Dual-layer membranes

Inter-layer Diffusion in Dual-Layer Membranes... 

Figure 31.12 displays the desirable skin morphologies at various locations of dual-layer membranes. Briefly, both the inner and outer skins of the inner layer are porous with intimate adhesion between them. When using two different materials, one can control the interlayer diffusion as a function of spinning conditions. Table 31.2 summarizes the elemental analysis data of the interfacial layers of hollow fibers spun from PES as the inner layer and Matrimid polyimide as the outer layer at different spinneret temperatures (Jiang et al., 2004). After being extruded from the spinneret, the two dopes should make contact with each other under normal conditions. When the spinneret temperature is low (i.e., 25°C), their viscosities are high, the diffusion rate of the polymer molecules between the two layers will not be fast therefore, no sulfur can be found in the outer layer, as shown in this table. When the spinneret temperature is increased to 60°C, the interlayer diffusion between the two polymers apparently occurs, as evidenced in Table 31.2, in which it is... 

Fabrication of dual-layer membranes either in hollow-fiber or flat-sheet configuration is rather complex as many parameters are involved, which control the thermodynamic property and the phase inversion kinetics to obtain good lamination between the two layers as well as regular and uniform membrane cross-sectional morphology. Fabrication parameters can be classified into the chemistry of polymer solutions and the operating conditions. The chemistry of polymer solutions depends on the polymer concentration and type, the solvents affinity to the polymer or coagulant, and... 

D. A. Nivens, M.V. Schiza and S.M. Angel, Multilayer sol-gel membranes for optical sensing applications single layer pH and dual layer C02 and NH3 sensors, Talanta, 58(3) (2002) 543-550. 

Thin-film composite mixed-matrix membranes can be made by a coating method or by a dual-layer co-extrusion technology, as discussed in Section 11.5.2.2. 

Dual-layer polyethersulfone (PES)/BTDA-TD1/MD1 co-polyimide (P84) hollow fiber membranes with a submicron PES-zeolite beta mixed matrix dense-selective layer for... 

J. Brinker, C.-Y. Tsai and Y. Lu, Inorganic Dual-Layer Microporous Supported Membranes, US Patent 6,536,604 (March 2003). 

Husain, S. (2006). Mixed Matrix Dual Layer Hollow Fiber Membranes for Natural Gas Separation, in Chemical Biomolecular Engineering, PhD Dissertation, Georgia Institute of Technology. 

Tsai CY, Tam SY, Lu YF, and Brinker CJ. Dual-layer asymmetric microporous silica membranes. J. Membr. Sci. 2000 169 255-268. 

Fig. 10.1. Different membrane concepts incorporating an oxygen ion conductor (a) mixed conducting oxide, (b) solid electrolyte cell (oxygen pump), and (c) dual-phase membrane. Also shown is the schematics of an asymmetric porous membrane (d), consisting of a support, an intermediate and a barrier layer having a graded porosity across the membrane.

Liu, Y. Chung, T.S. Wang, R. Liu, D.F. Chng, M.L. Chemical cross-linking modification of polyimide/poly(ethersulfone) dual layer hollow fiber membranes for gas separation. Industrial Engineering Chemistry Research 2003, 42 (6), 1190-1195. 

PI materials have been used for the dehydration of water/alcohol mixtures by the pervaporation method.P84 co-PI hollow fibers and zeolite filled P84 CO-PI membranes " have been used for the pervaporation dehydration of isopropanol. In addition, P84 co-PI based dual-layer hollow fiber membranes serve for the dehydration of tetrafluoropropanol. ... 

K. Y. Wang, T.-S. Chung, and R. Rajagopalan. Dehydration of tetrafluoro-propanol (TFP) by pervaporation via novel PBI/BTDA-TDI/MDI co-poly-imide (P84) dual-layer hollow fiber membranes. J. Membr. Sci., 287(1) 60-66, January 2007. 

Dual-layer mixed matrix membrane adsorbers consisting of a particle-free membrane layer and a mixed matrix layer containing activated carbon were recently investigated for blood purification [164]. The particle-free membrane layer (on the blood-contacting side. Figure 6.14) showed an improved hemocompatibility while preventing particle release from the adsorber. The membranes efficiently combine diffusion and adsorption of uremic retention solutes in one step. 

FIGURE 6.14 Dual-layer mixed matrix membrane adsorber. 

Copoly (4,4 -diphenyleneoxide/l, 5-napthalene-2,2-bis (3,4-dicarboxyl phenyl) hexa fluoro propane diimide) 6FDA-ODA-NDA/Ultem 1010 dual-layer hoHow-fiber membrane... 

P. Wang, M.M. Teoh, T.-S. Chung, Morphological architecture of dual-layer hollow fiber for membrane distillation with higher desalination performance. Water Research 2011, 45, 5489-5500. 

C. Tsai, S. Tam, Y. Lu, C. J. Brinker, Dual layer asymmetric microporous silica membranes. Journal of Membrane Science 169 (2000) 255. 

Moreover, to decrease the material cost for CMS membrane will also be an important factor in future research. A dual-layer CMS membrane, which uses the polyimide and cheaper materials (z.e. PSf, CA) as the inner and outer layers respectively, could be an opportunity to decrease the membrane cost while ensuring high membrane performance. 

Dual layer hollow fiber membranes have become increasingly attractive due to which they can be fabricated in a single step using the non-solvent induced phase inversion method. A good lamination between the two layers as well as a regular morphology are critical to get a functional hollow fiber membrane [80]. 

Setiawan L, Shi L, Krantz WB, Wang R. Explorations of delamination and irregular structure in poly(amide-iniide)-polyethersulfone dual layer hollow fiber membranes. J Membr Sci 2012 423 24 73-84. 

Setiawan L, Wang R, Tan S, Shi L, Fane AG. Fabrication of poly(amide-imide)-poly-ethersulfone dual layer hollow fiber membranes applied in forward osmosis by combined polyelectrolyte cross-Unking and depositions. Desalination 2013 312 99-106. 

Li, Y., Cao, C., Chung, T-S. and Pramoda, K.P. 2004. Fabrication of dual-layer polyether-sulfone (PES) hollow fiber membranes with an ultrathin dense-selective layer for gas separation. 245 53-60. 

Data from Ref. V. Nafisi, M.-B. Hagg, Development of dual layer of Z1F-8/PEBAX-2533 mixed matrix membrane for CO2 capture. Journal of Membrane Science 459 (2014) 244—255. 

In some of the cases listed in Table 3.1 catalytic membranes are used. For instance the catalytic membranes prepared by Peters et al. (2007) have a catalyst layer deposited on a composite hydrophilic membrane. The dual-layer structure allows the independent optimization of the selective and the catalytic properties and partially satisfies contradicting material properties , such as the necessity to achieve a low permeability of the reactants together with a high availability of the same reactants on the catalyst. The value of 5 can be varied by changing the number of dip-coat... 

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