Environmental Engineering Reference
In-Depth Information
16.2 Academic TFN Membrane Research
Owing to the incompatibility of methods used to prepare early mixed-matrix membranes
and the TFC membranes, it would be >25 years from early commercialization of TFC RO
membranes and the development of mixed-matrix membrane technology until the irst
reported mention of a combination of these membrane methods [4]. In February of 2007
(patent priority dates suggest this work was originally conducted ~2 years earlier [11]),
Byeong-Heon Jeong and Eric Hoek published results regarding TFC membranes incorpo-
rating nanoparticles in the active layer. These TFN membranes were prepared by dispers-
ing zeolite nanoparticles in the organic solvent phase of the interfacial polymerization
process. The structural differences between a TFC and TFN are illustrated in Figure 16.1.
Transmission electron microscopy (TEM) was conducted on cross sections of these
membranes to verify that the nanoparticles were incorporated within the polyamide layer,
and an example of these images shown in Figure 16.2.
TFN membranes prepared with increasing amounts of nanoparticles were found to have
increasing permeability with similar rejection to NaCl, MgSO
4
, and polyethylene glycol.
In addition to increased permeability, membranes prepared with the zeolite particles
were found to have higher hydrophilicity, a more negative surface charge, and a lower sur-
face roughness. These characteristics suggested a potentially improved structure to resist
foulant deposition.
Later, in April of 2007, Seung Yun Lee et al. reported on the incorporation of silver
nanoparticles by a similar method [12]. These silver-containing TFN membranes were
(a)
Polyamide
Polysulfone
(b)
Nanoparticle
FIGURE 16.1
Schematic of (a) TFC and (b) TFN membranes.
