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• Novel polyarylate NF membranes were prepared with oligomeric phenolic resin monomer. • NF membrane exhibited a high Na 2 SO 4 rejection rate and excellent chlorine-resistance. • The influence of preparation parameters on the NF membrane performance was investigated. Conventional water treatment polyamide nanofiltration (NF) membranes often suffer from the degradation of sodium hypochlorite (NaOCl) in sewage or during the process of membrane cleaning and deteriorate the separation performance, which significantly increases the treatment cost. Herein, a novel polyacrylate composite NF membranes were prepared by interfacial polymerization using oligomeric phenolic resin (OPR) and trimesoyl chloride (TMC) as aqueous and organic phase monomer respectively on the polyethersulfone (PES) ultrafiltration supporting membranes. The fabrication parameters, including the pH of the aqueous solution, reaction time and the concentration of the monomer, on the performance of the composite NF membranes were optimized. A series of characterization indicated that the surface of the NF membranes was negatively charged, the molecular weight cut-off (MWCO) and the pore diameter of the polyacrylate membrane were 400 Da and 0.47 nm, respectively. At the optimized preparation conditions, the NF membrane exhibited high Na 2 SO 4 rejection of 98.2% and water flux of 2.42L·m−2·h−1·bar−1, which was superior to most of the polyacrylate NF membranes reported in recent years. Compared with the polyamide membrane, the prepared polyacrylate membrane demonstrated better chlorine-resistant property and still maintained 92.0% Na 2 SO 4 rejection after being treated with NaOCl solution. Moreover, the NF membrane preserved excellent long-term operation stability. The chlorine-resistant NF membrane constructed from OPR monomer has a broad application prospect in the field of high chlorine wastewater treatment. [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 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]

Abstract Polyamide membranes based on trimesoyl chloride (TMC) have captured the majority of the market share for desalination in water treatment. The TMC based membrane is prone to form calcium bridges with the organic foulants due to the relatively strong deprotonation ability of the benzoic acid generated from the incomplete reaction of the acyl chloride monomers. The foulants are thus rapidly deposited on the surface of the TMC based membrane, which results in the deterioration of water production and decrease of membrane lifespan. Herein, we have fabricated a polyamide membrane based on novel trimesoyl-[4,4-dimethyl-5(4H)-azlactone] (TMDMA) monomer instead of TMC monomer. Since the carboxylic groups of the prepared TMDMA polyamide nanofilm are not directly connected to the phenyl ring, the acidity coefficient (p K a ) value is higher and, consequently, deprotonation ability is expected to be weaker. To confirm this theory, we have conducted the fouling experiment on TMDMA based membrane using alginate as a model foulant and compared that with TMC based polyamide membranes. A lower flux decline (33%) and higher cleaning efficiency (90.72%) are observed for the TMDMA polyamide membrane, while the flux decline and cleaning efficiency for the TMC based polyamide membrane are 52% and 49.52% respectively. Furthermore, the average Ca2+ density of the TMDMA polyamide membrane surface before and after cleaning are 81.52 mg m−2 and 21.61 mg m−2 respectively, which are lower than that of the TMC based polyamide membrane surface. Thus, it is clearly showing that the surface of the TMDMA polyamide membrane is not prone to form calcium bridges with foulants due to the weaker complexation between Ca2+ and the carboxylic acid groups. Graphical abstract Image 1 Highlights • Novel non-trimesoyl chloride based polyamide were fabricated by interfacial polymerization. • The novel membrane showed lower flux decline and higher cleaning efficiency than that of TMC based polyamide membranes. • Significantly reduced Ca2+ deposition density was observed on the surface of the novel membrane. [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]