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 Various percentages of minimal-size ZnO and ZnO-GO for PSF membrane enhancement.  5 times reduction of ZnO usage with the introduction of GO nanosheets as support.  ZnO-GO composite is more hydrophilic compared to other GO-nanohybrid.  ZnO-GO membrane exhibits excellent antifouling and antibacterial properties.

Nanomaterials can be incorporated in the synthesis of membrane to obtain mixed-matrix membrane with marked improvement in properties and performance. However, stability and dispersion of the nanomaterials in the membrane matrix, as well as the need to use high ratio of nanomaterials for obvious improvement of membrane properties, remain a major hurdle for commercialization. Hence, this study aims to investigate the improvement of polyamide 6,6 membrane properties with the incorporation of silver nanoparticles decorated on graphene oxide (Ag-GO) nanoplates and at the same time focus is given to the issues above. Graphene oxide nanoplates were synthesized using the modified Hummers’ method and decorated with silver before embedded into the polyamide 6,6 matrix. Physicochemical characterizations were conducted on both nanoplates and the mixed-matrix Ag-GO polyamide 6,6 membrane. The issues of Ag agglomeration and leaching were not observed, which could be attributed to the decoration of Ag on GO that helped to disperse the nanomaterials and provided a better anchor point for the attachment of Ag nanoparticles. The synthesized membrane showed marked improvement regarding flux (135% increment) and antifouling (40% lower irreversible fouling), which could be ascribed to the more negative charge of membrane surface (−14 ± 6 to −31 ± 3.8 mV) and hydrophilicity (46% enhancement) of the membranes. With minimal embedment of Ag nanoparticles, the membrane showed superior antibacterial property where the E. coli bacteria could not form a single colony on the membrane surface. Overall, the decoration of Ag on GO nanoplates could be a promising approach to resolve the agglomeration and leaching issues as well as reduce the amount of precious Ag in the synthesis of Ag-GO polyamide 6,6 membrane.

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Incorporation of nanoparticles in membranes has recently been reported to lead to enhancement of the membrane performance for various applications. In this study, ZnO nanoparticles were synthesized via sol-gel method using zinc acetate and oxalic acid as starting materials. However, the influence of additive, in this case ethylene glycol (EG), on the size of ZnO nanoparticles produced was investigated. All diffraction peaks of XRD patterns indicated the wurtzite structure and the hexagonal phase of ZnO nanoparticles. Uniform spherical particle sizes with lower sizes and reduced agglomeration were observed when EG was used under the same experimental conditions. The particle size was found in the range of 20-30 nm when EG was used as compared to those without EG, which was between 50-60 nm. Dispersion property of the ZnO NPs was further verified by zetasizer analysis. Subsequent incorporation of the smaller size ZnO nanoparticles in membranes has shown improvement in the characteristics and performance of the membranes. Membranes incorporated with ZnO showed improved hydrophilicity and enhancement of membrane performance in terms of permeability, porosity, and rejection ability.

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