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• Optimization of Pebax® 3533/solvent composition for membrane application. • Porous coordination polymer MIL-178(Fe) as a filler for mixed matrix membranes. • 5 wt.% MIL-178(Fe) as mixed matrix membrane optimum loading. • Improved CO 2 permeability of 312 ± 5 Barrer with CO 2 /N 2 selectivity of 25.0 ± 0.5. Global warming is considered as a consequence of extensive use of fossil fuels. Post combustion CO 2 capture is an interesting and alternative solution where mixed matrix membranes (MMMs) can be an exciting candidate. This research focuses on the optimization of MMM composition consisting of Pebax® 3533 as the polymer matrix and porous coordination polymer (PCP) MIL-178(Fe) as a filler for gas separation application. MIL-178(Fe) characterized with SEM, TEM and TGA were applied to compare bare polymer and MMM. Optimum composition of the MMM obtained was 5 wt.% MIL-178(Fe) in Pebax® 3533. Average thickness of the optimized dense MMM was 116 ± 8 µm. Such MMM showed CO 2 permeability and CO 2 /N 2 selectivity of 312 ± 5 Barrer and 25.0 ± 0.5, respectively, 12% and 25% improved regarding the bare membrane. Additionally, optimum MMM was applied for CO 2 /CH 4 separation and successfully compared in terms of improved CO 2 permeability and CO 2 /CH 4 selectivity. [Display omitted] [ABSTRACT FROM AUTHOR]

We analyze the gas separation performance of five polyether-block-amide type copolymers (Pebax® 1657, Renew®, 2533, 3533 and 4533). These codes are composed of different hard and rubbery segments with different proportions. Dense membranes were prepared by the casting-solution method and studied by elemental, thermogravimetric and X-ray diffraction analyses, FTIR-ATR spectroscopy and single and mixed gas permeation. Codes with the best separation performance are those of polyethylene oxide as the soft phase (Pebax® 1657 and Renew®) due to the more intense interactions of this segment with CO 2 , which increases the CO 2 /N 2 solubility selectivity (17.5 and 30.5 for Pebax® 1657 and Renew®, respectively) and hence the CO 2 /N 2 separation selectivity of the membrane (36 and 37 for Pebax® 1657 and Renew®, respectively, obtained from mixed gas permeation). It is also noticeable that the proportion of the soft phase in the copolymer determines the permeability of CO 2. It was found that the codes with a greater soft/hard segment ratio (Pebax® 2533 and 3533) have also a greater permeability value (239 and 220 Barrer for Pebax® 2533 and 3533, respectively, measured by mixed gas permeation). Pebax® Renew® was the polymer with the best separation performance with CO 2 permeabilities of 167 and 164 Barrer and CO 2 /N 2 selectivities of 41 and 37, measured by single and mixed gas permeation, respectively. The comparison between the single and mixture gas permeation results revealed a relatively good correspondence between both for most of the Pebax® codes tuned by the solubility and diffusion properties of the polymers. [Display omitted] • The gas separation performance of five codes of Pebax® type copolymer was studied. • Results obtained by mixed gas and time lag experiments were compared for the CO 2 /N 2 system. • The nature and proportion of PA and PE determined the final membrane separation performance. • Apparent activation energies of permeation were calculated using both methods. [ABSTRACT FROM AUTHOR]

Thin film composite membranes of poly(ether-block-amide) copolymer Pebax® 3533 were prepared for the first time on asymmetric polysulfone supports by a phase inversion method. The casting solution concentration and the number of layers were varied to study their influence on the selective layer thickness and the gas separation performance. The casting solution concentrations of polymer dissolved in the 1-propanol/1-butanol mixture were 0.25, 0.5, 1.0 and 1.5 wt%. These conditions produced membranes with selective skin layers with thicknesses from 0.2 to 1.8 µm. All the membranes were characterized by scanning electron microscopy, thermogravimetric analysis and infrared spectroscopy. Furthermore, the intrinsic viscosity of all the casting solutions was studied to understand the effect of the polymer concentration on the homogeneity and the gas separation properties of the obtained membranes. In general, lower viscosity of casting solutions rendered to more defective skin layers, resulting in a higher number of layers required to obtain selective membranes. The gas separation performance was tested for the post-combustion 15/85 CO 2 /N 2 mixture at 25–50 °C and under a feed pressure of 3 bar. The best separation performance was achieved with the 0.5 wt% casting solution membranes after the deposition of four polymer layers, obtaining a CO 2 permeance of 127 GPU and a CO 2 /N 2 selectivity of 21.4 at 35 °C, the same selectivity of the corresponding dense membrane but with much higher permeance. [Display omitted] • Thin film Pebax®3533/PSF membranes were fabricated for the first time by a phase inversion method. • The effect of the viscosity of casting solutions on the deposition of Pebax® layer was studied. • With diluted casting solutions, a minimum of four Pebax® layers were required. • Selective skin layer thicknesses of Pebax ranged from 0.2 to 1.8 µm. • The effect of casting solution concentration and number of polymer layers on the CO 2 /N 2 separation was studied. [ABSTRACT FROM AUTHOR]

[Display omitted] • Recycling of mixed matrix membranes (MMMs) made of polymer Pebax® 1657 and MOF ZIF-94. • MMMs were dissolved and the polymer and the MOF were separately recovered. • Incorporation of recycled ZIF-94 in recycled polymer produced defect free membranes. • MMMs with a 10 wt% of ZIF-94 loading were tested for the separation of the CO 2 /N 2 mixture. • The proposed methodology was extended for recycling of ZIF-8. Mixed matrix membranes (MMMs) consisting of fillers (e.g. metal organic frameworks (MOFs)) in polymer matrix are considered as an interesting alternative for capturing post combustion CO 2 towards a sustainable development. This research is focused on the recycling of MMMs made of polymer Pebax® 1657 and MOF ZIF-94. Upon MMM preparation, characterization and testing, MMMs were dissolved to recover polymer and MOFs separately. Recovered products were characterized by SEM, EDX, FTIR, TGA, XRD, DLS, mass spectrometry and N 2 adsorption to compare their size, shape and other properties with those of fresh ones. Mean particle size of fresh and recycled ZIF-94 were 148 ± 44 nm and 164 ± 32 nm, respectively. Incorporation of recycled ZIF-94 in MMMs produced defect free membranes which was confirmed by SEM and gas separation measurements. These MMMs, with a 10 wt% ZIF-94 loading, were tested for the separation of the CO 2 /N 2 mixture with a CO 2 permeability of 157 ± 6.5 Barrer (with 67 % improvement compared to fresh pure polymer membrane with 94 ± 2 Barrer) and a CO 2 /N 2 selectivity of 27.5 ± 1.4 (5 % lower than that of the fresh MMM, 29.3 ± 1.8, but 20 % higher than the corresponding to the pure polymer membrane, 23 ± 2). Demonstrating its wide feasibility, the proposed methodology was also applicable for recycling of ZIF-8 from Pebax® 1657 based MMMs. [ABSTRACT FROM AUTHOR]

[Display omitted] • Membranes as a promising tool for CO 2 capture. • A perspective on direct air capture (DAC) from atmosphere is given. • Process considerations to make DAC feasible are addressed. • Advantages and drawbacks of membranes over other DAC technologies are provided. • An outlook of DAC using membranes is elucidated. Since carbon dioxide (CO 2) is the primary greenhouse gas emitted into the atmosphere due to human activities, strong research efforts have been developed towards capturing and decreasing its production. Unfortunately, specific processes and activities make it impossible to avoid CO 2 emissions. Among the different strategies scientists propose for CO 2 reduction, direct CO 2 capture from the atmosphere, also known as direct air capture (DAC), represents a promising alternative in which sorbents have been mainly used. Recently, gas separation membranes have also been speculated to carry out such a separation, thanks to their smaller footprint and simpler setup and operation; however, their application remains a proposition in the field. This paper gives a perspective of the ongoing research and attempts of DAC applications via membrane separation and introduces the main membrane materials and types used for CO 2 separation. Finally, the process considerations for DAC using membranes are stated to guide the new researchers in the field. [ABSTRACT FROM AUTHOR]