TWO-DIMENSIONAL NANOSTRUCTURE-BASED ANTIFOULING MEMBRANES FOR  WATER FILTRATION

Iftaykhairul   Alam

Fouling is the accumulation of biofilms, salts, and many organic foulants like proteins, polysaccharides, and natural organic matter on membrane surfaces during membrane separation processes. Considerable efforts have been put towards mitigating fouling problems, which include pretreatment of the feed, coating thin polymer film on the membrane surface, or grafting polymer chains on the surfaces. However, commercially available polymeric membranes still suffer significantly from fouling due to their hydrophobic nature, which increases charge interaction between the membrane surface and diverse foulants. In recent years, two-dimensional (2D) graphene-based nanomaterials including graphene oxide (GO) and reduced graphene oxide (rGO) have shown great potential for modification of membrane surfaces because of their antimicrobial properties. While graphene-based materials have been extensively studied, Molybdenum disulfide (MoS2), a member of the emerging 2D nanomaterial class of transition metal dichalcogenides, is less well-understood but has gained attention due to its unique electrical, physicochemical and mechanical properties. Despite the significant research that has focused on MoS2 for application in electronics, catalysis, biomedical, and energy-related fields, its use as an antifouling material for membrane applications has not been extensively explored. From this study, it was found that MoS2 performs significantly better than GO under different fouling conditions due to the smooth surface and absence of functional groups on MoS2. Unlike GO, application of a small external potential (± 0.5V Ag/AgCl) was found to be effective in delaying the attachment of protein foulant onto MoS2-functionalized surface due to its better conductivity. The MoS2 membranes also exhibited five times higher water permeability than the GO functionalized membranes as oxidized regions of GO significantly impedes water transport through its nanochannels. The combination of GO and MoS2 in a composite membrane resulted in excellent salt rejection (>70%) from synthetic wastewater while maintaining suitable water permeability. The salt rejection performance was further improved by the increased stability and non-swelling behavior of the GO-MoS2 composites. These nanocomposite membranes could be used for modern industrial wastewater processing, recycling, and reuse to meet the rising water demand. The addition of these materials would also benefit future research on membrane modifications for fouling control and desalination.

TWO-DIMENSIONAL NANOSTRUCTURE-BASED ANTIFOULING MEMBRANES FOR WATER FILTRATION

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