A greener route to prepare PEBAX®1074 membranes for gas separation processes

Publisher Copyright: © 2023 The AuthorsThe solvent used in membrane fabrication is crucial for a potential industrial application, with a direct effect on its safety, environmental and economic impact. Thus, in the last years, the search for greener and safer solvents became of utmost importance aiming for a sustainable fabrication of highly performing membranes, since that also affects the final membrane morphology. Typically, solvent evaporation-based methods are used for the preparation of membranes for gas separation processes, such as dip-coating and spray coating methods. The advantage of this approach relies on the possibility of using greener non-toxic solvents, such as water and ethanol. However, an alternative route might involve the use of phase inversion methods. In this procedure, the selection of the solvent will play an even more important role, with an impact on the gas separation membrane properties. Small defects or structural changes will decisively alter the final membrane performance. In this work, it is presented for the first time the alternative use of a non-toxic and eco-friendly solvent, Rhodiasolv®Polarclean, for the preparation of CO2-selective PEBAX®-based membranes using a hybrid phase inversion method. This preliminary study evaluates the relationship between the fabrication protocol, with the resulting structural, thermal, and mechanical membrane properties for self-standing membranes. The gas separation performance was tested for different gases: H2, N2, O2, CO2 and CH4. This analysis also includes a comparison with the commonly used, although strongly restricted and hazardous, solvent N-Methyl-2-Pyrrolidone (NMP).publishersversionpublishe

Pervaporation of the low ethanol content extracting stream generated from the dealcoholization of red wine by membrane osmotic distillation

This paper presents as main contribution the combination of membrane osmotic distillation (OD) to dealcoholize red wine with hydrophobic-hydrophilic pervaporation (PV) carried out to add value to the wastewater (extracting water) produced in OD, recycling water and generating bioethanol. Membrane OD with a commercial polypropylene hollow fiber module was applied to partially dealcoholize red wine from 14.0 to 11.0 v/v% ethanol. The OD extracting water, containing only ca. 5.3 wt% ethanol, was treated by sequential PV with both hydrophobic (PDMS or zeolite silicalite-1) and hydrophilic (zeolites mordenite or faujasite) membranes. This hydrophobic-hydrophilic PV produced two main products: bioethanol (recovering 88% of the ethanol removed from the wine) and a 99.4 wt% water-rich product. This water-rich product, with a very low ethanol content, was used as extracting water in the OD, giving rise to an analogous partially dealcoholized wine, in terms of aroma contents (as determined by gas chromatography for 25 compounds), to that achieved when using fresh water

Antibacterial properties of photochemically prepared AgTiO2 membranes

Biofouling reduces the membrane performance and has become a problem in many applications. One of the strategies to reduce biofouling is to apply antibacterial materials to the membrane surface, which prevents the attachment and growth of microorganisms. In this study, the surface of flat ceramic supports was covered with TiO2 powder, and silver was applied by photoreduction using a CH3COOAg solution at room temperature. After the photoreduction, AgOx and metallic silver were found on the TiO2 as analyzed by XPS. While a negligible amount of silver was released from the prepared AgTiO2 membranes into water, the dissolution of silver was enhanced in a 0.09 M NaCl solution. The AgTiO2 membranes inhibited the growth of Escherichia coli in dark conditions. The inhibition cannot be explained only by the concentration of silver ions released from the membranes. Microscopic observation showed that direct contact with AgTiO2 kills E. coli. The results showed the possibility of improving the antibacterial activity of membranes by applying an AgTiO2 coating

Influence of Salts on the Photocatalytic Degradation of Formic Acid in Wastewater

Conventional wastewater treatment technologies have difficulties in feasibly removing persistent organics. The photocatalytic oxidation of these contaminants offers an economical and environmentally friendly solution. In this study, TiO2 membranes and Ag/TiO2 membranes were prepared and used for the decomposition of dissolved formic acid in wastewater. The photochemical deposition of silver on a TiO2 membrane improved the decomposition rate. The rate doubled by depositing ca. 2.5 mg of Ag per 1 g of TiO2. The influence of salinity on formic acid decomposition was studied. The presence of inorganic salts reduced the treatment performance of the TiO2 membranes to half. Ag/TiO2 membranes had a larger reduction of ca. 40%. The performance was recovered by washing the membranes with water. The anion adsorption on the membrane surface likely caused the performance reduction

TiO2-zeolite metal composites for photocatalytic degradation of organic pollutants in water

Immobilization of photocatalysts in porous materials is an approach to significantly minimize the hazards of manipulation and recovery of nanoparticles. Inorganic materials, such as zeolites, are proposed as promising materials for photocatalyst immobilization mainly due to their photochemical stability. In this work, a green synthesis method is proposed to combine TiO2-based photocatalysts with commercial ZY zeolite. Moreover, a preliminary analysis of their performance as photocatalysts for the abatement of organic pollutants in waters was performed. Our results show that the physical mixture of TiO2 and zeolite maintains photocatalytic activity. Meanwhile, composites fabricated by doping TiO2-zeolite Y materials with silver and palladium nanoparticles do not contribute to improving the photocatalytic activity beyond that of TiO2.This work was supported by JST SICORP Grant Number JPMJSC18C5 (Japan), the grant number PCI2018-092929 funded by MCIN/ AEI/10.13039/501100011033/ (Spain), and the National Centre for Research and Development (NCBiR, Poland) agreement number EIG CONCERT-JAPAN/1/2019

Performance of TiO2-based tubular membranes in the photocatalytic degradation of organic compounds

This work presents the photocatalytic degradation of organic pollutants in water with TiO2 and TiO2/Ag membranes prepared by immobilising photocatalysts on ceramic porous tubular supports. The permeation capacity of TiO2 and TiO2/Ag membranes was checked before the photocatalytic application, showing high water fluxes (-758 and 690 L m-2 h-1 bar-1, respectively) and <2% rejection against the model pollutants sodium dodecylbenzene sulfonate (DBS) and dichloroacetic acid (DCA). When the membranes were submerged in the aqueous solutions and irradiated with UV-A LEDs, the photocatalytic performance factors for the degradation of DCA were similar to those obtained with suspended TiO2 particles (1.1-fold and 1.2-fold increase, respectively). However, when the aqueous solution permeated through the pores of the photocatalytic membrane, the performance factors and kinetics were two-fold higher than for the submerged membranes, mostly due to the enhanced contact between the pollutants and the membranes photocatalytic sites where reactive species were generated. These results confirm the advantages of working in a flow-through mode with submerged photocatalytic membranes for the treatment of water polluted with persistent organic molecules, thanks to the reduction in the mass transfer limitations.This work was supported by JST SICORP Grant Number JPMJSC18C5 (Japan) and the grant number PCI2018-092929 funded by MCIN/ AEI/10.13039/501100011033/ (Spain) as part of the project X-MEM within the framework of the EIG CONCERT-Japan 5th Joint Call “Functional Porous Materials”

Impact of Ionic Liquid Structure and Loading on Gas Sorption and Permeation for ZIF-8-Based Composites and Mixed Matrix Membranes

Carbon dioxide (CO2) capture has become of great importance for industrial processes due to the adverse environmental effects of gas emissions. Mixed matrix membranes (MMMs) have been studied as an alternative to traditional technologies, especially due to their potential to overcome the practical limitations of conventional polymeric and inorganic membranes. In this work, the effect of using different ionic liquids (ILs) with the stable metal–organic framework (MOF) ZIF-8 was evaluated. Several IL@ZIF-8 composites and IL@ZIF-8 MMMs were prepared to improve the selective CO2 sorption and permeation over other gases such as methane (CH4) and nitrogen (N2). Different ILs and two distinct loadings were prepared to study not only the effect of IL concentration, but also the impact of the IL structure and affinity towards a specific gas mixture separation. Single gas sorption studies showed an improvement in CO2/CH4 and CO2/N2 selectivities, compared with the ones for the pristine ZIF-8, increasing with IL loading. In addition, the prepared IL@ZIF-8 MMMs showed improved CO2 selective behavior and mechanical strength with respect to ZIF-8 MMMs, with a strong dependence on the intrinsic IL CO2 selectivity. Therefore, the selection of high affinity ILs can lead to the improvement of CO2 selective separation for IL@ZIF-8 MMMsinfo:eu-repo/semantics/publishedVersio

Impact of Ionic Liquid Structure and Loading on Gas Sorption and Permeation for ZIF-8-Based Composites and Mixed Matrix Membranes

CEECIND/ 00793/2018 LA/P/0008/2020 PTDC/CTM-TM/30326/2017Carbon dioxide (CO2) capture has become of great importance for industrial processes due to the adverse environmental effects of gas emissions. Mixed matrix membranes (MMMs) have been studied as an alternative to traditional technologies, especially due to their potential to overcome the practical limitations of conventional polymeric and inorganic membranes. In this work, the effect of using different ionic liquids (ILs) with the stable metal–organic framework (MOF) ZIF-8 was evaluated. Several IL@ZIF-8 composites and IL@ZIF-8 MMMs were prepared to improve the selective CO2 sorption and permeation over other gases such as methane (CH4) and nitrogen (N2). Different ILs and two distinct loadings were prepared to study not only the effect of IL concentration, but also the impact of the IL structure and affinity towards a specific gas mixture separation. Single gas sorption studies showed an improvement in CO2 /CH4 and CO2 /N2 selectivities, compared with the ones for the pristine ZIF-8, increasing with IL loading. In addition, the prepared IL@ZIF-8 MMMs showed improved CO2 selective behavior and mechanical strength with respect to ZIF-8 MMMs, with a strong dependence on the intrinsic IL CO2 selectivity. Therefore, the selection of high affinity ILs can lead to the improvement of CO2 selective separation for IL@ZIF-8 MMMs.publishersversionpublishe

Conceptual Process Design and Simulation of Membrane Systems for Integrated Natural Gas Dehydration and Sweetening

Subsea natural gas processing attracts increased interest due to the smaller environmental footprint. Natural gas (NG) dehydration and sweetening are the main processing steps to avoid pipeline plugging and corrosion caused by the presence of water and CO2. Triethylene glycol (TEG) and amine absorption are the commercial technologies for these applications. However, membrane technology is considered as promising solutions for alternative subsea gas processing technologies, which provides unmanned operations without the requirements for rapidly periodical maintenance. In this work, a hybrid membrane process was designed for integrated dehydration and sweetening of a saturated natural gas containing 10 mol% CO2, and the process operating parameters such as inter-stage feed and permeate pressures are investigated. The simulation results indicated that the optimal permeate pressure in the 2nd -stage unit is 4 bar, and the optimal 3rd-stage feed and permeate pressures are15bar and 2 bar, respectively. The minimum specific cost of 95 mol%) for enhanced gas recovery. However, due to the relatively low water selectivity of the dehydration membranes at high pressure of 60 bar used in the simulation, the hydrocarbon loss is still quite higher. Thus, advanced membranes with high H2O/CH4 selectivity at high pressure should be pursued to promote the application of the designed membrane system for subsea natural gas dehydration and sweetening