• Membrane Journal
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• v.26 no.6
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• pp.463-469
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• 2016

In this research, a new expectation in enhancing the PES (polyethersulfone) polymer phase inversion membrane performances with nanoparticles is proposed by using ZnO. This paper investigated the synthesis of PES phase inversion membranes including ZnO nanoparticles and evaluates the performance of these mixed matrix membranes. The PES-ZnO mixed matrix membranes were fabricated by phase inversion method using the PES-ZnO-NMP(N-methyl-1-pyrrolidone) casting solutions with low ZnO nanoparticles content of 0.375 wt%. The influence of ZnO nanoparticles on the characteristics of PES-ZnO mixed matrix membranes was investigated with scanning electron microscope observations of membrane cross-sections, contact angle measurements, tensile strength measurements, pure water flux measurements and ultrafiltration experiments of BSA solution. Those results showed that the performance advancements in comparison with the pure PES membrane without ZnO in terms of increasing hydrophilicity as well as reducing membrane fouling by adding ZnO nanoparticles even in low concentration.

• Membrane and Water Treatment
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• v.11 no.2
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• pp.131-139
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• 2020

The current study focused on the preparation of low-cost PVC-based adsorbing membrane. Metakaolin, as available adsorbent, was embedded into the PVC matrix via solution blending method. The as-prepared PVC/metakaolin mixed matrix membranes were characterized using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy, atomic force microscopy (AFM), pure water permeability and contact angle measurements. The results confirmed the improvement of PWP and hydrophilicity due to the presence of metakaolin in the PVC matrix. Additionally the structure of PVC membrane was changed due to the incorporation of metakaolin in the polymer matrix. The static adsorption capacity of all samples was determined through dye removal. The effect of metakaolin dosage (0-7%) and pH (4, 8, 12) on dye adsorption capacity was investigated. The results depicted that the highest adsorption capacity was achieved at pH of 4 for all samples. Additionally, adsorption data were fitted on Langmuir, Freundlich, and Temkin models to determine the appropriate governing isotherm model. Finally, the dynamic adsorption capacity of the optimum PVC/metakaolin membrane was studied using dead-end filtration cell. The dye removal efficiency was determined for pure PVC and PVC/metakaolin membrane. The results demonstrated that PVC/metakaolin mixed matrix membrane had a high adsorption capacity for dye removal from aqueous solution.

• Korean Membrane Journal
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• v.7 no.1
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• pp.67-70
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• 2005

It is well known as the role of ion exchange membrane with functional group in membrane matrix. Recently, we were reported that the charged mosaic membrane within parallel array of negative and positive charge groups. In this study we are reported the properties for the various transport coefficients of metal and heavy metal ions across charged mosaic membrane based on non-equilibrium thermodynamics is not based on equilibrium state.

• Membrane and Water Treatment
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• v.9 no.2
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• pp.105-113
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• 2018

Maillard reaction products like melanoidins present in industrial fermentation wastewaters are complex compounds with various functional properties. In this work, novel ultrafiltration (UF) mixed matrix membrane (MMM) composed of polysulfone (PSF) and nanocomposites was prepared through a phase inversion process for the recovery of melanoidins. Nanocomposites were prepared with acid functionalized multiwalled carbon nanotubes (MWCNTs) as the reinforcing filler for chitosan-thermoplastic starch blend. Higher nanocomposites content in the PSF matrix reduced the membrane permeability and melanoidins retention indicating tighter membrane with surface defects. The membrane surface defects could be sealed with dilute polyvinyl alcohol (PVA) solution. The best performing membrane (1% nanocomposites in 18% PSF membrane sealed with 0.25% PVA coating) resulted in uniform melanoidins retention of 98% and permeability of 3.6 L/m2 h bar over a period of 8h. This demonstrates a low fouling PSF membrane for high melanoidins recovery.

• Journal of Industrial and Engineering Chemistry
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• v.67
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• pp.156-163
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• 2018

High-performance mixed-matrix membranes that comprise both zeolitic imidazolate framework-8 (ZIF-8) and graphene oxide (GO) were synthesized with a solution casting technique to realize excellent $CO_2/CH_4$ separation. The incorporation of ZIF-8 nanocrystals alone in ODPA-TMPDA polyimide can be used to significantly enhance $CO_2$ permeability compared with that of pure ODPA-TMPDA. Meanwhile, the addition of a GO nanostack alone in ODPA-TMPDA contributes to improved $CO_2/CH_4$ selectivity. Hence, a composite membrane that contains both fillers displays significant enhancements in $CO_2$ permeability (up to 60%) and $CO_2/CH_4$ selectivity (up to 28%) compared with those of pure polymeric membrane. Furthermore, in contrast to the ZIF-8 mixed-matrix membrane, which showed decreased mechanical stability, it was found that the incorporation of GO could improve the mechanical strength of mixed-matrix membranes. Overall, the synergistic effects of the use of both fillers together are successfully demonstrated in this paper. Such significant improvements in the mixed-matrix membrane's $CO_2/CH_4$ separation performance and mechanical strength suggest a feasible and effective approach for potential biogas upgrading and natural gas purification.

• Structural Engineering and Mechanics
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• v.5 no.5
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• pp.599-608
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• 1997

The concrete stiffness matrices of membrane elements used in the finite element analysis of wall-type structures are reviewed and discussed. The behavior of cracked reinforced concrete membrane elements is first described by summarizing the constitutive laws of concrete and steel established for the two softened truss models (the rotating-angle softened-truss model and the fixed-angle softened-truss model). These constitutive laws are then related to the concrete stiffness matrices of the two existing cracking models (the rotating-crack model and the fixed-crack model). In view of the weakness in the existing models, a general model of the matrix is proposed. This general matrix includes two Poisson ratios which are not clearly understood at present. It is proposed that all five material properties in the general matrix should be established by new biaxial tests of panels using proportional loading and strain-control procedures.

• Membrane and Water Treatment
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• v.7 no.4
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• pp.367-375
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• 2016

Although the bucky paper (BP) made from carbon nanotubes (CNTs) possesses beneficial characteristics of hydrophobic nature and high porosity for membrane distillation (MD) application, weak mechanical strength of BP has often prevented the stable operation. This study aims to fabricate the BP with high mechanical strength to improve its MD performance. The strategy was to increase the purity level of CNTs with an assumption that purer CNTs would increase the Van der Waals attraction, leading to the improvement of mechanical strength of BP. According to this study results, the purification of CNT does not necessarily enhance the mechanical strength of BP. The BP made from purer CNTs demonstrated a high flux ($142kg/m^2{\cdot}h$) even at low ${\Delta}T$ ($50^{\circ}C$ and $20^{\circ}C$) during the experiments of direct contact membrane distillation (DCMD). However, the operation was not stable because a crack quickly formed. Then, a support layer of AAO (anodic aluminum oxide) filter paper was introduced to reinforce the mechanical strength of BP. The support reinforcement was able to increase the mechanical strength, but wetting occurred. Therefore, the mixed matrix membrane (PSf-CNT) using CNTs as filler to polysulphone was fabricated. The DCMD operation with the PSf-CNT membrane was stable, although the flux was low ($6.1kg/m^2{\cdot}h$). This result suggests that the mixed matrix membrane could be more beneficial for the stable DCMD operation than the BP.

• Journal of Korean Society of Water and Wastewater
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• v.22 no.4
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• pp.437-444
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• 2008

Many other countries have investigated the new backwash water treatment process to save the existing water resource. There are various methods for reusing backwash water, but the membrane system has received the most interest for its efficiency. The objective of this study was to certify the application of membrane filtration system for the backwash water treatment. The experiment equipment was composed of Lab scale tubular membrane filtration system. Generally, cross-flow operation mode is used in the tubular membrane system but cross-flow operation mode demands high electric cost mainly for the pump energy. So to cut off electric cost, dead-end operation mode was used in this experiment. Filtration and bleed operation cycle was used in this membrane system. Backwash water was concentrated during the filtration process and when backwash water reached our target suspended solid concentration, it was discharged from this system. For efficient operation of filtration and bleed, mathematical matrix was drawn up and with this matrix we could simulate various sets of filtration and bleed time.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.31 no.3
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• pp.216-221
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• 2009

Purpose: The retention of the basement membrane complex, which was the unique feature of the acellular dermal matrix ($AlloDerm^{(R)}$), plays an important role in the normal process of wound healing. The present study was aimed to compare the healing of the acellular dermal matrix according to the graft method in the rabbit ear. Materials and methods: Six mature rabbits weighing about 3.0 kg were used, $10\;{\times}\;5\;mm$ sized subcutaneous pockets were created between the ear skin and the underlying perichondrium. In the control group, the acellular dermal matrix was grafted with the basement membrane facing toward the perichondrium. On the contrary, the acellular dermal matrix was grafted with the basement membrane facing toward the skin side in the experimental group I. In the experimental group II, the acellular dermal matrix was grafted like rolled configuration with basement membrane side in. The grafted site was picked at 3, 7, and 21 days after the graft. Serial sections were processed by H-E stain and examined under light microscopy to assess the healing patterns. Results: There was no distinct volume loss in the gross examination, but resorption was observed from the edge of the acellular dermal matrix in the histological examination. The space of resorption was replaced by the newly formed fibrous tissues and vessels. The inflammatory cells were more increased at 7 days after the graft than the early days. However, inflammation was decreased at 21 days after the graft. Regardless of the graft direction, no differences were observed between the control and the experimental group I in the healing patterns. Conclusion: These results suggest that the acellular dermal matrix can be used simply and effectively without regard to the graft direction as a substitute of autogenous material for repairing soft tissue defect.

• Membrane Journal
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• v.31 no.6
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• pp.434-442
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• 2021

Poly(vinylidene fluoride) (PVDF) membrane has a good membrane durability because of its high mechanical resistance, thermal and chemical stability. However, the strong hydrophobic property of PVDF membrane can induce a low water permeability and easy fouling by proteins and organic matters. In order to improve the anti-fouling properties of PVDF membrane, the PVDF mixed matrix asymmetric membranes impregnated with biofunctional material 𝛽-cyclodextrin (𝛽-CD) in the membrane structure were prepared by phase inversion method. The membrane filtration experiments of pure water and BSA solution were performed using the PVDF/𝛽-CD mixed matrix asymmetric membranes prepared according to the 𝛽-CD contents. The experiments showed that the introduction of 𝛽-CD into the PVDF polymer matrix contributed to increase in the hydrophilic property of the PVDF membranes, and this led to the reduction of contact angles and improvement of anti-fouling properties. The PVDF/𝛽-CD membrane which was prepared using the dope solution with a 2 wt% 𝛽-CD content represented 64 L/m²·h of pure water flux, 95% of BSA rejection and maximum 80% of flux enhancements compared to flux results of the pristine PVDF membrane.