Identification of pores of ultrafiltration membranes based on electron microscopic studies
The study analyses methods, modes, techniques, and applications for the identification of pores in polymer membranes. Based on a comparison of the advantages and disadvantages of the methods, an approach to the development of the software for the study of the pores of polymeric semipermeable membranes is proposed. The objects of the study were UAM-50, UAM-100, UPM-K, and UPM-100 type ultrafiltration membranes, the choice of which was provided by high retention capacity, good performance and the high applicability in industrial practice. A method for the calculation of the membrane contamination coefficient, allowing to determine the period of effective operation of ultrafiltration membranes, elements and installations for baromembrane and electrobaromembrane separation, concentration and purification of industrial solutions and effluents is presented. Selected sections of ultrafiltration UAM-50, UAM-100, UPM-K, and UPM-100 membranes with an area of 1.000.000 nm<sup>2</sup> were processed using Matlab 2017 in such a way that the main parameters, such as the average contamination diameter (pore diameters and membrane contamination factor) were obtained. For processing large data sets on the average pore diameters and the membrane contamination coefficient, a PC was used. The use of PC allowed to reduce and calculate the error of the measurements performed using standard methods of mathematical statistics. The calculation of the membrane contamination coefficient was carried out using a program studying the description of the main functions of the imaging processing toolbox. The developed method significantly reduced the time of the experiment and allowed automatically calculate the number of objects, average area, and pore diameter on the sorption surface. The method combining electron microscopic studies, image processing using Otsu's method, software implementation in Matlab 2017, provides possibility to obtain reliable and reproducible data on the surface morphology of ultrafiltration UAM-50, UAM-100, UPM-K, and UPM-100 membranes, based on statistical processing of a large sample of data obtained as a result of electron microscopic studies. Analysis of the experimental data obtained by the automated method showed that the average area of the object was the smallest for the UPM-K membrane and the largest for the UAM-50 membrane, and the average pore diameter of the surface of the studied membranes was in the range from 51 to 60 nm, which was comparable with results obtained by other methods and described in the literature. At the same time, the contamination coefficient was higher for the UPM-K membrane and lower for the UPM-100 membrane.