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A new nano-engineered hierarchical membrane for concurrent removal of surfactant and oil from oil-in-water nanoemulsion.

Qin D, Liu Z, Bai H, Sun DD, Song X - Sci Rep (2016)

Bottom Line: The physical and chemical properties of the overall membrane, including wettability, surface roughness, electric charge, thickness and structures, are delicately tailored through a nano-engineered fabrication process, that is, graphene oxide (GO) nanosheet assisted phase inversion coupled with surface functionalization.Compared with the membrane fabricated by conventional phase inversion, this novel membrane has four times higher water flux, significantly higher rejections of both oil (~99.9%) and surfactant (as high as 93.5%), and two thirds lower fouling ratio when treating surfactant stabilized oil-in-water nanoemulsion.Due to its excellent performances and facile fabrication process, this nano-engineered membrane is expected to have wide practical applications in the oil/water separation fields of environmental protection and water purification.

View Article: PubMed Central - PubMed

Affiliation: Energy Research Institute @ NTU, Interdisciplinary Graduate School, Nanyang Technological University, 639798, Singapore.

ABSTRACT
Surfactant stabilized oil-in-water nanoemulsions pose a severe threat to both the environment and human health. Recent development of membrane filtration technology has enabled efficient oil removal from oil/water nanoemulsion, however, the concurrent removal of surfactant and oil remains unsolved because the existing filtration membranes still suffer from low surfactant removal rate and serious surfactant-induced fouling issue. In this study, to realize the concurrent removal of surfactant and oil from nanoemulsion, a novel hierarchically-structured membrane is designed with a nanostructured selective layer on top of a microstructured support layer. The physical and chemical properties of the overall membrane, including wettability, surface roughness, electric charge, thickness and structures, are delicately tailored through a nano-engineered fabrication process, that is, graphene oxide (GO) nanosheet assisted phase inversion coupled with surface functionalization. Compared with the membrane fabricated by conventional phase inversion, this novel membrane has four times higher water flux, significantly higher rejections of both oil (~99.9%) and surfactant (as high as 93.5%), and two thirds lower fouling ratio when treating surfactant stabilized oil-in-water nanoemulsion. Due to its excellent performances and facile fabrication process, this nano-engineered membrane is expected to have wide practical applications in the oil/water separation fields of environmental protection and water purification.

No MeSH data available.


Related in: MedlinePlus

The structure of membrane selective layer.(a) P membrane, (b) GO-P membrane, (c) GO-P-S membrane. (a-1~c-1) AFM images of membrane topography. (a-2~c-2) FESEM images of membrane top surface, scale bar 300 nm; the inserted figures are enlarged FESEM images of membrane top surface, scale bar 150 nm. (d) Optical photo of GO-P-S membrane which demonstrates its outstanding mechanical flexibility.
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f1: The structure of membrane selective layer.(a) P membrane, (b) GO-P membrane, (c) GO-P-S membrane. (a-1~c-1) AFM images of membrane topography. (a-2~c-2) FESEM images of membrane top surface, scale bar 300 nm; the inserted figures are enlarged FESEM images of membrane top surface, scale bar 150 nm. (d) Optical photo of GO-P-S membrane which demonstrates its outstanding mechanical flexibility.

Mentions: Guided by the above design rationale, the hierarchically-structured membrane is synthesized through GO assisted phase inversion coupled with delicate surface functionalization towards the complete separation of nanoemulsion. This nano-engineered membrane is coded as “GO-P-S” membrane; while for the comparison purpose, GO assisted phase inversion constructed membrane without surface functionalization is coded as “GO-P” membrane, and conventional phase inversion constructed membrane with neither GO nano-engineering nor surface functionalization is coded as “P” membrane, respectively. Here, GO nanosheet (Fig. S3) is chosen to adjust the phase inversion process so as to tailor the structure of resultant membrane. The mechanism is the superhydrophilicity of GO nanosheet can accelerate phase inversion process through inducing a faster exchange of water intrusion with solvent extrusion4142. As the result of GO nano-engineering, phase inversion constructed membrane is tuned to be more porous (Fig. 1a,b). Observed by FESEM image, the average pore radius of membrane selective layer (membrane top surface) r1 is enlarged from ~8 nm (Fig. 1a-2) to ~16 nm (Fig. 1b-2), accompanied by the emergence of a few big pores as large as 80 nm (Fig. 1b-2). More importantly, the pore number density of selective layer (N1) is increased remarkably from 120 μm−2 to 410 μm−2 owing to the nano-engineering by GO sheet. Simultaneously, an ultrathin nanoporous selective layer is generated as the result of GO nano-engineering, with the thickness of selective layer (L1) reduced by ~45% from 880 nm (Fig. 2a-1) to 490 nm (Fig. 2b-1). Meanwhile, the average pore radius of membrane bottom surface is enlarged from ~0.3 μm (Fig. 2a-2) to ~2.0 μm (Fig. 2b-2), which indicates the interconnectivity of pores in membrane cross-section gets improved (τ gets decreased).


A new nano-engineered hierarchical membrane for concurrent removal of surfactant and oil from oil-in-water nanoemulsion.

Qin D, Liu Z, Bai H, Sun DD, Song X - Sci Rep (2016)

The structure of membrane selective layer.(a) P membrane, (b) GO-P membrane, (c) GO-P-S membrane. (a-1~c-1) AFM images of membrane topography. (a-2~c-2) FESEM images of membrane top surface, scale bar 300 nm; the inserted figures are enlarged FESEM images of membrane top surface, scale bar 150 nm. (d) Optical photo of GO-P-S membrane which demonstrates its outstanding mechanical flexibility.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4834549&req=5

f1: The structure of membrane selective layer.(a) P membrane, (b) GO-P membrane, (c) GO-P-S membrane. (a-1~c-1) AFM images of membrane topography. (a-2~c-2) FESEM images of membrane top surface, scale bar 300 nm; the inserted figures are enlarged FESEM images of membrane top surface, scale bar 150 nm. (d) Optical photo of GO-P-S membrane which demonstrates its outstanding mechanical flexibility.
Mentions: Guided by the above design rationale, the hierarchically-structured membrane is synthesized through GO assisted phase inversion coupled with delicate surface functionalization towards the complete separation of nanoemulsion. This nano-engineered membrane is coded as “GO-P-S” membrane; while for the comparison purpose, GO assisted phase inversion constructed membrane without surface functionalization is coded as “GO-P” membrane, and conventional phase inversion constructed membrane with neither GO nano-engineering nor surface functionalization is coded as “P” membrane, respectively. Here, GO nanosheet (Fig. S3) is chosen to adjust the phase inversion process so as to tailor the structure of resultant membrane. The mechanism is the superhydrophilicity of GO nanosheet can accelerate phase inversion process through inducing a faster exchange of water intrusion with solvent extrusion4142. As the result of GO nano-engineering, phase inversion constructed membrane is tuned to be more porous (Fig. 1a,b). Observed by FESEM image, the average pore radius of membrane selective layer (membrane top surface) r1 is enlarged from ~8 nm (Fig. 1a-2) to ~16 nm (Fig. 1b-2), accompanied by the emergence of a few big pores as large as 80 nm (Fig. 1b-2). More importantly, the pore number density of selective layer (N1) is increased remarkably from 120 μm−2 to 410 μm−2 owing to the nano-engineering by GO sheet. Simultaneously, an ultrathin nanoporous selective layer is generated as the result of GO nano-engineering, with the thickness of selective layer (L1) reduced by ~45% from 880 nm (Fig. 2a-1) to 490 nm (Fig. 2b-1). Meanwhile, the average pore radius of membrane bottom surface is enlarged from ~0.3 μm (Fig. 2a-2) to ~2.0 μm (Fig. 2b-2), which indicates the interconnectivity of pores in membrane cross-section gets improved (τ gets decreased).

Bottom Line: The physical and chemical properties of the overall membrane, including wettability, surface roughness, electric charge, thickness and structures, are delicately tailored through a nano-engineered fabrication process, that is, graphene oxide (GO) nanosheet assisted phase inversion coupled with surface functionalization.Compared with the membrane fabricated by conventional phase inversion, this novel membrane has four times higher water flux, significantly higher rejections of both oil (~99.9%) and surfactant (as high as 93.5%), and two thirds lower fouling ratio when treating surfactant stabilized oil-in-water nanoemulsion.Due to its excellent performances and facile fabrication process, this nano-engineered membrane is expected to have wide practical applications in the oil/water separation fields of environmental protection and water purification.

View Article: PubMed Central - PubMed

Affiliation: Energy Research Institute @ NTU, Interdisciplinary Graduate School, Nanyang Technological University, 639798, Singapore.

ABSTRACT
Surfactant stabilized oil-in-water nanoemulsions pose a severe threat to both the environment and human health. Recent development of membrane filtration technology has enabled efficient oil removal from oil/water nanoemulsion, however, the concurrent removal of surfactant and oil remains unsolved because the existing filtration membranes still suffer from low surfactant removal rate and serious surfactant-induced fouling issue. In this study, to realize the concurrent removal of surfactant and oil from nanoemulsion, a novel hierarchically-structured membrane is designed with a nanostructured selective layer on top of a microstructured support layer. The physical and chemical properties of the overall membrane, including wettability, surface roughness, electric charge, thickness and structures, are delicately tailored through a nano-engineered fabrication process, that is, graphene oxide (GO) nanosheet assisted phase inversion coupled with surface functionalization. Compared with the membrane fabricated by conventional phase inversion, this novel membrane has four times higher water flux, significantly higher rejections of both oil (~99.9%) and surfactant (as high as 93.5%), and two thirds lower fouling ratio when treating surfactant stabilized oil-in-water nanoemulsion. Due to its excellent performances and facile fabrication process, this nano-engineered membrane is expected to have wide practical applications in the oil/water separation fields of environmental protection and water purification.

No MeSH data available.


Related in: MedlinePlus