Polyethersulfone ultrafiltration membrane modified with amine-functionalized zeolitic imidazole framework decorated graphene oxide for antibacterial functionality
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Date
2022
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Publisher
Universiti Teknologi Malaysia
Abstract
Biofouling is a critical issue in membrane separation because it leads to a decline in the membrane permeability , shortens the membrane lifespan and increases the operating costs. Introducing nanomaterials with antibacterial properties into the membrane becomes preferable as it is not only improving the hydrophilicity of the membrane but also effectively preventing initial cell adhesion and growth onto the membrane. This study aims to develop polyether sulfone based hollow fibre ultrafiltration (PES-UF) membranes with antibacterial functionality by incorporating the amine-modified zeolitic imidazole framework-8 decorated graphene oxide (ZGO-NH). In the first stage of this study, zeolitic imidazole framework-8 decorated graphene oxide (ZGO) was firstly synthesized and modified with ammonia solution to produce ZGO-NH nanocomposite. All synthesized nanomaterials are characterized in terms of structural morphology, elemental analysis, physicochemical properties, and antibacterial activity. The characterization of ZGO showed that ZIF-8 was well decorated on graphene oxide sheets, and the ZIF-8 framework was not distorted after the modifications. The ZGO nanocomposites have been successfully functionalized with amine to further enhance the antibacterial activity. Based on an antibacterial assay using the minimum inhibitory concentration (MIC) and disc diffusion test (DDT), the ZGO-NH samples have higher antibacterial activity against Escherichia coli (ATCC 11229) and Staphylococcus aureus (ATCC 6538) compared to the ZGO samples. Results also showed that the antibacterial effects of ZGO-NH samples were more pronounced against S. aureus (a gram-positive bacteria) than E. coli (a gram-negative bacteria). In addition, different weight percentages of ZGO-NH (0.3, 0.5, 1.0, and 2.0 wt%) as an antibacterial agent was incorporated into the PES hollow membrane. The prepared membranes were characterized for their hydrophilicity, morphological study, and surface roughness to investigate the impact of the membrane functionalization on the separation and antibacterial performance. The results obtained revealed the presence of abundant oxygenated groups from GO and the amine groups significantly influence the overall membrane properties. The highest pure water flux, 98.95 L/m2·h, was achieved from the membrane incorporated with 1.0 wt% of ZGO-NH due to an increase in hydrophilicity, the reduction in top skin layer membrane thickness, and low surface roughness. The modified membrane also shows an excellent antibacterial impact of 81.1% and 85.7% against E. coli and S. aureus. The stability of ZGO-NH nanomaterials in the modified membrane in the leaching study was stable, with the amount of leached Zn2+ ions being negligible after 24 hr of continuous crossflow filtration. The outcome of this study has found a novel and promising antibacterial functionality of the membrane due to the synergistic effect of ZIF-8, GO, and amine groups responsible for long-term antibacterial effects for membrane biofouling control in water and wastewater treatment.
Description
Thesis (PhD. (Chemical Engineering))
Keywords
Fouling, Membrane separation, Anti-infective agents—Testing