Composite Membrane

modify transport properties of RO membranes by employing different types of molecular sieve nanoparticles in PA fi lm [48,49]. Fig. 5 depicts the new concept of embedding molecular sieve nanoparticles in the top selective layer in the preparation of thin fi lm nanocomposite (TFN) membrane. The new concept was fi rst started by Hoek et al. [48] in early 2007. In their pioneering work, it is experienced that the super-hydrophilic and negatively charged zeolite-A embedded throughout PA thin fi lm was able to dramatically improve the permeability of the TFN membrane and remained equivalent salt rejection when compared with the pure PA composite membrane. Since the size of the zeolite particles is designed to match the PA fi lm thickness, it thus provides a favorable fl ow path through each particle incorporated into membrane, leading to high water permeation [49]. This improved membrane water process is just as effective as current technology but more energy ef fi cient and potentially less expensive. In order to further enhance water molecules transport rate, Fathizadeh et al. [50] in year 2011 impregnated bigger pore size of zeolite NaX (7.4 Å) in the thin fi lm layer with the aims of creating larger molecular tunnels for water to fl ow. It is found that this particular pore size of zeolite offers preferential fl ow paths for water molecules of 2.7 Å in diameter but restricts the permeation of hydrated sodium and chloride ions (8 – 9 Å). Instead of differences in particles' size, controllable design in interfacial chemistry of mem- brane is also possible using other type of molecular sieves, owing to their tunable functionality with respect to hydrophilicity, charge density and antimicrobial capability. It was recently reported by Kim and Deng [51] that hydrophilized ordered mesoporous carbons (H-OMCs) modi fi ed from pristine OMCs were possible to be used as nano- fi ller in making thin- fi lm polymer matrix of improved proper- ties. According to them, the plasma treated H-OCMs could be well dispersed in the aqueous solution which were likely to minimize large

high contact angle of 141.0° is observed for this composite fiber which shows the higher hydrophobic nature of the membrane. The prepared polymer composite membrane was soaked in the electrolyte solution and used as polymer electrolyte. Employing the polymer electrolyte, DSSCs were fabricated successfully and their photovoltaic performances were evaluated. The solar-to-light electricity conversion efficiency of the quasi-solid-state solar cells with the electrospun PVdF-PAN-V 2 O 5

Curing temperature has a great influence on TFC membrane performance. Low curing temperatures resulted in unstable thin barrier layer lamination, while too high temperatures damaged the polyesteramide barrier layer and undesired physical change occurred on the thin composite membrane. Cellulose acetate is not a suitable porous support for thin composite membrane. The asymmetric cellulose acetate membrane containing an additive such as acetone produced closed pore and dense membrane structure that contributed to the very low flux rate. Laminating an active layer on top of the membrane surface made the skin layer thicker and increased the membrane resistance. It is suitable to add non-solvent additive such methanol [20] to the cellulose acetate polymer formulation rather than applying an active layer on top of the membrane surface to increase the flux performance of cellulose acetate. Polysulfone membrane is a very suitable porous support for thin composite membranes. The results showed that the value of the water permeability constant (A) and solute transport parameter (D AM /k δ) influenced the membrane surface

In conclusion, a low methanol crossover and high water uptake composite membrane was developed by simply repeated coating. The SGO/Nafion composite membrane provided lower methanol permeability for its unique selectivity between methanol and water molecules. On the other hand, the SAC/Nafion composite membrane offered a better water retention due to the porosity and surface area of the activated carbon. The bilayer composite membrane had lower methanol permeability than Nafion 212 while maintaining higher water uptake. The power density of passive DMFC made of the bilayer composite membrane was 10% better than Nafion 212 and lasted for 24h. With this method, composite membranes with multi-functions can be easily designed by control casting solvent and the gap of the wet film.

Under the same concentration (10 mg L -1 ) condition, the antioxidant capacity of ascorbic acid, caffeic acid, coumaric acid and resveratrol was investigated respectively (Figure 5 inset). The AOT % of ascorbic acid, resveratrol, coumaric acid and caffeic acid were calculated as 73.5%, 71.6%, 64.4% and 60.7%, respectively. The results showed that different antioxidants have different antioxidant capacity. The highest values was obtained for ascorbic acid and followed by resveratrol. Caffeic acid has the lowest antioxidant capacity. The conclusions are consistent with the reference of [30]. Compared with the other electrochemical biosensors [27, 28, 31], the guanine damage processes and the protection of antioxidants for it in this biosensor were not conducted directly in Fenton solutions, but via a series of biochemical reactions in a composite membrane. These processes are more similar with those processes in vivo. The proposed biosensor had potential use in determination of the total antioxidant capacities in fruit juices.

A novel composite membrane of silver doped poly aminosulfonic acid was fabricated by cyclic voltammetry. This membrane had excellent properties for catalyzing the redox of NE. Compared with the membrane of poly aminosulfonic acid without silver, the peak currents of NE had significant increase and the ascorbic acid had no influence for the determination of NE. The proposed method had broad linear range, high sensitivity and good selectivity. It was used to determine the content of NE in injections with satisfied results. The recovery test showed that the recoveries varied from 97.3% to 102.1%.

Various physical and chemical properties of the PE, PMIA@PE and TP-PMIA@PE membranes are summarized in Table 1. The thicknesses of the two kinds of composite membranes are 20 μm and 24 μm respectively, thicker than pristine PE membrane (12 μm). However, the thickness of the composite membrane is suitable for separator of LIBs in portable electronic devices and electric vehicle applications [30]. The porosity of a separator is a crucial factor for electrochemical properties of LIBs. As shown in Table 1, the porosities of the PMIA@PE (58%) and TP-PMIA@PE membranes (67%) are higher than pristine PE membrane (40%), owing to the interconnected porous structure formed by non- solvent induced phase inversion process [31]. The addition of TP nanospheres affects the formation of pore structure to some extent. The TP-PMIA@PE composite membrane with high porosity possibly exhibits high liquid electrolyte uptake, further leading to a high ionic conductivity, which is consistent with the paper in Cao [32].

A time-dependent 2D axisymmetric model was developed for a hollow fiber composite membrane which is composed of poly (styrene-b-butadiene- b-styrene), triblock copolymer (SBS) with a rubbery character that is coated on a polyacrylonitrile (PAN) porous support [27]. A bundle of the membrane fibers modulated in a dead end membrane holder. According to the experimental paper, in this study, in spite of the common multilayer membranes, SBS selective layer was coated on the external surface of the PAN support, and because of the porous PAN support is used only for mechanical stability, it has no important role in species transport, or in turn, in the mass transfer mechanism and the separation performance. As well as in a constant height for a fiber, its radius and consequently the membrane surface area increases. Therefore, the amounts of species transport across the membrane or the mass flow rate increase that has no considerable effects on the permeability and selectivity.

to the great hydrophilicity of PMAPS. All the membranes have long-finger like structure and highly porous middle which eases the water transportation across the membrane. The higher the loading of PMAPS, the rougher the membrane surface. Apart from that, the zwitterionic properties of PMAPS helps to increase the membrane’s hydrophilicity and resulted in higher water flux of 15.12 LMH compared to neat membrane of 12.54 LMH using 2M NaCl as draw solution. At the same time, it is also able to provide very decent oil rejection up to 99.9% and oil flux of <0.01 gMH. Under RO mode, the pure water permeability coefficient and salt permeability coefficient of PMAPS- TFC membrane are also decent which are 0.69 and 0.56 LMH, respectively. However, excessive loading of PMAPS can cause non-uniform pores of different sizes distributed randomly throughout the membrane structure resulting in distorted membrane structure and properties thus poor performance. Characterizations from FESEM and AFM further prove the validity of this

Polymer membranes are extensively used for water treatment but they wear irreversibly over time, especially when used in treatment of waters containing abrasive substances such as in seawater pretreatment. Novel nanocomposite membranes may be a cost effective approach to improving membrane physical endurance. Various methods of dispersing commercially available Cloisite ® 30B nanoparticles in 1-methyl-2-pyrrolidinone (NMP) were investigated and the respective particle sizes were measured by nanoparticle sizer. Ultrasonication dispersed the nanoparticles to the smallest size in the shortest period of time. Flat sheet poly(vinylidene fluoride) (PVDF)/nanoclay membranes with 6.25 wt % clay loading were cast by phase inversion. The morphology and the structure of the membrane were characterized by scanning electron microscopy (SEM), combustion testing and thermogravimetric analysis (TGA). Porous membrane with fingerlike macrovoids was fabricated and 1.7 wt% of nanoclay was incorporated into the final product as shown by TGA. The composite membrane showed greater stiffness compared to pure PVDF membrane.

membranes show enhanced thermal stability and the composite membrane shows first major weight loss centred around 180 o C. This corresponds to weight loss of absorbed water, structural water associated with STA and water as by-product by further esterification in the PVACO/STA membranes. The second weight loss is centred around 250-450 o C is due to the thermal degradation of the ether and ester crosslinking linkages. The third weight loss is due to degradation of the polymer backbone and/or reaction with air, which starts at around 600 o C. The crosslinked PVACO/STA composite membranes showed considerably enhanced thermal stability than that of the pristine PVACO membranes. Recently it has been demonstrated that silicotungstic acid and PVA composite membranes prepared via sol-gel technique offer good thermally stability at high temperature [25].

This work reports the fabrication and characterization of PVACO-PTA based crosslinked composites by various characterization techniques. The FTIR studies confirmed the formation of crosslinked networks and the occurrence of strong interaction of the heteropoly acids with the hydroxyl and carboxylic acid groups of the PVACO polymer matrix through the terminal and bridging oxygen atoms, which helps in immobilizing the PTA in the PVACO polymer matrix. The water uptake and the dopant loss from the composite membranes can be controlled by optimizing the PTA content and the crosslink density of the composite membranes. The optimum membrane property among the PVACO-PTA composites was observed for the membrane with 50 wt. % PTA and 0.5 ml GA CLR, a conductivity of 2.3 x 10 -3 S/cm and a methanol permeability of 3.35 × 10 -6 cm 2 /s was observed for this PEM. The variation in conductivity with temperature follows an Arrhenius relationship and the values of activation energy for proton conduction in the PVACO-PTA composite membranes ranges between 0.13 -0.17 eV as determined from the Arrhenius plots. Improvement in thermal and mechanical properties of the PVACO-PTA composites was observed with the incorporation of PTA in the PVACO polymer matrix and crosslinking of the polymer matrix respectively. X-Ray diffraction studies showed decrease in crystallinity of the composite membranes which plays an important role in enhancing the proton conductivity of the composite membranes. All the PVACO-PTA composite membranes showed very smooth surface morphology as observed by the AFM except for the composite membrane with the highest (50 wt %) acid content.

In the discussions of IFC membranes that follow, technical milestones are highlighted with emphasis on commercially signi R cant developments. The early period of membrane development shown in Table 2 began in 1967 with the investigation of various aque- ous diamine and hexane } diacyl chloride interfacial solutions upon polysulfone porous supports by Rozelle et al. at North Star Research Institute. These R rst IFC membranes had low salt rejections, probably due to lack of R lm integrity since the resultant poly- mers were not cross-linked. This pioneering work, however, is signi R cant in that the essential elements for the preparation of IFC membranes were demon- strated. Shortly thereafter, in 1970, the R rst high salt-rejecting IFC membrane, NS-100, was also de- veloped at North Star Research. This membrane was made from polyethylenimine (PEI) in the aqueous solution and toluene diisocyanate (TDI) in the hexane solution. The coated and drained polysulfone support was subsequently dried at 110 3 C to yield a dry composite membrane with greater than 99% salt rejection on a synthetic seawater feed at 1000 psig (6.9 MPa). A later related membrane, des- ignated NS-101, substituted isophthaloyl chloride (IPC) for TDI as the cross-linker and provided similar results. The selective layers in these membranes con- sisted of cross-linked polyurea and polyamide R lms, respectively. The membranes demonstrated high perm- selectivity but were mechanically delicate and highly vulnerable to attack by chlorine disinfectant.

agent, i.e. 1-4-diamino benzene (DABZ), to produce the functional groups on the CNTs surface. The Fourier transform infrared (FTIR) spectra indicated the presence of carboxylic- and amine-functional groups on the nanotubes surface. Asymmetric PSF composite membrane with various levels of the functionalized CNTs were prepared to investigate the effect of functional group type on the morphology and water flux rate of the resulting membranes. The results showed that the incorporation of the functionalized CNTs up to 0.5 wt% increased the pore size and surface roughness of the sheet membranes, while further addition decreased porosity and roughness. Higher water flux rate was observed for the amine-functionalized CNTs (af- CNTs) reinforced PSF membrane when compared with the membranes reinforced with the carboxyl-functionalized CNTs (cf-CNTs). The stronger compatibility between af-CNTs and the PSF matrix caused higher water permeability. The salt rejection performance of these microfiltration composite membranes was evaluated.

By increasing PES concentration, the size and number of pores decreased and the sponge-like area spread which affect the water permeation through the membrane. By adding 2.25 wt% PVP to dope, pores became larger and water flux increased. Substrate membrane with 15% PES and 2.25% PVP had appropriate morphology and water flux and was chosen for composite membrane. CS/ PES composite membrane had 76.58% retention of copper ions. The MWCO of the resultant membrane was 1048.5 Da (in the NF range) and mean pore size was about 0.99. These results indicated that the Chitosan/polyethersulfone (CS/PES) composite membrane is a very promising membrane materials used for the removal of metal ion from industrial wastewater.

Chapter 3 deals with the materials and methods used to investigate the appropriate parameters, experimental set-up, test conditions, characterization using analytical equipment and material evaluation involved in the fabrication and evaluation of the composite membranes. The synthesis of NAp powder is reported in the first part of the chapter. Subsequently, the development of PLGA based NAp-LA composite membrane through a new fabrication technique using solvent casting- TIPS-solvent leaching is reported. This is followed by the development of methods to test on the membrane’s properties such as physico-chemical, mechanical, in vitro degradation profile over six months duration, quantification of LA release and finally, LA release mechanism; since the effects of NAp and LA additions in the PLGA membranes are highly imperative to meet the design criteria of membranes for GBR applications.

The growing awareness on environmental issues and energy crisis due to depletion of fossil fuels pressing researchers in finding alternative source of energy with almost zero emissions. The development of polymer electrolyte membrane (PEM) with higher ionic conductivity is the main objective in recent research. PEM have been studied for their application in batteries, fuel cells and sensors. Fuel cells are excellent electrochemical energy conversion devices that directly convert the chemical energy of the fuel into electric energy with almost zero emission of unwanted gas 1 . Proton exchange membrane is the most vital part of a fuel cell as it separates the fuel from oxidant and conducts electrons to external load. Among the sulfonated aromatic polymers (SAP), Polyimide (PI) is the most promising proton exchange membrane (PEM) for fuel cell application 2,3 . PI has outstanding chemical, mechanical and thermal resistance properties. Incorporation of the polyimide (PI) with α-cyclodextrin (α-CD) introduces hydrophilic properties to this Polymer electrolyte

PI (Otto Chemie), α-cyclodextrin (α-CD) (Alfa Aesar) were the chemicals (AR grade) used in this study. The PI/ α-CD polymer electrolyte membranes were prepared by solution casting technique. The solvent, m-Cresol (>99%), was supplied by Merck. An appropriate amount of PI was dissolved in m-Cresol solvent at a constant rate of stirring (500 rpm) at 100 °C for 6 hours and α-CD were dissolved separately in m-Cresol and the solutions were mixed together and casted in Petri dish then dried to form a blend membrane.

The SEM images are shown in Figure 1. SEM observation show many round and oval holes on the membrane surface (see Figure 1), and that the tridimensional porous structure with macropores can be observed in the cross-section of the membrane (see Figure 1). The membrane appeared in a high extended state, and the two components were mixed homogeneously without obvious aggregation. This spongy structure was favorable for moisture permeability, carbon source nutrients releasing and bacterium growing. Meanwhile, the membrane surface became rougher, which was propitious to microbial immobilization.

Despite NF0 possess highest permeate flux, the repulsion of water molecules away from hydrophobic PVDF nanofibers membrane surface is an impulsive process with an entropy increasing and therefore the tendency of unwanted particles to absorb onto the membrane surface and dominate the boundary layer. Thus, this may lead to different membrane stability. NF0, NF1, NF2, NF3 reach stability at different time period (100, 150, 180, and 150 min, respectively). Nanofibers membrane is a matrix of multiple nano sheets layers were each layer have complex inter- connected fibers. Within this interconnected fibers, the cavity opening/pore were formed due to the nature of electrospinning. Structural analysis from the morphological of the electrospun nanofibers, NF1 and NF3 shows the formation of beaded fibers due to AC loading cause a greater cavity/pore from the interconnected fiber floss cause the cavity/pore are larger compared the electrospun nanofibers that does not have beaded fiber. This influences the water permeability performance of the nanofibers membrane. NF1 and NF3 nanofibers membrane fluxes rate are relatively high when compared to NF2 nanofibers membrane. The flux value for NF1 and NF3 are 467.27 L/m2h and 510.78 L/m2h respectively.