This review is devoted to the application of bulk synthetic polymers such as polysulfone (PSf), polyethersulfone (PES), polyacrylonitrile (PAN), and polyvinylidene fluoride (PVDF) for the separation of oil-water emulsions. Due to the high hydrophobicity of the presented polymers and their tendency to be contaminated with water-oil emulsions, methods for the hydrophilization of membranes based on them were analyzed: the mixing of polymers, the introduction of inorganic additives, and surface modification. In addition, membranes based on natural hydrophilic materials (cellulose and its derivatives) are given as a comparison.

A synthetic method has been used to measure the bubble-point pressures of carbon dioxide (CO₂) and methane (CH₄), for a temperature range of 303.15–363.15 K and for pressures up to 14 MPa, in the following ionic liquids: 1-ethyl-3-methylimidazolium diethylphosphate [emim][dep], trihexyltetradecylphosphonium bis(2,4,4-trimethylpentyl)phosphinate [thtdp][phos], trihexyltetradecylphosphonium dicyanamide [thtdp][dca], 1-allyl-3-methylimidazolium dicyanamide [amim][dca], 1-butyl-1-methylpyrrolidinium dicyanamide [bmpyrr][dca], 1,2,3-tris(diethylamino)cyclopropenylium dicyanamide [cprop][dca], 1,2,3-tris(diethylamino)cyclopropenylium bis(trifluoromethylsulfonyl)imide [cprop][Tf₂N], 1-butyl-1-methylpiperidinium bis(trifluoromethylsulfonyl)imide [bmpip][Tf₂N], triethylsulfonium bis(trifluoromethylsulfonyl)imide [tes][Tf₂N], and methyltrioctylammonium bis(trifluoromethylsulfonyl)imide [toa][Tf₂N]. The solubility of CH₄ on mole fraction basis is a factor of 10 lower than that of CO₂ at similar conditions. Henry constants of CO₂ and CH₄ in all the ionic liquid (IL) systems are presented, from which the ideal CO₂/CH₄ selectivities are obtained. The ideal CO₂/CH₄ selectivities of the investigated ILs are in the range of the conventional solvents like Selexol, Purisol, Rectisol, Fluor Solvent, and sulfolane. The ideal CO₂/CH₄ selectivity decreases dramatically with increasing temperature and increasing IL molecular weight. Furthermore, the experimental data has been modeled accurately with the Peng–Robinson equation of state in combination with van der Waals mixing rules.

Gas-liquid membrane contactors that were based on hollow fiber membranes are the example of highly effective hybrid separation processes in the field of membrane technology. Membranes provide a fixed and well-determined interface for gas/liquid mass transfer without dispensing one phase into another while their structure (hollow fiber) offers very large surface area per apparatus volume resulted in the compactness and modularity of separation equipment. In many cases, stated benefits are complemented with high separation selectivity typical for absorption technology. Since hollow fiber membrane contactors are agreed to be one of the most perspective methods for CO₂ capture technologies, the major reviews are devoted to research activities within this field. This review is focused on the research works carried out so far on the applications of membrane contactors for other gas-liquid separation tasks, such as water deoxygenation/ozonation, air humidity control, ethylene/ethane separation, etc. A wide range of materials, membranes, and liquid solvents for membrane contactor processes are considered. Special attention is given to current studies on the capture of acid gases (H₂S, SO₂) from different mixtures. The examples of pilot-scale and semi-industrial implementation of membrane contactors are given.