48
A. S. Kazemi and M. A. Abdol
(i) their high permeance could enable higher energy efficiency and compact,
high-productive membrane separation systems [68, 85, 86].
(ii) their robustness due to high chemical resistance and mechanical strength
could prove useful for operation under harsh conditions, e.g., better withstand chlorine, allow more aggressive cleaning procedures [86], overcome
challenges of aging, compaction and influence of solvents in organic solvent
nanofiltration [7].
(iii) in case of providing universal size-based rejection independent of the solute,
it would benefit applications involving a diversity of solutes, e.g., removal
of persistent organic pollutants and boron from seawater or in chemical
processing [1, 3, 7, 14, 87].
(iv) their flatness could overcome fouling [20].
Built on what is explained so far, an ideal RO membrane based on nano-porous
atomically thin materials would be extremely flexible and mechanically stable to
fit into the spiral-wound RO modules for the highest efficiency. It would also be
extremely flat to mitigate fouling, and it would be decorated with pores of ideal
nano-sizes and distributions to break permeability–selectivity trade-off. Besides, it
would be extremely thin, to maintain high water permeation as shown schematically
in Fig. 2.
Another important aspect of the RO membrane is the substrate underneath the
active layer or the so-called ‘support layer’. The principal role of the substrate is
to provide mechanical support for the active layer via bearing most of the hydraulic
load and at the same time, distributing the pressure from the water onto patches of the
active layer. However, the substrate has a minor direct role in the salt rejection process,
while water simply percolates through its pore network after permeating through the
active layer [88–90]. In conventional TFC membranes, the active layer (typically
composed of polyamide) bears the salt rejection role and extends 100−200 nm in
thickness [91].
Fig. 2 Ideal RO membrane based on supreme characteristics of nano-porous atomically thin
materials
A. S. Kazemi and M. A. Abdol
(i) their high permeance could enable higher energy efficiency and compact,
high-productive membrane separation systems [68, 85, 86].
(ii) their robustness due to high chemical resistance and mechanical strength
could prove useful for operation under harsh conditions, e.g., better withstand chlorine, allow more aggressive cleaning procedures [86], overcome
challenges of aging, compaction and influence of solvents in organic solvent
nanofiltration [7].
(iii) in case of providing universal size-based rejection independent of the solute,
it would benefit applications involving a diversity of solutes, e.g., removal
of persistent organic pollutants and boron from seawater or in chemical
processing [1, 3, 7, 14, 87].
(iv) their flatness could overcome fouling [20].
Built on what is explained so far, an ideal RO membrane based on nano-porous
atomically thin materials would be extremely flexible and mechanically stable to
fit into the spiral-wound RO modules for the highest efficiency. It would also be
extremely flat to mitigate fouling, and it would be decorated with pores of ideal
nano-sizes and distributions to break permeability–selectivity trade-off. Besides, it
would be extremely thin, to maintain high water permeation as shown schematically
in Fig. 2.
Another important aspect of the RO membrane is the substrate underneath the
active layer or the so-called ‘support layer’. The principal role of the substrate is
to provide mechanical support for the active layer via bearing most of the hydraulic
load and at the same time, distributing the pressure from the water onto patches of the
active layer. However, the substrate has a minor direct role in the salt rejection process,
while water simply percolates through its pore network after permeating through the
active layer [88–90]. In conventional TFC membranes, the active layer (typically
composed of polyamide) bears the salt rejection role and extends 100−200 nm in
thickness [91].
Fig. 2 Ideal RO membrane based on supreme characteristics of nano-porous atomically thin
materials