Visualisation of an ultrafiltration membrane by non-contact atomic force microscopy at single pore resolution (original) (raw)
Related papers
Journal of Membrane Science, 1996
Non-contact atomic force microscopy has been used to investigate the surface pore structure of Cyclopore and Anopore microfiltration membranes in air. Three Cyclopore membranes and three Anopore membranes of different pore sizes were studied. Excellent high resolution images were obtained. Analysis of the images gave quantitative information on the surface pore structure, in particular the pore size distribution. Non-contact AFM is an excellent means of obtaining such information for microfiltration membranes.
An AFM Study of Ultrafiltration Membranes: Peculiarities of Pore Size Distribution
Petroleum Chemistry
The Mifil ultrafiltration membrane made from aromatic polyamide PA�100 has been studied using a SmartSPM�1000 atomic force microscope (AIST�NT, Zelenograd, Russia). Pores on the AFM images have been identified using the Gwyddion software in two ways, by threshold and watershed methods. The pore size data have been subjected to statistical processing and interpretation. Along with the log�normal pore�size distribution law, a bimodal curve of a special kind has been considered. The accuracy of the approximation has been assessed using Pearson’s goodness of fit test, in which the bimodal distribution has demonstrated better agreement with the experimental data. It has been shown that the watershed method provides more detailed information about the pore size distribution of the investigated membrane.
Applied Physics A-materials Science & Processing, 2001
The surfaces of three commercial urea formaldehyde polysulfone membranes from Dow DenmarkTM (GR51, GR61 and GR81) are characterised both topographically and chemically. Their topography is studied by scanning force microscopy to obtain the corresponding pore-size distributions, which are in fair agreement with nominal molecular weight cut-offs. The composition of the surfaces of the membranes is analysed by X-ray photoelectron spectroscopy. The resulting percentage content of nitrogen, which could be attributed probably to an additive used in the manufacturing process, is shown to correlate with the portion of the total surface with different viscoelastic properties as investigated by using phase-contrast scanning force microscopy. Both parameters are increasing for membranes with decreasing molecular weight cut-off. Also, the additive seems to be more sparsely distributed for the membranes with bigger pores, according to fractal analysis. Finally, all the membranes are very similarly wettable.
Journal of Membrane Science, 2004
Hollow fiber membranes for hemodialysis were prepared from polyethersulfone (PES) and poly(vinyl pyrrolidone) (PVP) (PES/PVP=18/3 and 18/6 by weight) solution in N,N-dimethylacetamide by the dry wet spinning method. Hollow fibers were then heated either in hot water (95 °C for 30 min) or in air (150 °C for 5 min). These membranes were characterized by ultrafiltering dextrans of different molecular weights (200 ppm in water) at room temperature and an operating pressure of 5 psig. It was observed that the water flux of the hollow fiber increased significantly when heat-treated in water, while decreased when heat-treated in air. On the other hand, molecular weight cut-off (MWCO) of the hollow fiber increased slightly when heat-treated in water, while decreased drastically when heat-treated in air. The morphology of the surfaces of the hollow fibers was studied by atomic force microscope (AFM) in terms of surface roughness. The roughness of both inner and outer surface decreased upon heat-treatment, either heated in water or in air. The membrane heat-treated in air exhibited the lowest roughness parameter. SEM images also showed that the surface morphology of membranes was different before and after heat-treatment. Discussions are made on the basis of MWCO and AFM results. The performance data of the hollow fiber heated in air at 150 °C was found to be the most appropriate for hemodialysis application. The hollow fiber membrane prepared from the blend ratio of PES/PVP=18/3 showed slightly higher flux than the hollow fiber membrane prepared from a solution with PES/PVP ratio of 18/6.
Atomic force microscope studies of membranes: force measurement and imaging in electrolyte solutions
Journal of Membrane Science, 1997
An atomic force microscope has been used to study the electrical double layer interactions between a silicon tip (with an oxidised surface) and two polymeric membranes, one microfiltration (nominally 0.1 μm) and the other ultrfiltration (25 000 MWCO), in aqueous NaCl solutions. Force-distance curves were measured for the two membranes at four ionic strengths. The membranes were also imaged under the same conditions using electrical double layer repulsive forces of differing magnitudes —; “electrical double layer mode” imaging. Image analysis was used to determine surface pore size distributions. The force-distance curves, together with numerically calculated potential profiles at the entrance to a charged pore, allow an explanation and identification of the optimum imaging conditions. The best images were obtained at high ionic strength with the tip close to the membrane surface.