Nanocomposite Mixed Matrix Membranes

CS-based mixed matrix membranes and nanocomposite membranes are much useful in heavy metal removal. Salehi et al. [82] synthesized amine functionalized multiwalled carbon nanotubes (F-MWCNTs) and utilized to prepare novel CS/polyvinyl alcohol (PVA) thin adsorptive membranes for copper ion removal from water. Copper ion adsorption on the membranes was more favorable at higher CNT contents as well as increased temperatures. The adsorption capacity of the membrane containing 2 wt.% CNTs (20.1 mg/g at 40°C) was almost twice as large as that of the plain membrane (11.1 mg/g). Salehi et al. [83] used PE glycol and amino-modified MWCNTs to modify CS/PVA thin adsorptive membranes for copper ion adsorption. Adsorption capacity of CS/PVA membrane was increased from 11 to 30 mg/g by the addition of 5 wt.% PEG to the blend. Addition of CNTs,... 

Nanocomposite membranes, also known as mixed matrix membranes, and FTMs are two distinguished and promising generations of gas separation membranes. 

Commercial membranes for CO2 removal are polymer based, and the materials of choice are cellulose acetate, polyimides, polyamides, polysulfone, polycarbonates, and polyeth-erimide [12]. The most tested and used material is cellulose acetate, although polyimide has also some potential in certain CO2 removal applications. The properties of polyimides and other polymers can be modified to enhance the performance of the membrane. For instance, polyimide membranes were initially used for hydrogen recovery, but they were then modified for CO2 removal [13]. Cellulose acetate membranes were initially developed for reverse osmosis [14], and now they are the most popular CO2 removal membrane. To overcome state-of-the-art membranes for CO2 separation, new polymers, copolymers, block copolymers, blends and nanocomposites (mixed matrix membranes) have been developed [15-22]. However, many of them have failed during application because of different reasons (expensive materials, weak mechanical and chemical stability, etc.). 

An important event of recent years in membrane science was the discovery of a new phenomena observed when nano-particles are added into (mainly high permeability) polymer matrix references to these pioneer works can be found in chapters of Section II Nanocomposite (Mixed Matrix) Membranes. So it is not surprising that several presentations at ICOM2008 dealt with such systems. Golename et al. (Chapter 6) investigated the Systran that contained perfiuorinated polymers and surface-fiuorinated zeolites as nano-additives. Perfiuorinated polymer AF2400 with nano-additives was also the object... 

Depending on the nature of the particles embedded in the polymeric matrix, polymer-inorganic hybrid membranes can be divided into two nonexclusive groups mixed matrix membranes (MMMs) and nanocomposite membranes (NCMs). 

V. Vatanpour, S.S. Madaeni, A.R. Khataee, E. Salehi, S. Zinadini, H.A. Monfared, Ti02 embedded mixed matrix PES nanocomposite membranes influence of different sizes and types of nanoparticles on antifouling and performance. Desalination 292 (2012) 19-29. 

Hanid NA, Wahit MU, Guo Q, Mahmoodian S, Soheilmoghaddam M (2014) Development of regenerated cellulose/halloysites nanocomposites via ionic liquids. Carbohydr Polym 99 91-97 Hashemifard SA, Ismail AF, Matsuura T (2011) Mixed matrix membrane incorporated with large pore size halloysite nanotubes (HNT) as filler for gas separation experimental. J Colloid Interf... 

Nanocomposite mixed-matrix membranes have been investigated for close to a decade. Ti02-poly(amide-imide) membranes showed selectivity improvement but suffered loss of productivity when TiOa was added. Nonporous, nanoscale, fumed silica was embedded in a glassy, amorphous polymer, poly(4-methyl-2-pentyne), which resulted in enhancements in both permeability and selectivity for the mixed-matrix membrane. These membranes were discovered to be reverse selective, so the membrane is selective for the larger penetrant. This phenomenon is attributed to increased free volume in the bulk polymer from chain packing disruption, which occurs when the filler is added. ... 

A widely investigated strategy for improving the properties of polymeric materials, overcoming the trade-off between permeability and selectivity observed in gas separation [42], consists of the addition of inorganic nanofillers, in order to get synergistic properties. Such hybrid or nanocomposite membranes are referred to as mixed matrix membranes (MMMs) and they are schematically represented in Figure 20.3. 

Similar efforts have been made in other application areas. In gas separation, the addition of Ti02 nanoparticles to polyvinyl acetate improved the thermal stability of the resulting membranes, which was demonstrated by an inaease in the glass transition temperature (Ahmad and Hagg 2013). In this case, it was found that the addition of Ti02 up to 10 wt% improved both the permeability and selectivity of the membranes for gas separation, including H2, CO2,02, and N2. Similar observations were made on the effect of silica nanoparticles on the permeability of CO2 and CH4 for two types of nanocomposite membranes based on polyester urethane and polyether urethane (Hassanajili et al. 2013). Khan et al. (2013) studied mixed matrix membranes composed... 

Nanoparticles have a proven potential as constituents in membrane synthesis to improve the membrane performance. Several methods have been applied to produce mixed matrix membranes with nanoparticles with variable success. Part of the uncertainties might be related to the unknown thermodynamics of the systems for some methods, in particular the bulk addition method. The self-assembly method may be insufficiently stable in longterm operation, but this can be improved using the layer-by-layer approach. A promising alternative is the approach in which nanoparticles are anchored on the membrane surface, as found in thin-film nanocomposites or by adhering nanoparticles using polydopamine. 

FIGURE 14.2 Illustration of in situ synthesis process of mixed-matrix nanocomposite membranes (a) metal ions are preloaded within polymer matrix to serve as nanoparticle precursor (b) monomers of polymer matrix and the nanofillers as the starting materials and (c) blending of the nanoparticle precursors and monomers of polymers in solvent. 

Nicotera et al. investigated the behavior of water confined in recast NAFION and in NAFION-clay hybrids membranes using PFGSE NMR and spin—lattice relaxation time Tj, and concluded that the transport mechanism is influenced from the dimensions of the dispersed platelets and mainly from the type of nanocomposites formed upon mixing the clay particles with the polymer matrix. Compared to pure NAFION, the water uptake and the water diffusion of the hybrid membranes are increased, with the exception of the Kunipia-NAFION composite [83]. 

---