Abstract
The chemical composition, physical structure and morphology of interfacially formed composite membranes were studied by a variety of surface science techniques, including attenuated total reflectance infrared spectrometry (ATR-IR), Rutherford backscattering spectroscopy (RBS), Xray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). These techniques allow the characterization of ultrathin membrane barrier layers, as opposed to many techniques which are used only to study bulk samples. Also, the membrane performance was determined in reverse osmosis using a 5% aqueous isopropanol feed stream. p]The thickness of the barrier layer could be readily determined by microscopic techniques; however, this measurement may be in error due to penetration of the barrier layer into the porous support. By using a heavy metal dye which preferentially stained the barrier layer, TEM studies clearly showed the extent of this interpenetration. The chemical species present in the barrier layer were best characterized by ATR-IR and RBS techniques, since these are not as sensitive as XPS to surface contamination. RBS was particularly effective because it also provides a nondestructive determination of the element gradients within the top few microns of the sample. p]This type of study with complementary surface science techniques is especially needed for the study of composite materials which are formed in situ, because the chemical structure can be very complex and different from that of bulk reactions. Extensive characterization by a variety of methods can provide greater certainty for drawing conclusions about structure-performance relationships.
Published Version
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