• Membrane Journal
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• v.12 no.1
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• pp.28-40
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• 2002

The primary objective of this study is to elucidate the contribution of the electrostatic and molecula structural properties of an active layer of the thin film compsite (TFC) membranes to fouling tendency. The studies of surface morphology and surface charge were very effective in understanding fouling behaviors of the reverse osmosis (RO) membranes which were the thin film composite type of ployamide. Results of microscopic morphology analyzed by atomic force microscopy (AFM) and surface charge analyzed by electrokinetic analyzer (EKA) showed important factors affecting the fouling of RO membranes. The active layer of the composite membrane possessing realtively neutral streaming charge and less roughness provided a RO membrane with slowly decreasing flux.

• Membrane and Water Treatment
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• v.4 no.2
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• pp.109-126
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• 2013

Surface modification by low-pressure ammonia ($NH_3$) plasma on commercial thin-film composite (TFC) membranes was investigated in this study. Surface hydrophilicity, total surface free energy, ion exchange capacity (IEC) and zeta (${\zeta}$)-potentials were determined for the TFC membranes. Qualitative and quantitative analyses of the membrane surface chemistry were conducted by attenuated total reflectance Fourier transform infrared (ATR FT-IR) spectroscopy. Results showed that the $NH_3$ plasma treatment increased the surface hydrophilicity, in particular at a plasma treatment time longer than 5 min at 50 W of plasma power. Total surface free energy was influenced by the basic polar components introduced by the $NH_3$ plasma, and isoelectric point (IEP) was shifted to higher pH region after the modification. A ten (10) min $NH_3$ plasma treatment at 90 W was found to be adequate for the TFC membrane modification, resulting in a membrane with better characteristics than the TFC membranes without the modification for water treatment. The thin-film chemistry (i.e., fully-aromatic and semi-aromatic nature in the interfacial polymerization) influenced the initial stage of plasma modification.

• Membrane Journal
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• v.24 no.4
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• pp.292-300
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• 2014

Chlorine-resistant sulfonated poly(arylene ether sulfone) random copolymer (SPAES)-thin film composite (TFC) membranes for desalination are prepared using monoglyme as a selective solvent, which dissolves SPAES, but should be inert to porous polysulfone layer (e.g., Udel$^{(R)}$). Different from formic acid and diethylene glycol used as other selective solvents, monoglyme is environmentally friendly and has much lower boiling temperature. After a pretreatment of Udel$^{(R)}$ support film in isopropyl alcohol-glycerine mixture to minimize pore penetration leading to fairly reduced water flux, coating of SPAES solution in monoglyme onto the support and stepwise drying processes are conducted for defect-free TFC formation. The transport behavior through SPAES-TFC membranes is observed, correlating with the effects of sulfonation level, protonation, and physical and chemical crosslinking of SPAES selective layers.

• Membrane and Water Treatment
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• v.9 no.4
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• pp.211-220
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• 2018

Incorporating nano-materials in thin-film composite (TFC) membranes has been considered to be an approach to achieve higher membrane performance in various water treatment processes. This study investigated the rejection efficiency of three target compounds, i.e., reserpine, norfloxacin and tetracycline hydrochloride, by TFC membranes with different graphene oxide proportions. Graphene oxide (GO) was incorporated into the polyamide active layer of a TFC membrane via an interfacial polymerization (IP) reaction. The TFC membranes were characterized with FTIR, FE-SEM, AFM; in addition, the water contact angle measurements as well as the permeation and separation performance were evaluated. The prepared GO-TFC membranes exhibited a much higher flux ($3.11{\pm}0.04L/m2{\cdot}h{\cdot}bar$) than the pristine TFC membranes ($2.12{\pm}0.05L/m2{\cdot}h{\cdot}bar$) without sacrificing their foulant rejection abilities. At the same time, the GO-modified membrane appeared to be less sensitive to pH changes than the pure TFC membrane. A significant improvement in the anti-fouling property of the membrane was observed, which was ascribed to the favorable change in the membrane's hydrophilicity, surface morphology and surface charge through the addition of an appropriate amount of GO. This study predominantly improved the understanding of the different PA/GO membranes and outlined improved industrial applications of such membranes in the future.

• Proceedings of the Membrane Society of Korea Conference
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• 1999.07a
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• pp.43-47
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• 1999

Pd-ceramic composite membranes and catalytic membrane reactors(CMR) have been studied for hydrogen purification and recovery in th fusion reactor fuel cycle. The development of techniques for coating microporous ceramic tubes with Pd and Pd/Ag layers is described: composite membranes have been produced by electroless deposition (Pd/Ag film of 10-20${\mu}{\textrm}{m}$) and rolling of thin metal sheet (Pd and Pd/ Ag membranes of 50-70 ${\mu}{\textrm}{m}$). Experimental results on electroless membranes showed that the metallic film presented some defects and the membranes had not complete hydrogen selectivity . Then the catalytic membrane reactors with electroless membranes can be applied for some industrial processes that do not require a complete separation of the hydrogen (i.e. in the dehydrogenation of hydrocarbons). The rolled thin Pd/Ag membranes separated the hydrogen from the other gas with a complete selectivity and exhibited a slightly larger (about a factor 1.7) mass transfer resistance with respect to the electroless membranes. Experimental tests confirmed the good performances in terms of durability.

• Korean Membrane Journal
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• v.1 no.1
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• pp.1-7
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• 1999

Pd-ceramic composite membranes and catalytic membrane reactors(CMR) have been studied for hydrogen and its isotopes (deuterium and tritium) purification and recovery in the fusion reactor fuel cycle. Particularly a closed-loop process has been studied for recovering tritium from tritiated water by means of a CMR in which the water gas shift reaction takes place. The development of the techniques for coating micro-porous ceramic tubes with Pd and Pd/Ag thin layers is described : P composite membranes have been produced by electroless deposition (Pd/Ag film of 10-20 $\mu$m) and rolling of thin metal sheets (Pd and Pd/Ag membranes of 50-70 $\mu$m). Experimental results of the electroless membranes have shown a not complete hydrogen selectivity because of the presence of some defects(micro-holes) in the metallic thin layer. Conversely the rolled thin Pd and Pd/ag membranes have separated hydrogen from the other gases with a complete selectivity giving rise to a slightly larger (about a factor 1.7) mass transfer resistance with respect to the electroless membranes. Experimental tests have confirmed the good performances of the rolled membranes in terms of chemical stability over several weeks of operation. Therefore these rolled membranes and CMR are adequate for applications in the fusion reactor fuel cycle as well as in the industrial processes where high pure hydrogen is required (i.e. hydrocarbon reforming for fuel cell)

• Membrane and Water Treatment
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• v.8 no.6
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• pp.613-623
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• 2017

We report the novel thin film composite RO membrane modified by graphene oxide. The thin film composite RO membrane was exposed to 2000 mg/l sodium hypochloride; thereafter it was subjected to different graphene oxide concentration ranging from 50 mg/l to 1000 mg/l in water. The resultant membrane was crosslinked with 5000 mg/l N-hydroxysuccinimide. The performance of different membranes were analysed by solute rejection and water-flux measurement. It was found that 100 mg/l graphene oxide exposure followed by 5000 mg/l N-hydroxysuccinimide treatment resulted in the membrane with the highest solute rejection of 97.78% and water-flux of 4.64 Liter per sqm per hour per bar g. The membranes were characterized by contact angle for hydrophilicity, scanning electron micrographs for surface morphology, energy dispersive X-Ray for chemical composition of the surface, Atomic force microscope for surface roughness, ATR-FTIR for chemical structure identification. It was found that the graphene oxide modified membrane increases the salt rejection performance after exposure to high-fouling water containing albumin. Highly hydrophilic, antifouling surface formation with the nanomaterial led to the improved membrane performance. Moreover, the protocol of incorporating nanomaterial by this post-treatment is simple and can be applied to any RO membrane after it is manufactured.

• Membrane and Water Treatment
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• v.6 no.4
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• pp.309-321
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• 2015

We report in this study the synthesis of mixed matrix reverse osmosis membranes by interfacial polymerization (IP) of thin film nanocomposite (TFNC) on porous polysulfone supports (PS). This paper investigates the synthesis of ZnO nanoparticles (NPs) using the sol-gel processing technique and evaluates the performance of mixed matrix membranes reached by these aerogel NPs. Aqueous m-phenyl diamine (MPD) and organic trimesoyl chloride (TMC)-NPs mixture solutions were used in the IP process. The reaction of MPD and TMC at the interface of PS substrates resulted in the formation of the thin film composite (TFC). NPs of ZnO with a size of about 25 nm were used for the fabrication of the TFNC membranes. These membranes were characterized and evaluated in comparison with neat TFC ones. Their performances were evaluated based on the water permeability and salt rejection. Experimental results indicated that the NPs improved membrane performance under optimal concentration of NPs. By changing the content of the filler, better hydrophilicity was obtained; the contact angle was decreased from $74^{\circ}$ to $32^{\circ}$. Also, the permeate water flux was increased from 26 to 49 L/m2.h when the content of NPs is 0.1 (wt.%) with the maintaining of lower salt passage of 1%.

• Membrane and Water Treatment
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• v.10 no.5
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• pp.381-385
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• 2019

Surface modification is very efficient and scalable approach to achieve improved membrane performance. We treated Reverse Osmosis Thin Film Composite (TFC RO) membrane with various concentrations of Polyethylene Glycol (PEG), a hydrophilic polymer after activation with sodium hypochlorite. This treatment resulted in an increment of the water flux by 43% and the salt rejection by 2.36% for the 3000 mg/l PEG-treated membrane. Further, these PEG-treated membranes were exposed to a mixture of 3000 mg/l PEG and 1000 mg/l sodium hypochlorite for 1 hour. Further modification of this membrane by PEG and sodium hypochlorite mixture increased the water permeance up to 133% when compared with the virgin TFC RO membrane. We characterized the treated membranes to understand the changes in wettability by contact angle analysis, changes in surface morphology and roughness by scanning electron microscope (SEM) and atomic force microscope (AFM) analysis.

• Proceedings of the Membrane Society of Korea Conference
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• 2004.05a
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• pp.170-174
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• 2004

Most of thin film composite reverse osmosis membranes include amide linkages, which are susceptible to chlorine attack resulting in N-chloro derivatives. This study examined a new method based on post-treatment of reverse osmosis membrane with various silane derivatives to improve chlorine resistance. The silane derivatives contain one alkyl group and three alkoxy groups such as trifluoromethyltrimethoxysilane, 3-aminopropylmethoxydiethoxysilane and 3, 3, 3-trifluoropropyltrimethoxysilane. Compared to commercial membranes, silane derivatives coated membranes showed significantly enhanced chlorine durability.