158
C. Sun et al.
Although the NPG membranes work very well in the laboratory, many challenges
are still faced to make these membranes practicable in the industry. The main challenges for the realization of industrial-scale NPG membranes include fabrication of
large-scale NPG sheets with a high mechanical stability and free of intricate defects
and artificial damages, transfer of graphene sheets to a supporting substrate with no
damage, and generation of high-density pores in the graphene sheets with precisely
controlled sizes. All of these challenges should be the main concerns of future studies,
which are expected to fill the gaps between laboratory study and industrial application
of graphene-based membranes. We hope that the continuous efforts on the graphenebased membranes can not only make such separation membranes practicable but
also stimulate the applications of graphene sheets in energy harvesting and storage,
bioengineering and so on [77], because graphene sheets have a great application
prospect in the above fields apart from the separation science and technology. For
example, graphene is a good hydrogen production material for its excellent proton
conductance and electron transport efficiency; graphene-related materials can be
employed in hydrogen storage for their low gravimetric density and strong hydrogen
affinity; graphene can be used in supercapacitors for its large specific area and high
electrical conductivity; NPG is also very promising as DNA sequencing tools for its
intrinsic solid-state nanopores. In summary, graphene-based membranes have shed
a bright light, but many efforts must be devoted to solve these challenges faced
currently.
5 Conclusions
Graphene has shed light on the two-dimensional high-permeability separation
membranes in the fields of water purification due to its atomic thickness. NPG as one
of the graphene-based membranes has demonstrated to be very promising for water
purification based on the mechanisms of RO and electrodialysis. Recently, many theoretical and experimental works were conducted on the NPG-based membranes for
water purification. The separation performances, underlying mechanisms, membrane
fabrication methods of these membranes were discussed in detail. In this chapter,
we summary the representative experimental and simulation works on the NPG
membranes both on the RO and electrodialysis. Apart from the solution separation,
the NPG-based membranes are expected to have a great application prospect in other
ion-related applications, such as energy harvesting from the selective ion transport
through membranes, energy storage based on the supercapacitors with nanostructured
materials, etc. For example, the NPG-related materials have shown promises in power
generation from the salinity gradient based on the reverse electrodialysis with selective ion transport. It is hoped that the researches on the NPG-based membranes can
not only make the two-dimensional separation membranes more and more promising
but also promote the developments of other ion-related applications.
C. Sun et al.
Although the NPG membranes work very well in the laboratory, many challenges
are still faced to make these membranes practicable in the industry. The main challenges for the realization of industrial-scale NPG membranes include fabrication of
large-scale NPG sheets with a high mechanical stability and free of intricate defects
and artificial damages, transfer of graphene sheets to a supporting substrate with no
damage, and generation of high-density pores in the graphene sheets with precisely
controlled sizes. All of these challenges should be the main concerns of future studies,
which are expected to fill the gaps between laboratory study and industrial application
of graphene-based membranes. We hope that the continuous efforts on the graphenebased membranes can not only make such separation membranes practicable but
also stimulate the applications of graphene sheets in energy harvesting and storage,
bioengineering and so on [77], because graphene sheets have a great application
prospect in the above fields apart from the separation science and technology. For
example, graphene is a good hydrogen production material for its excellent proton
conductance and electron transport efficiency; graphene-related materials can be
employed in hydrogen storage for their low gravimetric density and strong hydrogen
affinity; graphene can be used in supercapacitors for its large specific area and high
electrical conductivity; NPG is also very promising as DNA sequencing tools for its
intrinsic solid-state nanopores. In summary, graphene-based membranes have shed
a bright light, but many efforts must be devoted to solve these challenges faced
currently.
5 Conclusions
Graphene has shed light on the two-dimensional high-permeability separation
membranes in the fields of water purification due to its atomic thickness. NPG as one
of the graphene-based membranes has demonstrated to be very promising for water
purification based on the mechanisms of RO and electrodialysis. Recently, many theoretical and experimental works were conducted on the NPG-based membranes for
water purification. The separation performances, underlying mechanisms, membrane
fabrication methods of these membranes were discussed in detail. In this chapter,
we summary the representative experimental and simulation works on the NPG
membranes both on the RO and electrodialysis. Apart from the solution separation,
the NPG-based membranes are expected to have a great application prospect in other
ion-related applications, such as energy harvesting from the selective ion transport
through membranes, energy storage based on the supercapacitors with nanostructured
materials, etc. For example, the NPG-related materials have shown promises in power
generation from the salinity gradient based on the reverse electrodialysis with selective ion transport. It is hoped that the researches on the NPG-based membranes can
not only make the two-dimensional separation membranes more and more promising
but also promote the developments of other ion-related applications.