Search

Based 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. [ABSTRACT FROM AUTHOR]

Nanofiltration (NF) membrane is of great significance for desalination of light brine and purification of drinking water. Although the development of novel preparation methods and membrane materials has improved the separation performance, it is still a major challenge to promote NF membrane toward industrial production with simpler and more controllable process. Herein, the polyphenol intermediate layer was designed by 5,5′,6,6′-tetrahydroxy-3,3,3′,3′-tetramethyl-1,1′-spirobisindane (TTSBI) with twist structure and polyethyleneimine (PEI) co-deposition to increase the surface hydrophilicity and electropositivity of the polysulfone ultrafiltration substrate. Subsequently interfacial polymerization (IP) was carried out on the polyphenol intermediate layer to assemble a polyamide ultrathin selective layer using trimesoyl chloride and piperazine monomer. Through adjusting the co-deposition time of TTSB and PEI, a unique nano-pleated structure was successfully formed on the thin-film composite membrane surface. The water permeance of the membrane was determined as 23.7 L m−2 h−1 bar−1 with 99.4% Na 2 SO 4 rejection, which was almost triple fold of the flux of the controller membrane without the intermediate layer. Our results provide an efficient and convenient way to fabricate the advanced NF membrane with higher divalent/monovalent ion selectivity and water permeance simultaneously, which will provide advices for the gas separation and pervaporation membranes with the IP method. • Novel TTSBI-PEI interlayer-based polyamide membrane was fabricated by interfacial polymerization. • The nano-pleated structure on the selective layer improved the water flux without deterioration of Na 2 SO 4 rejection. • The novel nanofiltration membrane exhibited excellent long-term stability. [ABSTRACT FROM AUTHOR]

• Novel TFC membrane was designed for pervaporation dehydration. • Separation layer with descending crosslinking degree formed with LBL assembled IP. • Ten folds increase of separation factor was achieved with the TFC membrane. • TFC membranes showed high separation performance and good stability. Thin-film composite (TFC) pervaporation membranes is of widespread interest for the alcohol dehydration, since the thin selective layer allows a high permeation flux. However, how to obtain the desired flux and separation selectivity simultaneously is still the bottleneck of industrial application with pervaporation technology. In this study, a novel ultrathin multi-layer polyurea or polyamide pervaporation membrane was designed and assembled via layer-by-layer (LBL) interfacial polymerization (IP) method on the hydrolyzed polyacrylonitrile (HPAN) substrate membrane. During the LBL assembly process, the controllable crosslinking degree of the separation layer formed through changing the concentration of the oil phase monomer while remaining the concentration of the aqueous phase monomer constant based on the solution-diffusion mechanism of pervaporation separation process. The surface characterization revealed that the tris(2-aminoethyl) amine (TAEA) 1.5 -toluene 2,4-diisocyanate (TDI) 1-0.5-0 /HPAN composite membrane exhibited much rougher surface than that of the membranes with the same crosslinking degree. The optimized composite membrane exhibited a high separation factor of 844.6 with a desirable permeation flux of 1284.3 g·m−2·h−1 for the pervaporation dehydration 95 wt% ethanol aqueous solution at 80 °C, which was 10-fold increase of separation factor compared with the control membrane. Moreover, the excellent operation stability of the TFC membrane demonstrated the promising prospect for the alcohol dehydration separation. This preparation methodology has potential application in other membrane separation process on the basis of solution-diffusion mechanism, such as gas separation and reverse osmosis membrane. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel polyamide loose NF membrane was prepared from aqueous monomer (piperazine-2-carboxylic acid). • The loose NF membrane formation mechanism was clarified. • The loose NF membrane exhibited high water permeance and outstanding separation selectivity of dye/salt. • The loose NF membrane demonstrated excellent antifouling performance. 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. [ABSTRACT FROM AUTHOR]

• Novel aliphatic acid chloride monomers were designed and synthesized. • The mean effective pore size of the BTC and HTeC membranes were 0.184 nm and 0.197 nm, respectively. • The aliphatic polyamide membrane showed more than 98% rejection rate for CaCl 2 , MgCl 2 , and MgSO 4. • The ion selectivity of Na+/Mg2+ and Na+/Ca2+ of the BTC membrane was as high as 126 and 31.5, respectively. • Antifouling properties of the fabricated membranes were also enhanced. Monomer design and reconstruction is typically a preferred route to tune the inner structure and screen the performance of polyamide nanofilms for their efficiency and ease of scaling up in industrial production. Herein, two kinds of novel acyl chloride monomers, 1,2,3,4-cyclobutane tetracarboxylic acid chloride (BTC) and 1,2,4,5-cyclohexanetetracarboxylic acid chloride (HTeC), have been designed and synthesized. The BTC and HTeC monomers can rapidly react with amine molecule at interface to form an aliphatic polyamide nanofilm that is denser than that of TMC based polyamide membrane. The resulting mean effective pore size of the BTC and HTeC polyamide nanofilms is 0.184 nm and 0.197 nm, which is lower than that of the TMC nanofilm at 0.238 nm. Desalination experiments revealed that the aliphatic polyamide membrane shows more than a 98% rejection rate for CaCl 2 , MgCl 2 , and MgSO 4 and a water flux of 84.4 kg m−2 h−1 MPa−1 (for 2000 ppm MgSO 4). Moreover, the ion selectivity of Na+/Mg2+ and Na+/Ca2+ of the BTC membrane is as high as 126 and 31.5, respectively. These are much higher than those of the related TMC and commercial nanofiltration membranes. Fouling experiments indicate that the flux decline rate (FDR) of the aliphatic polyamide membrane is only 38%, whereas the FDR of the full-aromatic polyamide membrane is 60%. Further investigations confirmed that surface roughness is the main factor affecting the fouling behaviors of polyamide membranes. Our results demonstrate that BTC and HTeC monomers are unique potential materials in the fabrication of nanofiltration membranes used for water treatment such as water softening and ion sieving. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights: • Novel azlactone-functionalized monomer (TMDMA) was designed and synthesized. • The resulting membrane showed decreased surface charge and narrow pore size. • The Ca2+ and Mg2+ rejection rate of the fabricated membrane was increased. • The resulting membrane still maintained higher water flux. • Antifouling property of the fabricated membranes were also enhanced. Abstract Semi-aromatic polyamide membranes have been widely commercialized and used in water treatment processes. Such membranes often have poor Ca2+ and Mg2+ rejection rates due to their intrinsic structural characteristics. Most approaches used to improve rejection are only focused on one kind of repulsion effect: lack of synergism. Thus, the enhancement of rejection is not remarkable. Herein, a novel monomer, trimesoyl-[4,4-dimethyl-5(4H)-azlactone] (TMDMA), was synthesized and used as a secondary reaction molecule in the interfacial reaction for simultaneously improving the steric hindrance and lowering the electrostatic attraction of semi-aromatic polyamide membranes. With the introduction of TMDMA, the mean effective pore size of the polyamide membrane is decreased from 0.23 nm to 0.18 nm. Moreover, the significantly decreased negative surface charge of the fabricated polyamide membrane is observed since the carboxyl from hydrolysis of the azlactone exhibits a higher pKa (acidity coefficient) than that of the benzoic acid. The desalination experiments reveal that the Ca2+ and Mg2+ rejection of the resulting membranes are increased by 26% (from 71.0% to 97%) and 14.0% (from 83% to 97%), respectively, while the water fluxes are maintained at 192 and 167 kg m−2 h−1 MPa−1, demonstrating a satisfactory water softening performance that exceeds commercial nanofiltration membranes. Additionally, the fabricated polyamide membranes can significantly resist the flux decline during fouling experiment that normally results from the deposition of Ca2+−foulant. [ABSTRACT FROM AUTHOR]

Thin-film nanocomposite (TFN) membrane based on polyamide (PA) chemistry was widely applied for water purification and desalination process due to the improved water permeance. It remains a great challenge to significantly enhance rejection because of the non-selective defects caused by the aggregation of nanomaterials in the PA layer. Novel interlayer-based TFN (iTFN) membrane containing nanomaterial interlayer between the porous substrate and PA layer is the promising candidate to improve PA integrity and thus overcome the ubiquitous trade-off between permeability and selectivity. The nanomaterial interlayer not only promotes the subsequent interfacial polymerization (IP) but also provides improved pathways for water transport, which leads to simultaneous improvement in membrane permeability and selectivity. This review systematically categorizes nanomaterial interlayers into three types according to construction methods, namely, direct deposition, in situ growth and functional group-anchored in situ assembly (FAISA). The mechanism of interlayer modulating IP process and PA structure, as well as the effects on water transport, are comprehensively analyzed. Encouraging results reveal that using MOFs interlayer prepared by FAISA is the most promising way to break the trade-off in manufacturing reverse osmosis membranes. Finally, challenges and future efforts are presented for advancing iTFN membranes. [Display omitted] • Recent advances in the porous nanomaterial interlayer enhanced iTFN membranes have been summarized. • Nanomaterial interlayers are categorized into three types according to the construction methods. • The effects of nanomaterial interlayer on interfacial polymerization and separation performance have been explored. • Functional group-anchored in situ assembly MOFs interlayer is a promising candidate to overcome the trade-off between membrane permeability and selectivity. • Challenges and future efforts of promoting nanomaterial interlayer-based iTFN membranes are proposed. [ABSTRACT FROM AUTHOR]

Membrane separation technologies featuring environmentally friendly and highly efficient processes have been widely adopted for sustainable development. Non-linear macromolecules, represented by aromatic poly(amidoamine) dendrimers (ArPD), have good potential for increasing the porosity of the active layer in thin-film composite (TFC) membranes. However, they are often difficult to use as the sole monomer in interfacial polymerization to prepare membranes with high separation accuracy. Herein, the DMF/H 2 O system was determined to resolve the problem of ArPD dissolution, and the behavioral differences of ArPD for different generations in film-forming were then elucidated. For G4 (the fourth generation of ArPD) -TMC (trimesoyl chloride) membranes, the good sieving performance is attributed to the relatively dense polyamide networks from interfacial polymerization, and the continuous pore channels from the tightly packed macromolecules. Therefore, the final polyamide layer shows significant heterogeneity. Moreover, a "patching" strategy was employed to further improve the separation performance. The ArPD-based membranes exhibit about 3 times higher permeance than MPD (m-phenylenediamine)-based membranes under the comparable NaCl rejection. For the repaired membrane, the water permeance reaches 3.2 L m−2 h−1 bar−1 with the NaCl rejection of about 94.9%, which is advantageous compared with reported macromolecule-based membranes. The repaired membrane also shows excellent performance in the removal of small organics in organic solvent system. For example, the methanol permeance achieves 1.5 L m−2 h−1 bar−1 with the rejection to potassium cinnamate (186.25 g mol−1) about 90.3%. This work provides a typical paradigm for the application of macromolecules in the preparation of TFC membranes. [Display omitted] • An aromatic poly(amidoamine) dendrimer (ArPD) served as the sole amine monomer to participate in IP reaction. • The active layer of G4 (the fourth generation of ArPD) -TMC membrane shows significant heterogeneity. • A "patching" strategy was used to further improve the separation performance. • ArPD-based membranes show good performance in desalination and removal of organics. [ABSTRACT FROM AUTHOR]

Conventional thin-film composite (TFC) reverse osmosis (RO) membranes prepared by ultrafast and uncontrolled interfacial polymerization (IP) generally have unsatisfactory permeability and high fouling propensity, which distinctly impedes their development and wide application. Controllable thickness and roughness offer an opportunity to optimize the permeability and fouling resistance of RO membranes. In this work, we propose spin-coating assisted multilayer interfacial polymerization (SMIP) as a promising approach to fabricating high-performance RO membranes using polyethyleneimine (PEI) and 1, 3, 5-benzoyl chloride (TMC). SMIP integrates the high efficiency and uniformity of spin-coating technology, the nano-level and individual properties control of multilayer interfacial polymerization, and the simplicity of the IP process. Combining the strong hydrophilicity with low diffusion efficiency and positive charge of PEI, a thin, intrinsically hydrophilic, smoother and almost electro-neutral polyamide (PA) nanofilm was obtained. The optimal RO membrane with a controlled thickness of the selective layer (≈61 nm) has a water permeance of 3.12 L m−2 h−1 bar−1 and an acceptable NaCl rejection of 97.5%, while the strong hydrophilicity, minimal surface roughness and almost neutral surface charge afford it excellent fouling resistance. SMIP technology not only provides a new approach to preparing highly permeable and low-fouling RO membranes using macromolecular monomers, but also has great application potential in other separation membranes due to its precise control of the selective layer. [Display omitted] • A novel RO membrane was fabricated by spin-coating assisted multilayer interfacial polymerization (SMIP) with PEI and TMC. • The prepared RO membrane featured controllable thickness, minimal surface roughness and electro-neutral surface at pH 6–7. • Molecular simulation results showed that the SMIP increased the cross-linkage of the polyamide layer. • The RO membrane exhibited high permeability and excellent antifouling properties. • SMIP provides an approach for the controllable preparation of high-performance RO membranes. [ABSTRACT FROM AUTHOR]

• The HKUST-1 interlayer improves the hydrophilicity and porosity of the support membrane. • The HKUST-1 interlayer controls the diffusion of piperazine during interfacial polymerization. • TFC membranes with HKUST-1 interlayer significantly increase the penetration flux of organic solvents. Organic solvent nanofiltration (OSN) has a good application prospect in the field of organic solvent separation, but low organic solvent permeance is the main obstacle restricting its application. This work reports a thin film composite (TFC) nanofiltration membrane prepared by interfacial polymerization (IP) on the HKUST-1 MOF interlayer grown in situ on a crosslinked polyimide (PI) substrate. The MOF interlayer improves the hydrophilicity and porosity of the support membrane. In addition, the MOF interlayer controls the diffusion of piperazine (PIP) during the IP process, which induced to form a thin and highly crosslinked polyamide (PA) separation layer. The increased effective membrane area and the reduced thickness of PA separation layer resulted in a methanol permeation flux up to 9.59 L·m−2·h−1·bar−1, while maintaining the rejection of the negatively charged Brilliant Blue G 250 dye (MW = 858.05 g·mol−1) at 98.8%. Furthermore, the stability of the TFC membranes in polar aprotic solvents such as N, N-dimethylformamide highlights their potential for OSN applications in chemical industries. [ABSTRACT FROM AUTHOR]