In recent years, increased attention has been paid to environmental issues and, in connection with this, to the development of hydrogen energy. In turn, this requires the large-scale production of ultra pure hydrogen. Currently, most hydrogen is obtained by converting natural gas and coal. In this regard, the issue of the deep purification of hydrogen for use in fuel cells is very relevant. The deep purification of hydrogen is also necessary for some other areas, including microelectronics. Only palladium membranes can provide the required degree of purification. In addition, the use of membrane catalysis is very relevant for the widely demanded processes of hydrogenation and dehydrogenation, for which reactors with palladium membranes are used. This process is also successfully used for the single-stage production of high-purity hydrogen. Polymeric palladium-containing membranes are also used to purify hydrogen and to remove various pollutants from water, including organochlorine products, nitrates, and a number of other substances.

For the first time, a systematic study was carried out of the replacement of the low-volatility solvents N-methyl-2-pyrrolidone (NMP) or dimethylsulfoxide (DMSO) with the high-volatility solvent acetone in the casting solution of polyacrylonitrile (PAN). The effect of acetone’s presence in the casting solution on the performance of ultrafiltration membranes fabricated via vapor-induced phase separation (VIPS) was investigated. It was possible to replace 40% of NMP and 50% of DMSO with acetone, which resulted in the reduction of the casting solution viscosity from 70.6 down to 41.3 Pa∙s (20% PAN, NMP), and from 68.3 down to 20.6 Pa∙s (20% PAN, DMSO). It was found that 20 min of exposure to water vapor (relative humidity—85%) was sufficient to govern the phase separation, which was mainly induced by the water vapor. Regardless of the casting solution composition (15 or 20% PAN; DMSO or NMP), all membranes formed via VIPS possessed a sponge-like porous structure. The addition of acetone to the casting solution allowed the reduction of the transport pore size from 35–48 down to 8.5–25.6, depending on the casting solution composition. By varying the acetone content at constant polymer concentration, it was possible to decrease the molecular weight cut-off (MWCO) from 69 to 10 kg/mol. Membranes prepared from 20% PAN solution in an acetone/DMSO mixture had the lowest MWCO of 10 kg/mol with a water permeance of 5.1 L/(m²·h·bar).

This work was focused on the mitigation of physical aging in thin-film composite (TFC) membranes (selective layer ~1 μm) based on polymer intrinsic microporosity (PTMSP) by the introduction of both soft, branched polyethyleneimine (PEI), and rigid, porous aromatic framework PAF-11, polymer additives. Self-standing mixed-matrix membranes of thicknesses in the range of 20–30 μm were also prepared with the same polymer and fillers. Based on 450 days of monitoring, it was observed that the neat PTMSP composite membrane underwent a severe decline of its gas transport properties, and the resultant CO₂ permeance was 14% (5.2 m³ (STP)/(m²·h·bar)) from the initial value measured for the freshly cast sample (75 m³ (STP)/(m²·h·bar)). The introduction of branched polyethyleneimine followed by its cross-linking allowed to us to improve the TFC performance maintaining CO₂ permeance at the level of 30% comparing with day zero. However, the best results were achieved by the combination of porous, rigid and soft, branched polymeric additives that enabled us to preserve the transport characteristics of TFC membrane as 43% (47 m³ (STP)/(m²·h·bar) after 450 days) from its initial values (110 m³ (STP)/(m²·h·bar)). Experimental data were fitted using the Kohlrausch–Williams–Watts function, and the limiting (equilibrium) values of the CO₂ and N₂ permeances of the TFC membranes were estimated. The limit value of CO₂ permeance for neat PTMSP TFC membrane was found to be 5.2 m³ (STP)/(m²·h·bar), while the value of 34 m³(STP)/(m²·h·bar) or 12,600 GPU was achieved for TFC membrane containing 4 wt% cross-linked PEI, and 30 wt% PAF-11. Based on the N₂ adsorption isotherms data, it was calculated that the reduction of the free volume was 1.5–3 times higher in neat PTMSP compared to the modified one. Bearing in mind the pronounced mitigation of physical aging by the introduction of both types of fillers, the developed high-performance membranes have great potential as support for the coating of an ultrathin, selective layer for gas separation.

A traditional technology for removing acid gases includes absorption by aqueous solutions of alkanolamines. Despite a high degree of gas flow purification and the high productivity of this process, there is a problem of thermo-oxidative degradation of the absorption solution. Degradation products are thermally stable and tend to accumulate within the system, resulting in significant operational problems. One of the promising approaches to the regeneration of alkanolamine absorbents is combining of membrane filtration and electrodialysis. This paper presents the first study of the effect of the pore size of a membrane used for prefiltration of an alkanolamine absorbent on the efficiency of the removal of heat-stable salts (HSS) by electrodialysis. Our findings indicate that both the initial HSS content and the effectiveness of their extraction vary depending on the alkanolamine type. Such variation is determined by the different mechanisms of a resin formation in absorbent solutions depending on the alkanolamine type. It was shown that decreasing the pore size and transition from microfiltration to nanofiltration enhances the degree of HSS extraction from 55 to 65% for classical electrodialysis and up to 87% for bipolar electrodialysis. To address the issue of fouling in ion-exchange membranes, a sequential washing with acid and alkaline solutions has been proposed. Our results indicate that this method makes it possible to restore the degree of HSS extraction from absorption solutions by 95%.