Enhancing H2O2 Tolerance and Separation Performance through the Modification of the Polyamide Layer of a Thin-Film Composite Nanofiltration Membrane by Using Graphene Oxide

Yi-Li Lin,Nai-Yun Zheng,Yu-Shen Chen

doi:10.3390/membranes11080592

Abstract

Through interfacial polymerization (IP), a polyamide (PA) layer was synthesized on the top of a commercialized polysulfone substrate to form a thin-film composite (TFC) nanofiltration membrane. Graphene oxide (GO) was dosed during the IP process to modify the NF membrane, termed TFC-GO, to enhance oxidant resistance and membrane performance. TFC-GO exhibited increased surface hydrophilicity, water permeability, salt rejection, removal efficiency of pharmaceutical and personal care products (PPCPs), and H2O2 resistance compared with TFC. When H2O2 exposure was 0–96,000 ppm-h, the surfaces of the TFC and TFC-GO membranes were damaged, and swelling was observed using scanning electron microscopy. However, the permeate flux of TFC-GO remained stable, with significantly higher NaCl, MgSO4, and PPCP rejection with increasing H2O2 exposure intensity than TFC, which exhibited a 3.5-fold flux increase with an approximate 50% decrease in salt and PPCP rejection. GO incorporated into a PA layer could react with oxidants to mitigate membrane surface damage and increase the negative charge on the membrane surface, resulting in the enhancement of the electrostatic repulsion of negatively charged PPCPs. This hypothesis was confirmed by the significant decrease in PPCP adsorption onto the surface of TFC-GO compared with TFC. Therefore, TFC-GO membranes exhibited superior water permeability, salt rejection, and PPCP rejection and satisfactory resistance to H2O2, indicating its great potential for practical applications.

Highlights

Membrane separation processes such as forward osmosis–nanofiltration (FO–NF), reverse osmosis–ultrafiltration (RO–UF), and membrane bioreactor (MBR) processes have been widely employed for removing suspended solids, emerging contaminants such as pharmaceuticals and personal care products (PPCPs) and persistent organic pollutants, microorganisms, and ion matter [1,2,3]
Few studies have systematically investigated the effects of TFC-Graphene oxide (GO) membranes on the rejection performance of other valence salts and emerging contaminants (i.e., PPCPs) and chemical resistance to oxidative cleaning agents (i.e., sodium hypochlorite (NaOCl) and H2O2 [18]) for long-term operation, and such properties are crucial for developing membranes suitable for practical applications
The TFC-GO membrane presented significantly broadened ridge–valley structures and a slight agglomeration of GO nanoparticles on the membrane surface when compared with the TFC membrane (Figure 2b)

Summary

Introduction

Membrane separation processes such as forward osmosis–nanofiltration (FO–NF), reverse osmosis–ultrafiltration (RO–UF), and membrane bioreactor (MBR) processes have been widely employed for removing suspended solids, emerging contaminants such as pharmaceuticals and personal care products (PPCPs) and persistent organic pollutants, microorganisms (e.g., bacteria and biofouling), and ion matter (e.g., monovalent, divalent, and large ions) [1,2,3]. The modification of PA layers to enhance both the contaminant removal and physicochemical resistance properties of oxidative cleaning reagents is essential and urgent. Lin et al indicated that adding 0.0125–0.0175 wt% of GO to the PA support layer of an FO membrane can reduce internal concentration polarization, enhance water flux, and maintain high rejection of salts and dyes [2,15]. Few studies have systematically investigated the effects of TFC-GO membranes on the rejection performance of other valence salts and emerging contaminants (i.e., PPCPs) and chemical resistance to oxidative cleaning agents (i.e., sodium hypochlorite (NaOCl) and H2O2 [18]) for long-term operation, and such properties are crucial for developing membranes suitable for practical applications

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Conclusion