Environmental Engineering Reference
In-Depth Information
Chunlong Kong et al. described an alternate approach to TFN membranes by using
titanium isopropoxide, bis(triethoxysilyl)ethane, or phenyltriethoxysilane as nanoparticle
precursors [22]. Phenyltriethoxysilane was found to give up to a doubling of the water
transport with a negligible change of rejection.
Hang Dong et al. explored the use of surface-modiied zeolite nanoparticles to improve
the compatibility of the hydrophilic nanoparticles in the hydrophobic solvent as a means
to decrease aggregation [23]. The resulting membranes were found to give less aggregation
and slightly improved rejections relative to non-surface modiied zeolite additives.
Lin Zhang et al. explored a surface modiication of a different nature; they modiied
hydrophobic carbon nanotubes with a mixture of sulfuric and nitric acids to make them
more hydrophilic and compatible with the aqueous solution [24]. The resulting membranes
appeared to have carbon nanotubes spanning the membrane layer, and had more than
double the permeability, but with a signiicant fall off in NaCl rejection.
A larger pore iller was described by Kim and Deng. They describe the preparation and
use of an ordered mesoporous carbon (OMC) iller prepared around a silica template and
later made hydrophilic by treatment with plasma [25]. Addition of this material resulted in
a TFN membrane with increased surface hydrophilicity and pure water permeability; fur-
thermore, bovine serum albumin adsorption was reduced with increasing amounts of OMC.
By changing the nature of the monomers to polyethyleneimine and isophthaloyl chlo-
ride, Sagar Roy et al. developed a carbon nanotube-containing TFN nanoiltration mem-
brane [26]. Tested for organic dye rejection both in water and in methanol, the resulting
membranes had nearly an order of magnitude higher permeability relative to previously
reported TFC membranes. An alternate nanoiltration formulation was described by Deng
Hu et al. when a piperazine trimesoyl chloride-based TFN membrane was prepared with
incorporated silica nanoparticles [27]. These TFN nanoiltration membranes had approxi-
mately 20% higher permeability than TFC controls.
An alternate nanoparticle zeolite species was used by Mahdi Fathizadeh et al. when
NaX was used in the fabrication process [28]. Resulting membranes had nearly twice the
lux with similar salt rejections to TFC controls.
Although discussion of membranes using nanocomposite supports alone is outside the
scope of this discussion, an article by Mary Pendergast et al. describes a set of membranes
comprising a designed experiment looking at the effect nanocomposite supports (nTFC)
and nanocomposite thin ilms (TFN), and combinations of both (nTFN) [29]. This nTFN
approach was continued in a article by Eun-Sik Kim et al. using carbon nanotubes in the
support, and silver nanoparticles in the thin ilm [30]. The prepared membranes showed
greater resistance to
Pseudomonas aeruginosa
deposition and increased permeability. In a
later article, Eun-Sik Kim et al. used carbon nanotubes both in the thin ilm layer for use
in processing of tar sands produced water [31]. TFN membranes incorporating acid-treated
multiwalled carbon nanotubes had better rejection of hydrophobic organic pollutants,
higher process lux, and signiicantly reduced fouling.
Improved permeability and hydrophilicity was also observed by addition of alumina
nanoparticles in work by Saleh and Gupta [32].
Ning Ma et al. extended the applicability of TFN membranes by exploring the perfor-
mance of NaY zeolite containing TFN membranes to forward osmosis testing [33]. TFN
membranes gave 80% higher permeability than baseline membranes.
Both porous and nonporous MCM-41 nanoparticles were incorporated into TFN mem-
branes by Jun Yin et al. [34] TFN membranes were found to be more hydrophilic, more
rough, more negatively charged, and with porous MCM-41 (“Mobil Composition of
Matter”), of higher permeability.
