Mixed Matrix Membranes MMMs

This approach allows the exploitation of the inherently superior separation characteristics of inorganic particles, and at the same time, takes advantage of the processability of the polymer as the continuous matrix. Initial studies on this topic were related to the gas separation field, taking advantage of the flexibility of rubbery polymers [43] more recently, MMMs based on PDMS were also studied 

Fumed silica, consisting of spherical nonporous particles, is a cheap filler commonly used to reinforce silicone rubber [48, 49[. Different studies showed that it is 

The general procedure to fabricate dense MMM is as follows i) preparation of homogeneous polymer/inorganic filler/solvent mixture, ii) casting the solution on a smooth plate, iii) evaporation of the solvent, and sometimes iv) annealing the membrane at high temperatures to remove the residual solvent. 

The bulk phase (phase A) is typically a polymer the dispersed phase (phase B) represents the inorganic particles, which maybe zeolite, carbon molecular sieves, or nanosized particles. Thus, MMMs have the potential to achieve higher selectivity, permeability, or both, relative to the existing polymeric membranes, resulting from the addition of the inorganic particles with their superior inherent separation characteristics. 

Regarding the biomedical applications, MMMs seem to be used as membrane adsorber, where the filtration capacity of polymeric membrane and adsorption capacity of fillers are combined. 

For example, Ronco [48] suggested the possibility of mixing the biomaterial of a specific membrane with a sorbent material based on a significant enhancement of internal and backfiltration in hollow-fiber hemodialyzers. Thus, the single membrane will have both characteristics, i.e., diffusion and adsorption for removal of uremic acid, and is called mixed matrix membrane (MMM) [49,50]. The MMM concept had been proposed earlier as an alternative to traditional chromatographic column [51]. 

Tijink et al. [52] suggested that besides removal of protein-boimd toxins, the MMM might also be useful in liver failure or sepsis by combining renal support and targeted adsorption. The MMM might be useful for a wearable artificial kidney due to the incorporation of sorbents within a membrane. However, their development is still in an early stage. The MMMs prepared by phase inversion, using mixture polymer (cellulose acetate, polyethersulfone (PES)/polyvinylpyrrolidone (PVP) polymer blend) and activated carbon, were successfully applied for removal of creatinine. 

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Figure 11.2 Selection of proper zeolite material for a mixed-matrix membrane (MMM) using the Maxwell model.

Chung, T.S., Jiang, L.Y., li, Y., and Kulprathipanja, S. (2007) Mixed matrix membranes (MMMs) comprising organic polymers with dispersed inorganic fillers for gas separation. Prog. Polym. Sci., 32 (4), 483-507. 

An example is provided by mixed matrix membranes (MMM). Basically they are constituted of inorganic molecular nanoparticles (such as zeolites, carbon molecular sieves, etc.) imbedded in polymers. MMMs open up new perspectives in gas separation. A main application for sustainable development is the purification of... 

Figure 4.4 Mixed matrix membranes (MMM) with covalent linking of rigid entities like buckyballs into polymers.

To overcome these limitations, mixed matrix membranes (MMM) started to emerge as an alternative approach in membrane technology. In this approach, the superior gas separation properties of the molecular sieve materials combine with the desirable mechanical properties and economical processability of polymers (Moore et al. 2004). A mixed matrix is a blend of inorganic particles (such as nanoparticles) in a polymer matrix, which are well dispersed. The effect of the inorganic dispersed phase on the MMM properties is related to its chemical structure, surface chemistry, and the type of particles. The inorganic materials used... 

Mixed-matrix membranes (MMMs), also referred to as hybrid membranes, contain a separating layer made of a continuous phase (usually a polymer) embedding a second,... 

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). 

M. Rezakazemi, A. Ebadi Amooghin, M.M. Montazer-Rahmati, A.E Ismail, T. Matsuura, State-of-the-art membrane based CO2 separation using mixed matrix membranes (MMMs) an overview on current status and future directions. Progress in Polymer Science 39 (2014) 817-861. 

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