A Study of the Surface Morphology of Microfiltration Membranes of the MFFK and MPS Brands by Atomic-Force- and Scanning-
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y of the Surface Morphology of Microfiltration Membranes of the MFFK and MPS Brands by Atomic-Force- and ScanningElectron Microscopy S. V. Kovaleva, *, S. I. Lazareva, and O. A. Kovalevaa aTambov
State Technical University, Tambov, 392000 Russia *e-mail: [email protected]
Received December 12, 2019; revised January 25, 2020; accepted January 27, 2020
Abstract—The methods of atomic-force- and scanning-electron microscopy are used to study the surface morphology of polymeric microfiltration membranes. Commercial membranes of the MFFK (on the basis of a hydrophobic fluoroplastic composite membrane, pore size of 0.45 μm) and MPS (polyethersulfone membrane, pore size of 0.45 μm) brands produced by OOO NPP Tekhnofil’tr (Vladimir, Russia) are used as the objects of study. A mature molasses brew produced by OAO Biokhim (Rasskazovo, Tambov Oblast) is used as the technological fluid for the working samples of MFFK and MPS membranes in the microfiltration process. An analysis of the surface morphology of the microfiltration membranes makes it possible to determine the regions of the location of pores, yeast, and polysaccharides, and the interpore connecting regions. By analyzing microscopic images, the flow lines of the solution to be separated are revealed in the profile hollows on the surface of the working microfiltration membranes. The initial MFFK and MPS membranes are found to have slit pores (0.4–0.6 μm in length and width), and the working membranes are contaminated (clogged) by yeast, polysaccharides, and their fragments, which is associated with residual dynamic membrane formation. The surface-roughness parameters of the working MFFK and MPS membranes are shown to be different: the Ra and Rz values differ by factors of 1.69 and 1.87, respectively; and the Rmax values in the case of oblique and frontal sections differ by factors of 1.67 and 1.05, respectively. This is explained by the specific features accompanying the process of the microfiltration separation of solutions containing yeast, polysaccharides, and their fragments (the presence of an adsorption layer on the membrane surface and cracks in the residual layer of the dynamic membrane, i.e., the clogged layer). Keywords: atomic-force microscopy, scanning-electron microscopy, surface, morphology, microfiltration membrane DOI: 10.1134/S1027451020040126
INTRODUCTION The methods of atomic-force- (AFM) and scanning-electron microscopy (SEM) are widely used to study the surface morphology of organic and inorganic membranes [1–3]. In [4], the surface morphology of MF-4SK membranes in the initial state and after modification with polyaniline was studied. It was shown that the AFM method allows one to characterize qualitative and quantitative changes in the surface topography of the membranes. In [5], it was noted that the sorption of pectin on MA-40 and MA-41 membranes, respectively, increases and decreases the surface uniformity using the AFM method. The use of AFM for studying the porous structure of cationexchange membranes was considered in [6]. Based on experimen
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