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.