Preparation and properties of novel organic–inorganic porous membranes

doi:10.1016/S1383-5866(00)00127-1

Separation and Purification Technology

Volumes 22–23, 1 March 2001, Pages 269-275

https://doi.org/10.1016/S1383-5866(00)00127-1 Get rights and content

Abstract

This paper deals with the preparation and characterization of novel organic–inorganic composite membranes formed by fine silica particles uniformly dispersed in the porous matrix of poly(vinylidene fluoride). Membranes were prepared by phase inversion process and were characterized by ultrafiltration (UF) experiments, burst pressure tests and scanning electron microscope (SEM) observations. Spectroscopic (FTIR-ATR, FT-Raman) and calorimetric (DSC) measurements were also carried out in order to investigate interactions between membrane components. Supported membranes were finally prepared and their ultrafiltration performance was compared with that of unsupported ones.

Introduction

The preparation of membranes formed by inorganic particles uniformly dispersed in a polymer matrix has received much attention from several years. The studies, mainly focused on gas separation [1], [2], [3] and pervaporation membranes [4], [5], [6] have been recently extended to porous membranes for ultrafiltration and potential nanofiltration properties [7].

In this presentation the first results of a research aimed at obtaining new membranes that exhibit typical thermal stability and chemical inertia of fluorocarbon polymers along with new properties given from the presence of inorganic particles with proper chemical and physical characteristics are reported. In particular this presentation deals with poly(vinylidene fluoride)-silica ultrafiltration membranes prepared by phase inversion technique starting from controlled dispersions of fine inorganic silica particles in polymer solutions. Silica particles were selected not only for their chemical stability, very similar to that of the PVDF, especially as far as pH resistance is concerned, but also for their good compatibility with organic solvent used to prepare PVDF solutions [8]. This latter fact allowed very stable dispersion to be obtained, without any settling or aggregation phenomena, and, hence to prepare very homogeneous membranes with a very uniform particles distribution into the polymer structure.

Section snippets

Materials

The PVDF used was a commercial product (Foraflon 1000HD, Atochem). N,N-dimethylformamide (DMF, 99.8%, A.C.S. reagent, Aldrich) and N-methyl-2-pyrrolidone (NMP, 99+%, A.C.S. reagent, Aldrich) were used as polymer solvents. Silica particles (silica fumed, 99.8%, Aldrich) with nominal size of 0.014 μm were used as additive for PVDF solutions. A polypropylene non-woven (Viledon, FO-2430, Freudenberg) was used for preparing supported membranes. Dextran with nominal average molecular mass of 40.000

Results and discussion

Binary solutions of PVDF and NMP were clear and had viscosities ranging from ca. 400 to ca. 8200 mPa s depending on the polymer concentration (Fig. 1). Dispersion of the particles in NMP gave clear or slightly opalescent silica sols whose viscosities are reported in Fig. 2. Fig. 3 refers to ternary dispersions and shows the behaviour of the viscosity as a function of the amount of silica incorporated into PVDF solutions of different polymer concentration. As it can be seen the addition of

Conclusions

The effect of addition of fine silica particles to PVDF casting solution on some properties of the resulting composite membranes has been investigated. The preliminary results indicate that the thermal properties of the PVDF/silica composite membranes are very similar to those of the PVDF membranes while the mechanical resistance is slightly lower. Increasing amounts of silica added to more diluted PVDF solutions yield membranes with higher permeate flux and lower retention while no particular

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Preparation and properties of novel organic–inorganic porous membranes

Abstract

Introduction

Section snippets

Materials

Results and discussion

Conclusions

J. Membrane Sci.

J. Membrane Sci.

J. Membrane Sci.

J. Membrane Sci.

Filtration and Separation

J. Membrane Sci.