs from inorganic salts and identified the future research perspectives to achieve further enhancement in OMP removal and salt/OMP selectivity of NF membranes.

Molecular Design of the Polyamide Layer Structure of Nanofiltration Membranes by Sacrificing Hydrolyzable Groups toward Enhanced Separation Performance

“…This complied well with the narrowing of membrane pore size and enhancement of membrane surface negative charges. The rejection behavior for TrOCs was different from that for the reference neutral solutes, which could be greatly influenced by the physicochemical properties of the TrOCs themselves and the active layer. − When the M PA membrane was tested, the rejections of the six TrOCs were within 41.2–83.8%, with the lowest rejection for carbamazepine which has a low MW of 236.3 Da and relatively high hydrophobicity. , In comparison, when the M MPA membrane was tested, the rejections of the six TrOCs were within 61.5–81.7%, with the lowest rejection for atenolol, due to its low MW and strong electrostatic attraction with the negatively charged membrane surface. It seems that the M MPA‑0.66 membrane could achieve the most-balanced rejections of the six TrOCs, which also demonstrated the lowest rejections of hardness ions among the prepared membranes (Figure B).…”

“…53−58 When the M PA membrane was tested, the rejections of the six TrOCs were within 41.2−83.8%, with the lowest rejection for carbamazepine which has a low MW of 236.3 Da and relatively high hydrophobicity. 59,60 In comparison, when the M MPA membrane was tested, the rejections of the six TrOCs were within 61.5−81.7%, with the lowest rejection for atenolol, due to its low MW and strong electrostatic attraction with the negatively charged membrane surface. It seems that the M MPA-0.66 membrane could achieve the most-balanced rejections of the six TrOCs, which also demonstrated the lowest rejections of hardness ions among the prepared membranes (Figure 4B).…”

Making waves: Why do we need ultra-permeable nanofiltration membranes for water treatment?

“…Taking water reuse as an example, the removal of harmful organic micropollutants is of critical importance to protect the public health. While this critical aspect is often neglected in traditional membrane development, some studies report the feasibility of simultaneous enhancement of pollutant removal and water permeance–revealing the huge room for future membrane development and optimization ( Guo et al., 2022 ; Liu et al., 2022 ; Yang et al., 2020 ).…”

“…Nevertheless, others are of the opinion that high water permeance plays a far less important role than selectivity ( Shi et al., 2017 ; Werber et al., 2016a ). Although this concern is legitimate for membrane processes involving high transmembrane osmotic pressure difference (Δ π ) such as RO-based seawater desalination ( Cohen-Tanugi et al., 2014 ; Elimelech and Phillip, 2011 ; Patel et al., 2020 ; Shi et al., 2017 ; Werber et al., 2016a , 2016b ; Yang et al., 2021 ), many NF applications involves relatively low Δ π ( Guo et al., 2021 ; Liu et al., 2022 ; Shao et al., 2022 ; Wang et al., 2022 ; Yang et al., 2021 ; Zhao et al., 2021 ), which leaves sufficient room for energy savings. Another common opinion is that, in view of the membrane permeance-selectivity tradeoff ( Fig.…”

APTMS‐Modified Silica as a Thin‐Film Nanocomposite Forward Osmosis Membranes: Towards Enhanced Selectivity and Dye Rejection Stability for Congo Red and Rhodamine B

“…These membranes exhibit good mechanical strength and effectively mitigate the impact of reverse solute flux and concentration polarization. [8,9] Furthermore, the widely used thin-film composite (TFC) and thin-film nanocomposite (TFN) membranes have demonstrated capabilities in addressing various types of contamination, [10] including heavy metals, emerging pollutants, and dye contamination. Karki et al [11] employed TFN membranes prepared through vapor phase interfacial polymerization for the removal of heavy metal ions.…”