Versatile Surface Modification of TFC Membrane by Layer-by-Layer Assembly of Phytic Acid–Metal Complexes for Comprehensively Enhanced FO Performance

Abstract

Polyamide TFC membranes are widely applied in membrane-based water treatment but generally suffer various fouling problems. In this work, the layer-by-layer assembly of phytic acid (PA) and metal ions (M) is constructed on the surface TFC membrane for the first time, to improve the bio/organic fouling resistances and separation performance of TFC membranes simultaneously. The PA molecule with six phosphonic acid groups of strong chelation ability acts as the organic ligand, and the metal ion acts as the inorganic cross-linker, inducing the assembly of hydrophilic and antibacterial PA-M (Ag or Cu) complexes on the TFC membrane surface. Various characterizations including FTIR, XPS, SEM, AFM, and EDX are employed to confirm the successful and uniform modification of PA-M. FO performance of the PA-M modified TFC membranes, i.e., TFC_PA-Ag and TFC_PA-Cu, is optimized by varying PA concentration and assembly cycles, where the water flux can be improved by 57% and 68%, respectively, without compromising the membrane selectivity. Additionally, the PA-M modification improves the biofouling and organic fouling resistances of the TFC membrane remarkably, owing to the enhanced antibacterial ability and hydrophilicity. The modified TFC membranes are also proven to show the excellent stability by the quantitative release test.

A Dopamine/Tannic-Acid-Based Co-Deposition Combined with Phytic Acid Modification to Enhance the Anti-Fouling Property of RO Membrane

“…The peak appearing at 717.7 eV belongs to the satellite peak of the Fe element [ 38 ]. From the spectrum of P 2p ( Figure 2 e), the presence of P = O (132.8 eV), P-OH (133.4 eV), and P-O-Fe (134.2 eV) are presented, confirming that PhA was successfully grafted onto the membrane through the Fe 3+ complexation [ 30 ].…”

“…Compared with the weak acidic phenolic hydroxyl groups, strong phosphonic acids have a higher degree of ionization, showing more affinity toward water molecules. As one of the non-toxic and natural phosphonic acids, phytic acids (PhA) have attracted extensive attention for enhancing the anti-fouling properties of membranes [ 30 , 31 ]. A phytic acid molecule contains six electronegative phosphate groups which can chelate a variety of metal ions; the PhA-metal complex system provides a new strategy for surface modification of membranes [ 32 ].…”

“…A phytic acid molecule contains six electronegative phosphate groups which can chelate a variety of metal ions; the PhA-metal complex system provides a new strategy for surface modification of membranes [ 32 ]. For example, Xiong [ 30 ] and Qi [ 33 ] constructed PhA-metal complexes through a layer-by-layer self-assembly method to obtain a modified osmosis membrane with fine anti-fouling properties. However, due to the lack of strong complexing sites, it is difficult to introduce the PhA groups onto the membrane surface directly and easily.…”

Antibiofouling Thin‐Film Nanocomposite Membranes for Sustainable Water Purification

“…To compare the antibacterial behaviors of the Cu NPs and Ag NPs, as illustrated in Figure 5, Ag + and Cu 2+ were used to modify the TFC membranes (TFC_PA-Ag and TFC_PA-Cu). [97] The results of the inhibition zone test showed that the inhibitory effects of the TFC_PA-Ag membrane against E. coli were significantly larger than those of the TFC_PA-Cu membrane. Moreover, the number of E. coli was significantly higher for TFC_PA-Cu, despite better hydrophilicity.…”

“…Antibiofouling properties of TFC, TFC_PA-Ag, and TFC_PA-Cu membranes: a) the inhibition zone test against E. coli and b) SEM images of different TFC membranes after exposure to E. coli suspension. Reproduced with permission [97]. Copyright 2019, American Chemical Society.…”