Īn interesting way to accomplish such modification of membranes is the treatment of membranes with surfactants. The flow recovery after flushing was 92%. The membranes showed an efficiency of 99.9% in the separation of oil-water emulsions and a diesel-in-water emulsion permeability of 314 L ∙m −2∙h −1∙bar −1. The introduction of candle soot (i.e., a source of monodisperse carbon nanoparticles) into the membrane matrix made it possible to significantly increase the resistance to pollution. Another much cheaper membrane modifier is candle soot. Changes in membrane morphology were confirmed by electron microscopy data. The water permeability of the membranes increased from 39 to 573 L∙m −2∙h −1∙bar −1, and the oil retention reached almost 100%. The authors obtained membranes with high hydrophilicity: the contact angle of wetting the surface of the original membrane was 69.5°, and that of the modified one was 16.4°. The work presents the modification of hollow fiber membranes made of polyethersulfone by introducing particles of hydrophilic magnesium dihydroxide into the surface layer of the fiber. In addition, some focus on the application of natural polymers is also given due to current trends in “green” chemistry and sustainable developments. Various approaches to the hydrophilization of filtration membranes made of PSf, PES, PVDF, and PAN are discussed in order to increase their separating ability and pollution resistance. Bearing this in mind, this review is devoted to the production of membranes for the separation of oil-water emulsions based on commercial synthetic polymers (PSf, PES, PVDF, PAN) by the phase-inversion method. Thus, the hydrophilization of the surface and/or bulk of the membrane can be considered as a perspective approach to reduce the contamination of commercial membranes made of bulk polymers. Such phenomena can be explained by the formation of a dense hydrated layer on the membrane surface, which reduces the direct contact and, hence, the adhesion of pollutants to the polymer. Numerous studies have shown that membranes with superhydrophobic and superoleophobic surfaces demonstrate the best resistance towards oil pollution. The schematic illustration of the formation of the porous membrane by the NIPS method is given in Scheme 1. The most common is the NIPS method, when the polymeric solution is separated into two phases, polymer-rich and solvent-rich ones, due to the interaction with non-solvent (typically, water) once the formed polymeric film is in the precipitation bath. The porous structure of MF/UF membranes is formed as a result of phase inversion of polymeric solution : thermally induced phase separation (TIPS), evaporation induced phase separation (EIPS), vapor induced phase separation (VIPS), non-solvent induced phase separation (NIPS), or a combination of these methods. The commercial UF and MF membranes are typically fabricated from a number of bulk polymers, particularly polysulfone (PSf), polyethersulfone (PES), polyvinylidene fluoride (PVDF), and polyacrilonitrile (PAN). However, its further application is partially hindered by the high capital costs required for large volumes of effluent and the fouling/degradation of the polymeric membranes during long-term operation. The membranes show a number of advantages over other methods such as the high efficiency of separation of fine water-oil emulsions, the absence of additional chemicals, high separation capacity, energy efficiency, compactness, and modularity of equipment. Considering the last one, it can be seen from Figure 1 that the number of publications on the application of membrane for the separation of the oil-water emulsion has been increased by a factor of five during the last ten years. To overcome this problem, a number of methods have been developed to breakdown such stable oil-water emulsions: chemical, biological, mechanical (cyclones, separators, settling tanks, centrifuges), thermal, microwave, electrical, ultrasonic, and membrane separation. However, the complete cleaning of water from the presence of the oil is complicated by the formation of oil-water emulsions, which become more stable due to the presence of different components in the oil or to water acting as emulsifiers such as asphaltenes, resins, mineral salts, clay particles, etc. In the case of oil-polluted surface waters, there are a big variety of adsorbents traditionally used to collect the excess of the oil, including sponges, foam materials, and natural adsorbents. The exploration, production, transportation, and refining of crude oil are always associated with the separation of water-oil mixtures as the primary stage of oil refining or due to the accidents resulting in the oil spilling.

454 water in oil emulsion