Abstract
A simple and novel strategy of superhydrophilic-superhydrophobic Janus membrane was provided here to deal with the increasingly serious oil-water separation problem, which has a very bad impact on environmental pollution and resource recycling. The Janus membrane of cPVA-PVDF/PMMA/GO with opposite hydrophilic and hydrophobic properties was prepared by layer-by-layer electrospinning. The structure of the Janus membrane is as follows: firstly, the mixed solution of polyvinylidene fluoride (PVDF), polymethylmethacrylate (PMMA) and graphene oxide (GO) was electrospun to form a hydrophobic layer, then polyvinyl alcohol (PVA) nanofiber was coated onto the hydrophobic membrane by layer-by-layer electrospinning to form a composite membrane, and finally, the composite membrane was crosslinked to obtain a Janus membrane. The addition of GO can significantly improve the hydrophobicity, mechanical strength and stability of the Janus membrane. In addition, the prepared Janus membrane still maintained good oil-water separation performance and its separation efficiency almost did not decrease after many oil-water separation experiments. The flux in the process of oil-water separation can reach 1909.9 L m−2 h−1, and the separation efficiency can reach 99.9%. This not only proves the separation effect of the nanocomposite membrane, but also shows its high stability and recyclability. The asymmetric Janus membrane shows good oil-water selectivity, which gives Janus membrane broad application prospects in many fields.
Highlights
The frequent occurrence of oil spills and the discharge of oily wastewater have made the problem of oil-water separation increasingly serious
Only adding 1% graphene oxide (GO) dispersions is the best option to prepare polyvinylidene fluoride (PVDF)/PMMA/GO hydrophobic side. It can be proved from the cross-section that the two membranes are compounded together, and the hydrophilic cross-linked PVA (cPVA) nanofibers cover the hydrophobic layer PVDF/PMMA/GO to form an interwoven nanofiber layer with a reduced pore size (Figure 2h)
We found that the prepared cPVA-PVDF/PMMA/GO Janus membranes by layer-by-layer electrospinning have an obvious large contact angle, which proves the superhydrophobicity of the prepared material
Summary
The frequent occurrence of oil spills and the discharge of oily wastewater have made the problem of oil-water separation increasingly serious. Electrospinning can produce nanofibers with special structures with low cost and relatively high productivity, especially ultra-fine fiber materials with large specific surface area and long length; it has broad prospects in many fields, such as immunoassay, catalysis, tissue engineering, sensors, composite reinforcement, adsorption and filtration, etc. Janus membrane is a general term for membranes with opposite properties, such as composition, morphology, wettability, surface charge, and so on. The biggest advantage of the Janus membrane is that it can meet the needs of two contradictory properties in a certain application at the same time. This concept has great applications in many fields, such as oil-water separation, one-way ion channel, fog collection, contact enzyme membrane reactor, solar distillation, etc. This concept has great applications in many fields, such as oil-water separation, one-way ion channel, fog collection, contact enzyme membrane reactor, solar distillation, etc. [14,15,16,17,18]
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