Occlusion of pores of polymeric membranes with colloidal silica

Moaddeb, Maryam; Koros, William J.

doi:10.1016/s0376-7388(97)00165-8

Cited by 14 publications

(7 citation statements)

References 2 publications

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“…Nevertheless, we feel a more probable cause for these deviations is due to inhibition of polymer chain mobility near the sieve−polymer interface, because of polymer adsorption onto the surface of the sieve. This effect has been seen by previous researchers working on related problems and could lead to reduced permeability around the interface. This effect, in turn, would lead to a reduced overall permeability.…”

Section: Poly(vinyl Acetate) Mixed-matrix Membranesmentioning

confidence: 99%

Factors Controlling Successful Formation of Mixed-Matrix Gas Separation Materials

Mahajan

Koros

2000

Ind. Eng. Chem. Res.

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488

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Prior work has suggested simple guidelines for matching transport characteristics of materials to form high-performance mixed-matrix materials for gas separation. Such materials comprise a dispersion of molecular sieving particles in a properly selected matrix polymer phase. Recent work has shown that these simple criteria are necessary but not sufficient to achieve the desired properties. The analysis presented here shows the need to optimize the transport properties of the interfacial region, i.e., the region between the bulk polymer and dispersed sieve phases. Guided by the need to optimize both the transport properties of the interfacial region and the matrix material selection criteria noted above, a new paradigm is recommended for matrix phase selection. The practicality of the paradigm is validated by the formation of mixed-matrix membranes with an appropriate polymer and sieve. These materials lead to the attractive predicted performances at low loading. For success at higher loading a zeolite "priming" protocol based on polymer-solvent sieve interactions is shown to be necessary. This modified protocol leads to success at intermediate and high dispersed-phase loading.

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Section: Poly(vinyl Acetate) Mixed-matrix Membranesmentioning

confidence: 99%

Factors Controlling Successful Formation of Mixed-Matrix Gas Separation Materials

Mahajan

Koros

2000

Ind. Eng. Chem. Res.

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488

343

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“…HA coated particles were more stable than FA coated particles. Moaddeb and Koros (1997) described the deposition of silica on polymeric MF membranes as nonuniform. This means that cake characterisation is difficult as a cracks could vary the results.…”

Section: Microfiltrationmentioning

confidence: 99%

Natural Organics Removal Using Membranes

Schäfer¹

2001

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Membrane processes are increasingly used in water treatment. Experiments were performed using stirred cell equipment, polymeric membranes and synthetic surface water containing natural organics, inorganic colloids and their aggregates, and cations.All processes could remove a significant amount of natural organics. Pretreatment with ferric chloride was required to achieve significant organic removal with MF and high MWCO UF.Additionally, fouling mechanisms for the three processes were investigated. Crucial parameters were aggregate characteristics (fractal structure, stability, organic-colloid interactions), solubility of organics and calcium, and hydrodynamics.

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“…For example, methods have been reported that consist of depositing different oxide thin films by thermal chemical vapor deposition ͑CVD͒ or the impregnation with colloidal SiO 2 particles. [36][37][38][39][40] The deposition of either compact or porous SiO 2 thin films by PECVD according to the present procedure may be an interesting alternative to these methods, particularly when no heating step during preparation is required. In this sense, it could also be expected that our method, furnishing an arrangement of pores perpendicular to the surface, could be an alternative to the anodic oxidation used commercially for the synthesis of supports with controlled permeability.…”

Section: ϫ9mentioning

confidence: 99%

Room temperature synthesis of porous SiO2 thin films by plasma enhanced chemical vapor deposition

Barranco

Cotrino

Yubero

et al. 2004

Journal of Vacuum Science &Amp; Technology A: Vacuum, Surfaces, and Films

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Silicon dioxide thin films with variable and controlled porosity have been prepared at room temperature by plasma enhanced chemical vapor deposition in an electron cyclotron resonance microwave reactor with a downstream configuration. The procedure consists of the deposition of successive cycles consisting of a sacrificial organic-polymeric layer and, afterward, a silicon dioxide layer. Toluene and oxygen are used as precursors of the organic layers and Si(CH 3 ) 3 Cl and oxygen for the SiO 2 . During deposition of the latter, the organic layer is simultaneously burned off. In these conditions, the release of gases produced by oxidation of the organic-polymeric layer take place while the oxide layer is being deposited. Thus, modification of the nucleation and growing mechanism of the silicon oxide thin film take place. The porosity of the final porous SiO 2 thin films increases with the thickness of the sacrificial organic layer. The porous SiO 2 films prepared with the aforementioned method are free of carbon and chlorine contamination as confirmed by Fourier-transform infrared spectroscopy, x-ray photoelectron spectroscopy, and Rutherford backscattering spectroscopy. Depending on their porosity, the SiO 2 thin films are either transparent or scattered visible light. The former have refractive index lower than that of thermal silicon dioxide and the latter show membranelike behavior in gas diffusion experiments. All the samples have good adhesion to the substrates used for the deposition, either polished Si wafer, glass plates, or standard porous supports. They have columnar microstructure, as determined by scanning electron microscopy. A preliminary ultraviolet-visible characterization of the optically transparent thin films reveals that transmission of light through glass increases by 7%-8% when the porous silica is deposited on this substrate. These films prove to be very efficient as antireflective coatings and are of interest for photovoltaic and similar applications. It is possible to deposit SiO 2 thin films with densities as low as 0.65 g/cm 3 ͑corresponding to a porosity of 70%͒ by adjusting the thickness of the sacrificial and SiO 2 layers. The films with high porosity are promising materials for the fabrication and/or modification of diffusion membranes. The gas adsorption properties and the type of porosity of the SiO 2 thin films are assessed by adsorption isotherms of toluene at room temperature measured with a quartz crystal monitor device. The gas permeation properties of the films ͑when used as membranes͒ are analyzed by studying the diffusion rate of different gases through them.

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Occlusion of pores of polymeric membranes with colloidal silica

Cited by 14 publications

References 2 publications

Factors Controlling Successful Formation of Mixed-Matrix Gas Separation Materials

Factors Controlling Successful Formation of Mixed-Matrix Gas Separation Materials

Natural Organics Removal Using Membranes

Room temperature synthesis of porous SiO2 thin films by plasma enhanced chemical vapor deposition

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