Monomer Phase Research Articles

A novel salt-swelling nanofiltration membranes for drinking water purification: High mineral ions passage and efficient organic removal

BackgroundMunicipal drinking water treatment demands nanofiltration (NF) membranes with high removal efficiency for organics, high passage for mineral ions, and low operating pressure. The development of innovative and loose NF membranes is imperative. MethodsA loose-network-structured NF membrane (L-NF) was synthesized through interfacial polymerization (IP) on a PES substrate by utilizing lysine (with a flexible aliphatic chain) as standalone aqueous phase monomers. The separation performance for typical organics and mineral ions in water, as well as the permeability of the membrane were investigated. Significant findingsThe lysine-based NF membranes exhibit a reversible and appropriate salt-induced swelling effect. The increased salt concentration leads to a significant enhancement of both permeate flux and salt passage, while maintaining unaffected removal efficiency for organics. The optimized membrane (L-NF3), synthesized with a 1 % (w/v) concentration of lysine, demonstrated remarkable retention (>98 %) for organics (humic acid and sodium alginate), while concurrently displaying low retention (5.22 %-16.40 %) for mineral ions (Mg2+ / Ca2+). Furthermore, the salts in the feed led to a substantial improvement in permeate flux (239.61 %-385.70 %) compared to salt-free feed. The Lys-TFC membrane showcased outstanding performance of separation, permeability, and operational stability, underscoring its significant potential in municipal drinking water purification.

Acid-resistant polyamide-sulphonamide nanofiltration membrane with positive charge for efficient removal of dyes/metal ions in acidic wastewater

The selection of separability and surface positive charge is of significant importance for treating acidic industrial wastewater with acid-resistant nanofiltration (NF) membranes. In this work, polyvinylidenefluoride (PVDF) flat membrane was used as the base membrane material, with polyethyleneimine (PEI) as the aqueous monomer and trimesoyl chloride (TMC)/benzene-1,3-disulfonyl chloride (BDSC) as the organic phase monomers, to prepare PEI-polyamide-sulphonamide (PASA) NF membrane through interfacial polymerization (IP). The influence of reaction conditions on membrane separation performance and corrosion resistance were studied, and the performance differences of the membrane under different ratios of TMC and BDSC were explored. PEI-PASA NF membrane was characterized by FTIR, XPS, SEM, contact angle tester, and mechanical strength tester. The results showed that the PEI-PASA NF membrane prepared under optimal conditions had a strong positive charge on the surface, with a water flux of 17.54 L·m−2·h−1 at 5 bar, and after static assessments in 10 % H2SO4 solution at 55 °C for 24 h, the methyl orange rejection remained kept over 95 %; after dynamic filtration in 1 % HCl for 120 h, the rejection performance of the membrane remained stable (FeCl3 96.88 %, CuCl2 93.72 %), indicating the potential application inharsh conditions, especially acid wastewater treatment.

Large-Scale, Vertically Aligned 2D Subnanochannel Arrays by a Smectic Liquid Crystal Network for High-Performance Osmotic Energy Conversion.

The osmotic energy, an abundant renewable energy source, can be directly converted to electricity by nanofluidic devices with ion-selective membranes. 2D nanochannels constructed by nanosheets possess abundant lateral interfacial ion-exchange sites and exhibit great superiority in nanofluidic devices. However, the most accessible orientation of the 2D nanochannels is parallel to the membrane surface, undoubtedly resulting in the conductivity loss. Herein, first vertically aligned 2D subnanochannel arrays self-assembled by a smectic liquid crystal (LC) network that exhibit high-performance osmotic energy conversion are demonstrated. The 2D subnanochannel arrays are fabricated by in situ photopolymerization of monomers in the LC phase. The as-prepared membrane exhibits excellent water-resistance and mechanical strength. The 2D subnanochannels with excellent cation selectivity and conductivity show high-performance osmotic energy conversion. The power density reaches up to about 22.5W m-2 with NaCl solution under a 50-fold concentration gradient, which is among with ultrahigh power density. This membrane design concept provides promising applications in osmotic energy conversion.

Gadolinium oxide Nanoparticles Infusion in Heat-Cured Acrylic Denture Base Material: Impact on Glass Transition Temperature and Mechanical Strength Enhancement

Introduction: Nano dentistry has paved the way for advanced therapeutic opportunities in various dental disciplines, particularly in the improvement of oral health. One area of focus is the enhancement of mechanical properties of dental materials, such as acrylic resins commonly used in denture base materials. Various strategies, including chemical corrections and the addition of particles, have been explored to augment the mechanical qualities. This study investigates the impact of incorporating Gadolinium oxide nanoparticles into heat-cured acrylic denture materials. Materials and Methods: The denture base was processed using a standardized approach, with the addition of Gadolinium oxide nanoparticles during the monomer phase. A total of 120 specimens were fabricated. 30 specimens for each test using 10 specimens for each nanoparticle concentration (Control 0%, 1%, and 1,5% nanoparticles). The nanoparticles were dispersed using sonication to ensure uniform distribution. The study assessed properties such as glass transition temperature using a differential scanning calorimeter, impact strength and transverse strength utilizing an Instron universal testing machine, and surface roughness via profilometer measurements. Scanning electron microscope also utilized. One way ANOVA was used to determine the mean differences. Results: The study revealed significant improvements in glass transition temperature, impact strength, and transverse strength. The peak values were often seen in the 1.5% wt. group. Surface roughness, however, showed non-significant changes with nanoparticle additions, possibly due to the minimal involvement of nanoparticles on the outer surface. Conclusion: Incorporating Gadolinium oxide nanoparticles into heat-cured acrylic denture base materials demonstrated notable enhancements in key mechanical properties. The findings suggest that nanoparticle additions contribute to increased strength and rigidity, as evidenced by improvements in impact and transverse strength. However, surface roughness remained largely unaffected. This study contributes valuable insights into the potential benefits of nanotechnology in optimizing dental materials for improved clinical performance and patient outcomes.

Advanced reverse osmosis membranes prepared by counter-diffusion of organic phase monomers induced by polypyrrole additives

Highly permeable thin film composite (TFC) reverse osmosis (RO) membranes with abundant free volume are desirable for water treatment. However, the strategy of controlling the microstructure of the separation layer with high free volume rate is still a challenge. In this work, a modified strategy for the preparation of high-performance TFC RO membrane with inverse diffusible polypyrrole nanoparticles (PPYN) as organic phase additive was developed. The combination of PPYN and trimesoyl chloride (TMC) would diffuse backwards from the organic phase into the aqueous phase during the reaction process to disrupt the normal interfacial polymerization (IP) and thus introduce more free volume in the RO membrane due to the nanobubbles from violent reactions. Moreover, the thickness of the modified membrane decreased and the hydrophilicity increased based on the modulation of IP by PPYN, which facilitated the water molecules to transport. The prepared RO-PPYN membranes showed nearly three times the flux compared with the pristine RO membrane without sacrificing separation selectivity. Furthermore, the anti-biofouling property of the modified membrane was also improved. This work successfully demonstrated the potential use of PPYN as an organic filler to enhance the performance of seawater desalination in RO membranes. Our modification strategy provides an efficient and convenient way to prepare novel RO membranes with high permeability.

Impact of Conditions of Methyl Methacrylate Suspension Polymerization on the Particle Size Distribution of the Polymer

The impact of operational conditions for carrying out methyl methacrylate suspension polymerization during stabilization of the system with dispersants of different chemical natures: poly-2-acrylamido-2-methylpropanesulfonic acid and Mg(OH)2, was studied. The role of the contribution of the chemical nature of the dispersant, which reduces the interfacial tension between the monomer and aqueous phases, to the particle size distribution of the polymer particles is shown. When polymerizing methyl methacrylate in the presence of water-insoluble Mg(OH)2, the interfacial tension diminishes, which brings about the formation of a highly dispersed polymer without the use of high-speed dispersion of the reaction mass.

Polyurea nanofiltration membranes with extreme-pH stability and high separation performance

Development of high-performance nanofiltration membranes with extreme-pH stability is an urgent need for treatment of wastewater from metallurgical and paper industries. In this study, we design a kind of oil phase monomer toluene diisocyanate (TDI) and the aqueous phase monomer polyethyleneimine (PEI) to prepare polyurea nanofiltration membranes. The special bonding type and dense crosslinking structure of polyurea were used to resist the attack of extreme pH conditions. The support-free interface polymerization was employed to minimize the membrane thickness. The TDI-PEI10000 composite membranes achieved rejection of 97.5% for MgCl2, with a corresponding pure water permeance of 20.0 L m-2 h-1 bar-1. After exposure to H2SO4 solution with pH=1 for 440 h or NaOH solution with pH=13 for 200 h, the MgCl2 rejection remained above 90%. Our study provides a facile approach to constructing extreme pH-stable separation membranes.

Preparation and performance of thin film composite solvent nanofiltration membrane based on fluorinated diamine monomers

The high perm-selectivity and long-term solvent resistance of organic solvent nanofiltration (OSN) membranes in various solvents pose significant challenges for their development. In this study, ultra-low content mixture of fluorinated diamine (5-trifluoromethyl-1,3-phenylenediamine or 4-trifluoromethyl-1,2-phenylenediamine) and m-phenylenediamine (MPD) as aqueous phase monomers and ultra-low content trimesoyl chloride (TMC) in n-hexane as organic phase monomer were used to perform interfacial polymerization (IP), then followed by crosslinking and solvent activation. By this way, two kinds of ultra-thin and ultra-smooth fluorinated polyamide OSN membranes were achieved. Under optimized conditions, these two kinds of OSN membranes, TFC-5F2,II and TFC-4F1,II, have surface roughness of 2.5 and 3.0 nm, respectively. They show ethanol permeance of 73.9 and 60.9 L m−2 h−1 MPa−1, and RDB rejection of 98.5% and 99.2%, respectively, using 100 mg L−1 rhodamine B / ethanol solution as feed. They show ethyl acetate permeance of 209.4 and 117.0 L m−2 h−1 MPa−1, respectively, and catalyst rejection of 98.2% and 98.8%, respectively, using 50 mg L−1 Jacobsen catalyst/ethyl acetate solution as feed. Meanwhile, they have pure n-hexane permeance of 32.5 and 36.8 L m−2 h−1 MPa−1, respectively. Moreover, they show excellent stability in highly polar solvents, thus have good application prospects in the separation and purification of various organic solvent systems.

Enhanced desalination performance and arsenate removal using semi‐aromatic polyamide‐based pervaporation membranes by modifying with amino‐acids via interfacial polymerization

AbstractIn this study, the semi‐aromatic polyamide membranes were synthesized by the interfacial polymerization between piperazine (PIP) monomers in the water phase and Benzene‐1,3,5‐tricarbonyl chloride in the organic phase. To further modify the semi‐aromatic pervaporation membrane, the two amino acids, glycine, and l‐lysine, were mixed with PIP monomers for interfacial polymerization. The morphology and physicochemical properties of the synthesized membranes were analyzed using Fourier transform infrared (FTIR), field emission scanning electron microscope (FE‐SEM), atomic force microscope (AFM), and contact angle measurements. The results show that the semi‐aromatic polyamide membranes modified by the two amino acids possess a higher hydrophilic surface and lower thickness compared to the unmodified membrane. Additionally, the permeation flux of the semi‐aromatic polyamide membranes was improved by 18.6% and 38.5% as modified with glycine and l‐lysine, respectively, at the operating temperature of 70°C when the rejection of both NaCl and arsenic are higher than 99.8%. Furthermore, the operating temperature significantly influenced the permeation flux, while the salt rejections were insignificantly affected. The permeation flux increases by 3.2‐ and 4.0‐folds for glycine and lysine‐modified membranes, respectively, when elevating the feed temperature from 40°C to 70°C. The highest permeation flux of 29.5 kg m−2 h−1 with a 5 wt% NaCl rejection of 99.8% was obtained at 70°C by using 0.3 wt% l‐lysine modified polyamide (PA) membrane. For elimination of 1.5 mg L−1 As solution at the feed temperature of 70°C, such l‐lysine modified PA membrane exhibited the permeation flux of 30.5 kg m−2 h−1 and As rejection of 99.6%, respectively. This work provides a cost‐saving, facile, and eco‐friendly preparation method for effectively improving the permeation flux while not sacrificing the high rejection of salts of the modified membranes.

Enhanced pervaporation dehydration performance of polyamide thin‐film composite membrane with sodium alginate hydrophilic surface modification

AbstractBased on the solution‐diffusion model of pervaporation (PV) technique, the development of thin‐film composite membranes (TFC) with a highly hydrophilic surface and hydrophobic internal structure is more conducive to the rapid adsorption and desorption of water molecules to overcome the trade‐off effect between flux and separation selectivity. Herein, the polyamide PV membrane was fabricated via interfacial polymerization (IP) with trimesoyl chloride (TMC) and polyethylenimine (PEI) as organic and aqueous phase monomer, respectively, on the hydrolyzed polyacrylonitrile (HPAN) substrate. Subsequently, the hydrophilic modification layer was prepared via sodium alginate (SA) crosslinking with Ca2+ to form the egg‐box network. The results indicated the optimized TFC membrane exhibited high separation factor of 525.1 with desirable permeation flux of 2083.9 g m−2 h−1 for the pervaporation dehydration 85 wt% ethanol/water solution at 70°C. The modification method of hydrophilic surface opens up new avenues for the preparation of PV membrane with high separation performance and low‐cost.

A novel loose nanofiltration membrane with high permeance and anti-fouling performance based on aqueous monomer piperazine-2-carboxylic acid for efficient dye/salt separation

Dye effluent is regarded as one of the most hazardous industrial effluents. Although loose nanofiltration (NF) membranes have been considered as an effective alternative technique for treating dye effluent, their development is still constrained by subpar permeance, separation efficiency and anti-fouling performance. In this work, a novel loose polyamide (PA) NF membrane was designed employing a conventional interfacial polymerization process using piperazine-2-carboxylic acid (PIP-COOH) and trimesoyl chloride as aqueous and organic phase monomers, respectively. The presence of unique electron-absorbing carboxyl groups on the PIP-COOH monomer not only provided abundant negative charge on the membrane surface, but also greatly reduced the reactivity, diffusion rate and solubility in n-hexane of the aqueous monomer, allowing for the formation of a more relaxed and smoother active layer. The balanced combination of pore size screening and Donnan effect achieved precise separations with high permeability. Moreover, the interaction of the carboxyl groups with the backbone structure increased the free volume of the PA layer and improved permeability significantly. The PIP-COOH/TMC membrane prepared under the optimal conditions exhibited high water permeance of 598.1 L·m−2·h−1·MPa−1, high reactive red rejection (99.3%) and low NaCl rejection (5.4%). Furthermore, the membrane possessed exceptional anti-fouling performance thanks to the ultra-smooth surface with crucial antifouling index flux recovery ratio as high as about 99%, which showed unexpected application possibilities. In conclusion, this study offers a potential novel membrane material for the development and application of loose NF membranes in the treatment of colored effluent.

Magnetic open porous microspheres via high internal phase emulsion templating as efficient Pb adsorption material

Emulsion templating enables the synthesis of hierarchically porous polymers. By adding another phase to this process and therefore, creating a multiple emulsion templating method, it is possible to synthesise hierarchically porous microspheres. In this study water-in-oil-in-water double emulsion templating was used to prepare porous microspheres by utilising thiol-ene click chemistry. For this trimethylolpropane tris(3-mercaptopropionate) and trimethylolpropane triacrylate were used. To the monomer phase magnetic nanoparticles were added to synthesise polyHIPE microspheres with magnetic properties. The higher magnetic nanoparticles (MNPs) content also affected the morphology and microsphere size. With increasing MNPs content the bead diameter decreased, while the diameter of the primary pores of the cross-section increased. However, while the MNPs influenced the morphology, the chemical composition was not influenced. The microspheres were used for the removal of Pb2+. From a 2.9 mg/L solution up to 97.0% of Pb was removed after 24 h.

Polyphenol modification of graphene-stabilized emulsions to form electrically conductive polymer spheres

HypothesisPolyphenols, specifically tannic acid, should increase the hydrophilicity of graphene when added during the interfacial exfoliation through π-π stacking. Following Bancroft’s rule, increasing the hydrophilicity of graphene will result in a phase inversion of water-in-oil emulsions stabilized by graphene. Polymerization of the oil phase will then lead to graphene-coated spheres rather than graphene-stabilized polyHIPEs. ExperimentsOptical particle sizing, microscopy, contact angle, and electrical conductivity measurements were performed to determine the mechanism of sphere formation in graphene-stabilized emulsions modified with tannic acid. Studies focused on the effect of graphite flake size, graphite concentration, tannic acid concentration, and oil phase composition. Particle sizing and scanning electron microscopy examined the spheres' size, shape, and surface morphology. Contact angle measurements gave insight into the change in graphene surface energy. Conductivity studies examined the graphene shell surrounding the spheres. FindingsAdding tannic acid to graphene-stabilized emulsions induced a phase change from water-in-oil to oil-in-water. Contact angle measurements confirmed greater hydrophilicity of graphene in the presence of tannic acid. However, very high tannic acid concentrations led to a decrease in the stability of the emulsion. Varying the graphite flake size and concentration resulted in morphology and conductivity changes. Dilution of the monomer phase produced hollow microcapsules.

Oleo-sheets and omni-sheets: Fabric-like superabsorbers for oil, water, or any solvent

Materials that can selectively absorb oil from water could be used to clear oil spills, but such absorbents are typically either in the form of powders or small, bulky solids. In homes and labs, spills of oil are absorbed with cloth or paper towels, which are flexible and foldable, but exhibit poor absorbency. There is hence a need for fabric-like sheets that can absorb considerable oil, and here, we report the synthesis of such oleo-sheets by templating organofoams. A foam of CO2 bubbles in a water-in-oil emulsion is first created, with the bubbles stabilized by a silicone surfactant. Monomers in the oil phase (alkyl and urethane acrylates) are then polymerized rapidly at room temperature to give a porous gel. By ambient drying this gel, we make oleo-sheets (∼10 × 7 × 0.4 cm in size) and oleo-sponges (size ∼2 × 2 × 1 cm), which are both soft, pliable materials with interconnected pores. These materials are hydrophobic (water contact angle ∼130°) and they selectively absorb a range of oils (organic solvents) from water. Their absorption capacity (> 50 g/g) exceeds that of commercial absorbents like polyurethane sponges or cloth pads. We also make a magnetic oleo-sponge – after such a sponge absorbs oil, it can be lifted up by a magnet. Lastly, we create an omni-sheet with two distinct sides, one that selectively absorbs oil while the other does the same for water. Thus, the omni-sheet can pick up any spilled liquid. The materials reported here are likely to find application in cleaning up spills due to their unique combination of convenient form factor, robust mechanical properties, and excellent absorbency. Moreover, our synthesis technique can be easily scaled up as it is simple and energy-efficient (since it does not involve freeze-drying) and environment-friendly.

Highly selective and permeable β-cyclodextrin based polyester nanofiltration membranes maintaining good chlorine resistance

Possessing high chlorine resistance is an important consideration for membranes to be applied for water treatment. In this study, the superior chlorine resistant β-cyclodextrin (β-CD) based polyester membranes were developed via interfacial polymerization (IP) with the β-CD and glycerol or mannitol as the aqueous phase monomers. By adjusting the compositions of the aqueous phase, the pore size and distribution of the resultant membranes were accurately controlled, thus improving the separation efficiency of the membranes. The optimized membrane (β-CD/Ma3) had the higher water flux (60.4 L‧m-2‧h-1 at 2.0 bar) and Na2SO4 retention (95.6%). After immersed in 10 ppm sodium hypochlorite (NaClO) solution for 360 h, the membrane performance in terms of water flux and salt retention was almost unaltered, mirroring a good long-term stability. In another test, the Na2SO4 retention of membrane remained at 91.7%, which was only 4.1% lower than the original value, after exposure to a high concentrated NaClO solution (2000 ppm) for 72 h. Fouling cycling test was also performed, and the flux was maintained as high as 97.2% of the original value after examination of three cycles. All these observations clearly indicate that the optimized membrane has outstanding chlorine resistance and superior antifouling property.

Incorporating functionalized acyl chloride monomer with rigid pyrrolidinyl group via two-step interfacial polymerization for improving permeability of reverse osmosis membranes

Novel acyl chloride monomer 5-(1-pyrrolidinyl)-1,3-benzenedicarbonyl dichloride (PIPC) featuring a rigid pyrrolidinyl group was proposed as an organic phase monomer to fabricate reverse osmosis (RO) membranes possessing exceptional water permeability and NaCl rejection via a two-step interfacial polymerization method. First, m-phenylenediamine (MPD) in the aqueous phase solution polymerized with PIPC in the first organic phase solution to form the much looser polyamide. After that the remaining MPD continued to diffuse to polymerize with trimesoyl chloride in the second organic phase solution to form the denser polyamide. The pyrrolidinyl group had steric hindrance effects and formed hydrogen bond with MPD, leading to decreasing the thickness significantly and increasing surface roughness of the separating layer. When the PIPC amount was 0.08 wt%, the PIPC-based RO membrane displayed optimal permselectivity with water flux increasing by 84.20 % compared to the original RO membrane (from 20.38 L·m−2·h−1 to 37.54 L·m−2·h−1) whereas retaining high NaCl rejection with 98.59 %. The PIPC-based RO membrane exhibited steady water flux and NaCl rejection within 120 h of filtration, as well as improved antifouling performance. Thus, preparation of the highly permeable RO membrane could be rationally achieved by the novel acyl chloride monomer with a rigid pyrrolidinyl group.

Tailor-made highly negatively charged nanofiltration membrane prepared by polyphenol derivatives for anionic dye/salt separation

Nanofiltration (NF) techniques are becoming increasingly advantageous for treating salt-containing dye wastewater. A novel NF membrane was successfully fabricated using grape seed oligomeric proanthocyanidins (OPC) as aqueous phase monomer by interfacial polymerization with isophorone diisocyanate (IPDI). The membrane surface exhibited an extremely high negative zeta potential. The experimental results showed that the negatively charged OPC/IPDI nanofiltration membranes could effectively remove anionic dyes and exhibited high NaCl/dye selectivity. Specifically, the optimal OPC/IPDI membrane exhibited a rejection of 99.4 % against Reactive Red 195 with a high permeance of 67.9 L m−2 h−1 bar−1 and a desirable NaCl/RR 195 selectivity factor of 85.3. In addition, the smooth and hydrophilic surface endowed the membranes with a desirable antifouling property. The optimized membrane achieved high flux recovery ratio values of 89.1 %, 85.5 %, and 24.75 % for the foulants of Reactive Red 195, humic acid, and bovine serum albumin, respectively. A 50-hour investigation of continuous cross-flow filtration processes showed the outstanding separation stability of the membranes. Furthermore, the membranes exhibited excellent anti-bacterial activity. Integrating all the findings, the strategy proposed in this paper for the use of polyphenol derivatives to prepare highly negatively charged membranes for the removal of anionic pollutants from saline wastewater is feasible.

Regulation of dopamine forward osmosis membrane via inorganic salt and macro-porous substrates for pharmaceutical concentration

Dopamine (DA) with good designability could self-polymerize into polydopamine (PDA) with various polymerization states in alkaline solution. However, the poor structural controllability of PDA leads to serious PDA hyper-polymers, making DA difficulty to be used as sole aqueous phase monomer during conventional interfacial polymerization (IP) for membrane preparation. In this work, the organic solvent forward osmosis (OSFO) membranes were fabricated via substrate-floating interfacial polymerization (SFIP) method with DA as sole aqueous phase monomer and macro-porous polyether sulfone (PES) membrane with pore size of 0.1–0.22 μm as substrates. Inorganic salt such as NaCl was employed as aqueous phase additive, which not only effectively regulated the oligomeric polymerization state of PDA but also promoted DA diffusion. The macro-porous substrate could enlarge the reaction contact area and relieve the internal concentration polarization in support layer. The resulting OSFO membranes exhibited an excellent ethanol flux of ∼10.70 L m−2 h−1 and lower reverse LiCl flux of ∼0.53 g m−2 h−1, as well as a high tetracycline concentration efficiency of >15 % for 1 h run whatever the tetracycline concentration in the feed (500–2000 mg/L). This work provides new insights into the fabrication of high-performance OSFO membrane for solvent recovery and pharmaceutical concentration.

Controlling polyHIPE Surface Properties by Tuning the Hydrophobicity of MOF Particles Stabilizing a Pickering Emulsion.

Metal-organic frameworks (MOFs) show promise for the capture of greenhouse gases. To be used at a large scale in fixed-bed processes, their shaping under a hierarchical structure is mandatory and remains a major challenge, while keeping available their high specific surface area. For that purpose, we propose herein an original method based on the stabilization of a paraffin-in-water Pickering emulsion by a fluorinated Zr MOF (UiO-66(F4)) with polyHIPEs (polymers from high internal phase emulsions) strategy consisting of the polymerization of monomers in the external phase. After polymerization of the continuous phase and elimination of the paraffin, a hierarchically structured monolith is obtained with the UiO-66(F4) particles embedded in the polymer wall and covering the internal porosity. To avoid the pore blocking induced by the embedment of the MOF particles, our strategy was to modify their hydrophilic/hydrophobic balance with a controlled adsorption of hydrophobic molecules (perfluorooctanoic acid, PFOA) on the UiO-66(F4) particles. This will induce a displacement of the MOF position at the paraffin-water interface in the emulsion and then make the particles less embedded into the polymer wall. This leads to the formation of hierarchically structured monoliths integrating UiO-66(F4) particles with higher accessibility, maintaining their original properties and allowing their application in fixed-bed processes. This strategy was demonstrated by N2 and CO2 capture, and we believe that such original strategy could be applied to other MOF materials.

Thin film composite membranes prepared from diaminoguanidine hydrochloride for Mg2+/Li+ separation

This study aims to prepare and investigate thin film composite (TFC) membranes with a highly positively charged rejection layer for effective separation of Mg2+/Li+. The aqueous phase monomer employed in fabricating the TFC membranes was a highly ionic and hydrophilic guanidinium, namely 1,3-diaminoguanidine hydrochloride (DAGH), using an interfacial polymerization method. Two methods were used to prepare the TFC membranes: conventional interfacial polymerization and support-free interfacial polymerization. The surface properties and morphologies of the TFC membranes were characterized by FESEM, AFM, surface zeta-potential, and water contact angle. The XPS was used to analyze the crosslinking structure of the interfacial layer. The study results revealed that the SF-TFC membrane had a higher crosslinking density and zeta-potential compared to the C-TFC membrane. Notably, SF-TFC exhibited a MgCl2 rejection of 95.09% at 7 bar, and for Mg2+/Li+ separation, the SF-TFC membrane had a Li+/Mg2+ separation factor of 23.32 at the Mg2+/Li+ mass ratio of 10. Additionally, the strong ionic and hydrophilic properties of DAGH led to the proposal of an aqueous-phase polymerization mechanism, substantiated by AFM and ESI-MS analysis.