A Critical Review on Thin-Film Nanocomposite Membranes with Interlayered Structure: Mechanisms, Recent Developments, and Environmental Applications

Abstract

The separation properties of polyamide reverse osmosis and nanofiltration membranes, widely applied for desalination and water reuse, are constrained by the permeability-selectivity upper bound. Although thin-film nanocomposite (TFN) membranes incorporating nanomaterials exhibit enhanced water permeance, their rejection is only moderately improved or even impaired due to agglomeration of nanomaterials and formation of defects. A novel type of TFN membranes featuring an interlayer of nanomaterials (TFNi) has emerged in recent years. These novel TFNi membranes show extraordinary improvement in water flux (e.g., up to an order of magnitude enhancement) along with better selectivity. Such enhancements can be achieved by a wide selection of nanomaterials, ranging from nanoparticles, one-/two-dimensional materials, to interfacial coatings. The use of nanostructured interlayers not only improves the formation of polyamide rejection layers but also provides an optimized water transport path, which enables TFNi membranes to potentially overcome the longstanding trade-off between membrane permeability and selectivity. Furthermore, TFNi membranes can potentially enhance the removal of heavy metals and micropollutants, which is critical for many environmental applications. This review critically examines the recent developments of TFNi membranes and discusses the underlying mechanisms and design criteria. Their potential environmental applications are also highlighted.

Fabrication of desalination membranes by interfacial polymerization: history, current efforts, and future directions

“…Readers are referred to a comprehensive review for the recent progress in the use of sacrificial interlayers in IP. 24 In addition to the use of nanomaterial-tailored supports, another strategy is to perform IP at a free interface between an aqueous phase and an organic phase. 25,26 The liquid interface enables more rapid heat dissipation than that in an aqueous solution trapped in solid support, forming free-standing nanofilms with smooth surfaces due to inhibition of interfacial instability.…”

2D nanosheet enabled thin film nanocomposite membranes for freshwater production – a review

“…Despite enhanced permeance at 15 L m À2 h À1 bar À1 for the TFN membrane, the specific energy consumption predicted was reduced by a mere 16.6% when compared to commercial TFC membrane with 1 L m À2 h À1 bar À1 permeance. 44 From the marginal reduction in this case, it is evident that energy consumption is more dependent on the osmotic pressure of the feed and the operating conditions rather on permeance. It was observed that energy consumption reduces for operations such as BWRO and NF membranes operating at 5-10 bar pressure.…”

“…42,43 Last, 2D nanosheets may be applied onto the surface of the membranes to decorate the PA layer in a controlled manner. 44,45 The conventional IP reaction involves removal of the aqueous phase, utilizing rubber roller or airgun or air knife. Emerging innovations open up methods such as vacuum filtration, spin coating and electrospraying-assisted IP reaction techniques which facilitate the contact of the aqueous phase on the support membrane.…”

“…9,11,16,18 The increase in surface roughness is on account of the confinement effect of the gas bubbles produced during the IP reaction. 44 The IP reaction leads to formation of CO 2 bubbles which are released through the PA layer. The encapsulation of the nanosized gas bubbles into the PA layer caused due to the influence of nanosheets, leads to the formation of nanovoids and leaf-like structures along with the conventional ridge-valley protuberances in the PA layer.…”

Review of Thin Film Nanocomposite Membranes and Their Applications in Desalination

“…The TFN membranes provided improvement in chlorine resistance and antifouling properties (wang et al, 2011).Despite such unique properties, dispersion of hydrophilic nanoparticles and leaching of nanoparticles into retentate and permeate has raised the environmental concerns and need further research. As the world is facing shortage of freshwater, thin film nanocomposite (TFN) membranes are anticipated to accelerate desalination industry and it can be extended as selective membranes for CO 2 separation (Wong et al, 2016).The incorporation of functionalized fillers such as GO, CNT, TiO 2 , Ag-TiO 2 , MOFs (Figure 10) or organic fillers for specific applications has the potential to enhance membrane performance (Kumar et al, 2020).Recently, an interlayer of nanomaterials (TFNi) membranes showed extraordinary improvement in water flux and selectivity that can be used for the removal of heavy metals and micropollutants at a large scale (Yang et al, 2020).In the near future, high impact TFN membranes with antifouling and biofouling properties, chemical resistance, improved mechanical strength and thermal stability need to be produced by either predisposition of new types of functionalized nanofillers or organic fillers compatible with selective layers of respective membranes. Such design and development of TFN membranes may pave way for more robust membrane systems with increased performance and long term durability providing precise solutions for various commercial water treatment challenges.…”