Page 472 - Polymer-based Nanocomposites for Energy and Environmental Applications

Nanocomposite membrane for environmental remediation 425

N 2 , and CH 4 , remarkable improvement has been made on the development of nano-
structured membranes.
Zhao et al. [143] for high-pressure CO 2 /H 2 separation used both untreated
multiwalled carbon nanotubes (MWNTs, 10–15 nm in diameter and 0.1–10 mm in
length) and acid-treated multiwalled carbon nanotubes (AT-MWNTs) as mechanical
reinforcing fillers in the cross-linked poly(vinyl alcohol)-poly(siloxane) membrane
matrix. No change was found in the membrane performance using a CO 2 permeability
of 836 Barrers and CO 2 /H 2 selectivity of 43 during the first 18.5 days test at 1.52 MPa
and 380.15 K, respectively. The improvement was ascribed to the ability of MWNTs
to improve the mechanical strength and anticompaction property of the mixed matrix
membranes. The optimum untreated MWNT loading was 2 wt%, and as the MWNTs
increased further, the membrane performance was reduced with time because of the
poor dispersion of the MWNTs. However, the dispersion improved with AT-MWNTs.
The membrane with 4 wt% of AT-MWNTs had a stable membrane performance with
aCO 2 permeability of 896 Barrers and a CO 2 /H 2 selectivity of 50.9 for at least
11 days.
Similarly, Shen et al. [145] reported a CO 2 permeability of 100 Barrers and a
CO 2 /N 2 selectivity of 91 by simply incorporating laminar structures of graphene oxide
into the polyether block amide (PEBA) matrix using a thickness of 6–15 nm.
Buonomenna [146] studied inorganic zeolite membranes including silicalite,
ZSM-5, sodalite (SOD), and Linde type-A (LTA) zeolites.
Kim et al. [147] produced poly(arylene ether sulfone) comprising functional
zeolite nanoparticles and obtained a water flux of 22.3 gfd and a salt rejection
of 98.8%.
Nanostructured membranes have been widely used for ultrafiltration. Ultrafiltra-
tion is a membrane-based separation method employed in a variety of applications
such as water treatment and product separation in food, dairy, textile, and chemical
industries. Ultrafiltration membranes normally have pores in the nanoscale range
of 1–100 nm and are formed by the phase inversion method [148].
One of the new advances in the research of ultrafiltration membranes is the incor-
poration of inorganic nanoparticles in order to enhance the membrane properties such
as mechanical strength, structure, hydrophilicity, and surface charge [149,150].
PSf is frequently designated due to its availability commercially, fluid transport
properties, ease of handling, and thermal stability [151].
Wu et al. [152] merged silica-graphene oxide (SiO 2 -GO) nanohybrid into a PSf
membrane and improved the water flux up to two times of the PSf membrane.
Similarly, Alhoshan et al. [153] discovered that nano-ZnO-based PSf membrane
had a hydrophilic, smooth, tightly packed surface and a spongy structure with
well-interconnected pores.
For water treatment application, poly(vinylidene fluoride) (PVDF) is the most
common polymer employed in low-pressure ultrafiltration. PES is extensively
employed due to its outstanding properties like oxidative, thermal strengths, and
mechanical property [154].
To synthesize ultrafiltration membranes, other polymers (polyacrylonitrile, polyi-
mides, polyamides, and polytetrafluoroethylene) can also be used, respectively.