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This study compares pressure retarded osmosis (PRO) and the enzymatic membrane reactor (EMR) for the production of green energy in the form of power density and biomethanol, respectively. A systematic design of the biocatalytic membrane reactor and the PRO membrane system was carried out where we combined physical adsorption of polyelectrolyte (PE) and the graphene oxide (GO) layer-by-layer (LbL) assembly system. The hybrid LbL structure is proposed as a strategy to simultaneously advance the operational stability of the enzymes in the EMR and to increase hydrophilicity and power density in the PRO approach. Using polydopamine (PDA), poly(diallyldimethylammonium chloride) (PDADMAC) and GO allowed functionalization of polysulfone (PSF) membranes for subsequent Alcohol Dehydrogenase (ADH) immobilization in the EMR and functionalization of polyamide (PA) membranes for PRO. Tailoring membrane surface chemistry allowed an increase in enzyme conversion rate in comparison to the pristine, unmodified membrane (99.6% vs 2%, respectively) without significantly compromising water permeability. Moreover, power density increased from 2.10 to 2.64 W/m2 for pristine and modified membrane, respectively. Energy production in kJ/m2·h was compared and the most efficient technology was chosen.

Enzymatic membrane (EM) is a tool allowing to simultaneously upgrade enzymatic catalysis and membrane separation processes. However, their commercial use is often restricted by a trade-off between catalytic and mass transfer properties of the system. Herein, we report a new approach to the design of enzymatic membrane reactors (EMRs) - aimed to find the optimal balance between biocatalytic activity, water permeability, and enzyme loading; where we used co-deposited polyallylamine hydrochloride/polydopamine (PAH/PDA) membrane coatings as a tool to control the overall reactor performance. First, we demonstrate that tailoring the PAH/PDA coating chemistry can be more effective for promotion of total biocatalytic activity of EM with immobilized alcohol dehydrogenase (ADH) than increasing the amount of immobilized enzyme on a membrane support. Then, we show how the PAH/PDA ratio (0, 1:10, 1:2, 5:2), modification time (0.25, 1, 4, 16 h) and ionic strength (0.1–1.0 M NaCl) affect morphology of the membrane coating and alter the mechanisms of ADH-support interactions. Lastly, we illustrate the versatility of the PAH/PDA-coated membranes for application in other enzymatic systems on the example of glycerol dehydrogenase (GDH) and evaluate the performance of two EMRs as a function of applied pressure (1–3 bar). The final values of biocatalytic activities 25.4 ± 4.0 and 3.5 ± 0.3 mU/cm2 (which correspond to 140 ± 22 and 67 ± 5% immobilization efficiencies) for immobilized ADH and GDH, respectively, demonstrate that PAH/PDA-coated membranes not only can be used for simultaneous reaction and recovery of the biocatalyst, but also for enhancement of enzymatic activity - due to opportunity of reaction rate control in the membrane reactor.

ZIF-94 is a zeolitic imidazolate framework with the same SOD type topology than ZIF-8 but with an aldehyde group functionalized organic ligand. This turns ZIF-94 less thermally stable than ZIF-8 but with interesting properties of water and carbon dioxide adsorption, making the former a material highly suitable for carbon capture technologies. In this work, an alternative procedure for the synthesis of ZIF-94 was developed based on the use of NaOH as deprotonator. Besides, the crystallization was carried out in a very short time (1–20 min) at room temperature while centrifuging at 10,000 rpm. This made possible the simultaneous crystallization and separation of the product material giving rise, together with the use of the inorganic deprotonator, to a very efficient process with crystallization yields higher than 65%. For the best conditions tested (crystallization-centrifugation time of 5 min), 66 ± 24 nm in particle size, highly crystalline ZIF-94 with 485 m2 g−1 of specific surface area was obtained at a crystallization yield of 66.9%. Similar properties were obtained for ZIF-94 when prepared from recycled reagents (solvent, ligand and Zn salt).

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 CO2 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 N2 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 CO2/N2 mixture with a CO2 permeability of 157 ± 6.5 Barrer (with 67 % improvement compared to fresh pure polymer membrane with 94 ± 2 Barrer) and a CO2/N2 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.

[Background] The commercialization of thin film composite (TFC) hollow fiber (HF) membranes remains challenging owing to issues associated with membrane manufacturing., [Methods] TFC membranes were synthesized by microfluidic interfacial polymerization of polyamide (PA) on polysulfone hollow fiber (HF) membrane modules. A total of 33 HF membrane modules were prepared with different number of HFs (from 1 to 25) and different lengths (from 10 to 50 cm). They were evaluated in a nanofiltration operation in terms of water permeance and rose Bengal (RB) and MgSO4 rejections., [Significant findings] Among the 33 modules, 73% showed RB rejections higher than 95%, while 36% of the modules reached rejections above 99%. During the membrane synthesis, different parameters, such as PA monomer concentration, residence time and reaction time, were studied. As a result, the amount of monomer was reduced by ca. 80%. The versatility of microfluidics allowed incorporating hydrophilic metal-organic framework (MOF) ZIF-93 to produce HF modules with PA/MOF bilayered membranes (a continuous layer of MOF between the support and the PA film) which led to an important enhancement of the water permeance from 1.3 (bare PA membrane) to 5.3 L·m−2·h−1·bar−1 (PA/ZIF-93 HF membrane), maintaining RB rejection above 95%.

TGA curves of Sn-In-MCM-41: as synthesized, calcined, and after four catalytic cycles; XRD patterns of as-synthesized and calcined Sn-In-MCM-41; XRD patterns of as-synthesized and calcined In-MCM-41; FTIR spectra of calcined Sn-In-MCM-41, Sn-MCM-41, and In-MCM-41; FTIR spectra of Sn-In-MCM-41, Sn-MCM-41, and In-MCM-41 before and after pyridine adsorption and heating at 353 K; nitrogen adsorption–desorption isotherms of Sn-In-MCM-41, Sn-MCM-41, and In-MCM-41; BJH adsorption of Sn-In-MCM-41, Sn-MCM-41, and In-MCM-41; complete XPS spectra of Sn-In-MCM-41 fresh and after four catalytic cycles, Sn-MCM-41, and In-MCM-41; XPS spectra of Sn-MCM-41 fresh and after four catalytic cycles; catalytic results obtained for sugar conversion with Sn-In-MCM-41 in catalytic cycles (160 °C for 20 h, 160 mg of catalyst, and 225 mg of glucose); reaction mechanism; inputs for the LCA calculations on GaBi Software; flowchart for the production of 1 kg of glucose (Ecoinvent); environmental impact indicators (EIIs), units, and recommendation level; environmental impact indicator values; and contribution of the different processes to the EII values for the biochemical and chemical routes.

Global warming is considered as a consequence of extensive use of fossil fuels. Post combustion CO2 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 CO2 permeability and CO2/N2 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 CO2/CH4 separation and successfully compared in terms of improved CO2 permeability and CO2/CH4 selectivity.

Global energy demand is met in large part, by burning of fossil fuels, which is causing global warming. Mixed matrix membranes (MMMs) with metal organic frameworks (MOFs) as fillers are an interesting alternative for capturing post combustion CO2 which would make the energy sector sustainable. This research is focused on the synthesis of MOF ZIF-94 from the recycling of its mother liquors and the incorporation of synthesized MOF into a Pebax MH 1657 for MMM fabrication. The pH and the temperature of ZIF-94 synthesis are modified and monitored and this results in various nanoparticle diameters (average particle size in the range of 41 ± 8–180 ± 73 nm). Incorporation of ZIF-94 significantly improves the performance of the bare Pebax MH 1657 membrane. The maximum CO2/N2 selectivity and CO2 permeability are obtained for 10 wt% ZIF-94 loading in 9 wt% (polymer concentration in 70/30 (v/v) ethanol/water solution) Pebax MH 1657 matrix being 36 ± 7 (71% increment compared to bare membrane) and 137 ± 31 Barrer (80% improvement), respectively.

The production of MOFs at large scale in a sustainable way is key if these materials are to be exploited for their promised widespread application. Much of the published literature has focused on demonstrations of preparation routes using difficult or expensive methodologies to scale. One such MOF is nano-zeolitic imidazolate framework-8 (ZIF-8) – a material of interest for a range of possible applications. Work presented here shows how the synthesis of ZIF-8 can be tracked by a range of methods including X-ray diffraction, thermo gravimetric analysis and inelastic neutron scattering – which offer the prospect of in-line monitoring of the synthesis reaction. Herein we disclose how the production of nano-ZIF-8 can be conducted at scale using the intermediate phase ZIF-L. By understanding the economics and demonstrating the production of 1 kg of nano-ZIF-8 at pilot scale we have shown how this once difficult to make material can be produced to specification in a scalable and cost-efficient fashion.

The use of biomass for the production of energy and higher added value products is a topic of increasing interest in line with growing environmental concerns and circular economy. Mesoporous material Sn-In-MCM-41 was synthesized for the first time and used as a catalyst for the transformation of sugars to methyl lactate (ML). This catalyst was characterized in depth by various techniques and compared with Sn-MCM-41 and In-MCM-41 catalysts. In the new Sn-In-MCM-41 material, both metals, homogeneously distributed throughout the mesoporous structure of MCM-41, actuate in a cooperative way in the different steps of the reaction mechanism. As a result, yields to ML of 69.4 and 73.9% in the transformation of glucose and sucrose were respectively reached. In the case of glucose, the ML yield 1.5 and 2.6 times higher than those of Sn-MCM-41 and In-MCM-41 catalysts, respectively. The Sn-In-MCM-41 catalyst was reused in the transformation of glucose up to four cycles without significant loss of catalytic activity. Finally, life cycle assessment comparison between chemical and biochemical routes to produce ML allowed us to conclude that the use of Sn-In-MCM-41 reduces the environmental impacts compared to Sn-MCM-41. Nevertheless, to make the chemical route comparable to the biochemical one, improvements in the catalyst and ML synthesis have to be achieved.

Since carbon dioxide (CO2) 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 CO2 emissions. Among the different strategies scientists propose for CO2 reduction, direct CO2 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 CO2 separation. Finally, the process considerations for DAC using membranes are stated to guide the new researchers in the field.

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 CO2, which increases the CO2/N2 solubility selectivity (17.5 and 30.5 for Pebax® 1657 and Renew®, respectively) and hence the CO2/N2 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 CO2. 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 CO2 permeabilities of 167 and 164 Barrer and CO2/N2 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.