Abstract <p>The work contains studies on increasing the porosity of the surface layer of composite membranes. In order to increase the porosity of composite membranes, such solvents as ethanol and acetonitrile, whose boiling point is higher than that of acetone, which was used as the main cellulose acetate, were added to the polymer solution as a porogen. Based on the results of the study, samples of composite membranes were obtained and their physicochemical properties, such as total porosity, layer thickness, water absorption, and wetting angle, were studied and IR spectra of the membranes were obtained. The specific productivity and retention capacity of the obtained microfiltration membranes were also established.</p>