Enhancing Stability of Tannic Acid-Fe^III Nanofiltration Membrane for Water Treatment: Intercoordination by Metal–Organic Framework

Abstract

Tannic acid (TA)-Fe III nanofiltration (NF) membrane has been demonstrated to possess more favorable removal of trace organic contaminants (TrOCs) over the conventional polyamide NF membrane. However, the drawback of acid instability severely hinders the practical application of TA-Fe III NF membrane in the treatment of (weak) acidic wastewater containing TrOCs (e.g., pharmaceutical wastewater, surface water, and drinking water). Herein, we introduced the MIL-101(Cr) nanoparticle, a kind of metal−organic framework (MOF), into the TA-Fe III selective layer to enhance the membrane acid stability. The acid-tolerance parameter of MIL-101(Cr)-stabilized TA-Fe III membrane (TA-Fe III -MOF membrane, 12,000 ppm/s −1 ) was two orders of magnitude larger than that of the TA-Fe III membrane (50 ppm/s −1 ), and the TA-Fe III -MOF membrane can withstand acid treatment at pH = 4 for more than 30 days. Meanwhile, the TA-Fe III -MOF membrane displayed increased water permeance from 9.5 to 12.7 L/(m 2 •h•bar) after the MOF addition, without compromising the selectivity. The enhanced acid stability for the TA-Fe III -MOF membrane was ascribed to an intercoordination mechanism, where Fe III centers (from TA-Fe III complex) coordinated with −COOH groups (from terephthalic acid of MOF) and Cr III centers (from MOF) coordinated with −OH groups (from TA of TA-Fe III complex), which was verified by the density functional theory calculation. This study highlights a new approach for the development of a TA-Fe III -based NF membrane with markedly enhanced acid stability, which is important for its real application in wastewater treatment and water reuse.

Inhibiting Polyamide Intrusion of Thin Film Composite Membranes: Strategies and Environmental Implications

“…Tailoring polyamide membranes assisted by intrusion inhibition strategies could be a potential approach to significantly improve membrane permeance, thanks to lower transport distances and resistance. Indeed, the majority of research on substrate optimization (or interlayer) was still at the theoretical stage, , yet few of them have been applied in commercial applications. Our inhibitory strategies were prospectively feasible in practical production, which made it possible to manufacture the UPNF membranes with structurally optimized selective layers in one step production.…”

Understanding Rejection Mechanisms of Trace Organic Contaminants by Polyamide Membranes via Data-Knowledge Codriven Machine Learning

“…Efficient removal of trace organic contaminants (TrOCs) from diverse environmental matrices is of paramount importance. This urgency stems from their pervasive occurrence in freshwater systems − and concomitant potential threats to human health. , Polyamide (PA) nanofiltration (NF) and reverse osmosis (RO) membranes with subnanometer pores have emerged as important candidates for the TrOC removal. − However, the TrOC removal efficiency of current PA membranes is still unfavorable, as the fabrication standard of PA membranes was initially designed for salt removal performance. For example, the rejection of N -nitrosodimethylamine (NDMA) by the BW30 RO PA membrane was only ∼60% .…”