Zwitterionic functionalized layered double hydroxides nanosheets for a novel charged mosaic membrane with high salt permeability

An eco-friendly hydroentangled cotton non-woven membrane with alginate hydrogel for water filtration

Alginate hydrogel is highly efficient for water filtration due to its anti-fouling nature and formation of strong hydration membranes. However, poor mechanical properties of alginate hydrogel membrane limit its installation in water treatment. There is a need to enhance mechanical properties of alginate hydrogel membranes using eco-friendly, cost-effective materials and technologies. In this work, hydroentangled non-woven from cotton waste (comber noil) fibers was prepared. This non-woven was immersed in solution of sodium alginate (0.5 %, 1 %, 1.5 %) followed by dipping in calcium chloride solution which resulted in gel formation on and into cotton fibers. The successful formation of gel on non-woven fabric was confirmed through FTIR (Fourier transform infrared spectroscopy) and properties of this composite membrane were analyzed by SEM (Scanning electron microscopy), XRD (X-ray diffraction), DSC (Differential scanning calorimeter), water contact, water flux, oil-water filtration, air permeability, tensile strength, and porosity tests. The results showed that porosity of prepared hydrogel membranes decreased with increasing alginate concentration from 0.5 % to 1.5 % which resulted in decreased water permeation flux from 2655 h-1/m2 to 475 h-1/m2. The prepared membrane has separation efficiencies for the oil-water mixture in the range of 97.5 % to 99.5 %. Moreover, the developed samples also showed significant antibacterial activity as well as improved mechanical properties. The strength of the prepared membrane is in the range of 40 N to 80 N. The developed sodium alginate hydrogel-based non-woven membrane could have potential applications for commercial water filtration systems.

Polyvinyl alcohol and sodium alginate hydrogel coating with different crosslinking procedures on a PSf support for fabricating high-flux NF membranes

Polyvinyl alcohol (PVA) and sodium alginate (SA) hydrogel-coated nanofiltration (NF) membranes with high-flux and permselectivity were prepared. The coating of PVA and SA hydrogel selective layer on a porous polysulfone (PSf)/non-woven fabric ultrafiltration substrate membrane was conducted through different three procedures including pre-crosslinking, in-situ crosslinking, and immersing crosslinking and the use of glutaraldehyde as a crosslinking agent. The properties and performances of all types of the prepared membranes were evaluated through ATR-FTIR spectroscopy, AFM, SEM, zeta potential, contact angle, and cross-flow permeation tests. The immersing technique resulted in the formation of TFC membranes with higher hydrophilicity, smoother surface layer, higher negative charge, higher permeation flux, higher salt rejection and better anti-fouling performance. Also, the higher negative surface charge of the immersing coated TFC membranes due to dissociation of hydrophilic functional groups of the PVA and SA hydrogel selective layer resulted in higher As(III) rejection. SA coated NF membrane through immersing method exhibited a higher pure water permeability of 11.2 L m^-2 h^-1 bar^-1, NaCl, MgSO₄, and Na₂SO₄ rejection of 38.2%, 55.1%, and 70.4%, respectively with As(III) rejection of 60.6%. All types of the PVA and SA hydrogel-coated PSf membranes possessed improved fouling resistance to BSA aqueous solution, superior anti-fouling performance was obtained with SA hydrogel coating through immersing method. Such optimum membranes indicated high stability in the long-term experiments. This study showed that the coating of the SA hydrogel layer on a PSf support through immersing method could be a promising candidate for fabricating high-flux NF membranes.

Effect of different factors on treatment of oily wastewater by TiO2/Al2O3-PVDF ultrafiltration membrane

An ultrafiltration membrane developed by our research group was applied to treat simulated emulsified oil wastewater. ATR-FTIR, SEM, TEM, and Zeta potential analyzes demonstrated that the modified ultrafiltration membrane (MM) has excellent stability and anti-fouling capacity than origin membrane (OM), which possesses a pure water flux of 260 L·m^-2·h^-1 and oil/water (o/w) rejection of 98.5 ± 0.33%. Inorganic salt CaCl₂ has more considerable influence than MgSO₄ and NaCl under the same mass concentration in the two membranes UF process. Along with concentration increasing, flux sharply reduces; meanwhile, the rejection has an opposite trend. Moreover, permeation flux has a maximum value, and the rejection also gets its optimal state under neutral conditions during the pH value of 2-12. The membrane also exhibits excellent anti-fouling performance and anti- o/w adsorption properties with an adsorption rate below 0.8% compared with OM, which has an adsorption rate of nearly 2.1%, respectively. A kind of new UF membrane developed by our research group was applied to treat simulated o/w. ATR-FTIR, SEM, TEM, and Zeta potential analyzes demonstrated that PVDF-Al₂O₃/TiO₂ material has excellent stability and anti-fouling capacity. CaCl₂ has the greatest influence than MgSO₄ and NaCl under the same mass concentration. Moreover, permeation flux has maximum value and the rejection also gets its optimal state under neutral conditions during pH 2-12. The membrane also exhibits excellent anti-fouling performance and anti-O/W adsorption properties with adsorption rate below 0.8% compared with OM which has an adsorption rate nearly 2.1%, respectively.

Principles of reverse electrodialysis and development of integrated-based system for power generation and water treatment: a review

Reverse electrodialysis (RED) is among the evolving membrane-based processes available for energy harvesting by mixing water with different salinities. The chemical potential difference causes the movement of cations and anions in opposite directions that can then be transformed into the electrical current at the electrodes by redox reactions. Although several works have shown the possibilities of achieving high power densities through the RED system, the transformation to the industrial-scale stacks remains a challenge particularly in understanding the correlation between ion-exchange membranes (IEMs) and the operating conditions. This work provides an overview of the RED system including its development and modifications of IEM utilized in the RED system. The effects of modified membranes particularly on the psychochemical properties of the membranes and the effects of numerous operating variables are discussed. The prospects of combining the RED system with other technologies such as reverse osmosis, electrodialysis, membrane distillation, heat engine, microbial fuel cell), and flow battery have been summarized based on open-loop and closed-loop configurations. This review attempts to explain the development and prospect of RED technology for salinity gradient power production and further elucidate the integrated RED system as a promising way to harvest energy while reducing the impact of liquid waste disposal on the environment.

Layered double hydroxides and related hybrid materials for removal of pharmaceutical pollutants from water

Pharmaceuticals and their by-products are recalcitrant contaminants in water. Moreover, the high consumption of these drugs has many detrimental effects on body waters and ecosystems. In this timely review, the advances in molecular engineering of layered double hydroxides (LDH) that have been used for the removal of pharmaceutical pollutants are discussed. The approach starts from the strategies to obtain homogeneous synthesis of LDH that allow the doping and/or surface functionalization of different metals and oxides, producing heterojunction systems as well as composites with carbon and silica-based materials with high surface area. Adsorption is considered as a traditional removal of pharmaceutical pollutants, so the kinetic and mechanism of this phenomenon are analyzed based on pH, temperature, ionic strength, in order to obtain new insights for the formation of multifunctional LDH. Advanced oxidation methodologies, mainly heterogeneous photocatalysis and Fenton-like processes, stand out as the more efficient even to obtain the mineralization of the drugs. The LDH have the advantage of structural memory that favors regeneration processes. The reconstruction of calcined LDH can be used to improve drug removal, through a combination of adsorption capacity/catalytic activity. A meticulous analysis of the persistence, toxicity and bioaccumulation of the most common pharmaceuticals has allowed us to highlight the ability of the LDH to remove recalcitrant drugs at relatively low concentrations (ppm, ppb), in contrast to other mixed oxide nanostructures and homogeneous oxidation processes. In this sense, the mechanism of drug removal by LDH is discussed based on the importance of the use of composites, scavenger agents, Fenton and electro-Fenton processes, membranes, thin films and coatings, among others. In addition, the ecotoxicity of LDH is also reviewed to indicate that these layered structures can exhibit biocompatibility or high toxicity depending on the adsorbed drug and ions/metals that compose them. Undoubtedly, the LDH have a unique flexible structure with adsorption capacity and catalytic activity, facts that explain the important reasons for their extensive use in the environmental remediation of pharmaceutical pollutants from water.

Silica Containing Composite Anion Exchange Membranes by Sol-Gel Synthesis: A Short Review

This short review summarizes the literature on composite anion exchange membranes (AEM) containing an organo-silica network formed by sol–gel chemistry. The article covers AEM for diffusion dialysis (DD), for electrochemical energy technologies including fuel cells and redox flow batteries, and for electrodialysis. By applying a vast variety of organically modified silica compounds (ORMOSIL), many composite AEM reported in the last 15 years are based on poly (vinylalcohol) (PVA) or poly (2,6-dimethyl-1,4-phenylene oxide) (PPO) used as polymer matrix. The most stringent requirements are high permselectivity and water flux for DD membranes, while high ionic conductivity is essential for electrochemical applications. Furthermore, the alkaline stability of AEM for fuel cell applications remains a challenging problem that is not yet solved. Possible future topics of investigation on composite AEM containing an organo-silica network are also discussed.

High-efficiency CO2 separation using hybrid LDH-polymer membranes

Membrane-based gas separation exhibits many advantages over other conventional techniques; however, the construction of membranes with simultaneous high selectivity and permeability remains a major challenge. Herein, (LDH/FAS)_n-PDMS hybrid membranes, containing two-dimensional sub-nanometre channels were fabricated via self-assembly of unilamellar layered double hydroxide (LDH) nanosheets and formamidine sulfinic acid (FAS), followed by spray-coating with a poly(dimethylsiloxane) (PDMS) layer. A CO₂ transmission rate for (LDH/FAS)₂₅-PDMS of 7748 GPU together with CO₂ selectivity factors (SF) for SF(CO₂/H₂), SF(CO₂/N₂) and SF(CO₂/CH₄) mixtures as high as 43, 86 and 62 respectively are observed. The CO₂ permselectivity outperforms most reported systems and is higher than the Robeson or Freeman upper bound limits. These (LDH/FAS)_n-PDMS membranes are both thermally and mechanically robust maintaining their highly selective CO₂ separation performance during long-term operational testing. We believe this highly-efficient CO₂ separation performance is based on the synergy of enhanced solubility, diffusivity and chemical affinity for CO₂ in the sub-nanometre channels.

High efficient dye removal with hydrolyzed ethanolamine-Polyacrylonitrile UF membrane: Rejection of anionic dye and selective adsorption of cationic dye

The dye-water treatment using UF membrane is still a challenge. In the present study, the optimized PAN-ETA ultrafiltration membrane was hydrolyzed and subsequently characterized by SEM, IR, CA, XPS, NMR, mechanic measurement, etc. The obtained membrane (H-PAN-ETA) was used for dye removal and it showed both an excellent anti-dye fouling and a good rejection property for anionic dyes. I.e. 96% rejection for methyl blue (MB), 99% for congo red (CR), 94% for acid fuchsin (AF) with no sign of contamination by dye. The flux of H-PAN-ETA membrane maintained at 50-53 L m^-2⋅ h^-1 during a 10-h filtration, which is higher than that of tight UF membranes reported. Meanwhile, H-PAN-ETA membrane was able to selectively remove cationic dyes, such as methylene blue (MEB), rhodamine B (RB) and, crystal violet (CV), or the mixture of anionic dye/cationic dye by adsorption process. Its adsorption capacity remained unchanged after 20 cycles. Finally, the immobile electrical double layer (EDL) theory combined with electrostatic force was introduced to explain the separation mechanism of charged UF membrane, which is helpful to instruct the preparation of UF membrane for dye removal.

Carbodiimide-assisted zwitterionic modification of poly(piperazine amide) thin-film composite membrane for enhanced separation and anti-depositing performances to cationic/anionic dye aqueous solutions

In this work, a novel method of carbodiimide-assisted zwitterionic modification was proposed and implemented to incorporate zwitterionic moieties onto poly(piperazine amide) membrane for improved water permeability and anti-depositing property, which are crucial for highly efficient nanofiltration of dye-contained effluents. Carboxyl groups of polyamide layer were firstly transferred into N-acylurea using excess l-ethyl-3-(3-(dimethylamino)propyl)-carbodiimide. Zwitterions were then incorporated through ring-opening reaction between tertiary amine groups of N-acylurea and 1, 4-butanesultone. Carbodiimide-assisted zwitterionic modification was verified by ATR-IR and XPS analyses and was found to not affect membrane pore size but significantly enhance membrane's permeation and anti-dye-deposition performances. Compared with those of virgin membrane, water permeabilities of the desired zwitterionic membrane to pure water, Congo red aqueous solution and Victoria blue B aqueous solution were higher by 42.9, 62.3 and 95.2 %, respectively, hydraulic resistances from irreversible deposition of Congo red and Victoria blue B molecules were dramatically lowered by 68.4 and 91.8 %, respectively. Furthermore, the perm-selectivity performance of the desired zwitterionic membrane in terms of molecular weight cut-off and pure water permeability was better than most of the reported zwitterionic membranes, and the separation and anti-depositing performances to both anionic and cationic dye aqueous solutions were better than commercial membrane NF270.

PIP/TMC Interfacial Polymerization with Electrospray: Novel Loose Nanofiltration Membrane for Dye Wastewater Treatment

A loose nanofiltration (NF) membrane with excellent dye rejection and high permeation of inorganic salt is required to fractionate dye/salt mixture in dye wastewater treatment. In this study, we fabricated the loose NF membrane by using the electrospray interfacial polymerization (EIP) method. It is a novel and facile interfacial polymerization method, which controls the thickness of the poly(piperazine-amide) (PPA) layer in nanometers (1 nm/min) and changes cross-linking degree of PPA layer and pore size by varying the electrospray time; consequently, water permeance and dye/salt rejection ratio can be handled. The fabricated EIP membrane with an optimized fabrication condition (M30, electrospray time was 30 min) possessed excellent pure water permeance (20.2 LMH/bar), high dye rejection (e.g., 99.6% for congo red (CR)), and low salt rejection (e.g., 6.3% for NaCl). Moreover, the EIP membrane exhibited enhanced antifouling property than commercial NF membrane (NF90) with a high flux recovery rate (FRR) of 87.1% and low irreversible fouling (R_ir) of 12.9% after fouled by bovine serum albumin (BSA) due to its great smooth surface (average roughness (R_a) is 12.2 nm), hydrophilicity property, enhanced zeta potential, and low protein adsorption. The results indicate that the EIP loose NF membrane had a high potential for dye wastewater treatment.

One-step synthesis of zwitterionic graphene oxide nanohybrid: Application to polysulfone tight ultrafiltration hollow fiber membrane

In this paper, novel zwitterionic graphene oxide (GO) nanohybrid was synthesized using monomers [2-(Methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide (SBMA) and N,N′-methylenebis(acrylamide) (MBAAm) (GO@poly(SBMA-co-MBAAm), and incorporated into polysulfone (PSF) hollow fiber membrane for the effectual rejection of dye from the wastewater. The synthesized nanohybrid was characterized using FT-IR, PXRD, TGA, EDX, TEM and zeta potential analysis. The occurrence of nanohybrid on the membrane matrix and the elemental composition were analyzed by XPS. The as-prepared tight ultrafiltration hollow fiber membrane exhibited high rejection of reactive black 5 (RB-5, 99%) and reactive orange 16 (RO-16, 74%) at a dye concentration of 10 ppm and pure water flux (PWF) of 49.6 L/m²h. Fabricated nanocomposite membranes were also studied for their efficacy in the removal of both monovalent (NaCl) and divalent salts (Na₂SO₄). The results revealed that the membrane possesses complete permeation to NaCl with less rejection of Na₂SO₄ (<5%). In addition, the nanocomposite membrane revealed outstanding antifouling performance with the flux recovery ratio (FRR) of 73% towards bovine serum albumin (BSA). Therefore, the in-house prepared novel nanocomposite membrane is a good candidate for the effective decolorization of wastewater containing dye.

Custom-Tailoring Loose Nanofiltration Membrane for Precise Biomolecule Fractionation: New Insight into Post-Treatment Mechanisms

Loose nanofiltration (NF) membranes with diverse selectivity can meet the great demands in various bioseparation applications. Thus, a facile strategy to tune the properties such as pore size, surface charge, and hydrophilicity of the NF membrane is required to produce tailor-made loose NF membranes without changing the existing production line. Herein, we systematically investigated the post-treatment of the nascent poly(piperazine amide) NF membranes using different reagents (organic acids, weak bases, organic solvents and ionic liquid (IL)). Various characterizations revealed that the skin/separation layer became looser and permeance was promoted with the decrease of salt rejection in varying degrees. It was found that the O/N ratio did not rigorously represent the cross-linking degree of the skin layer, because besides the hydrolysis of the residual acyl chloride impeding the amido bond formation, the breaking of existing amido bonds and the grafting of free trimesoyl chloride molecules on the nascent membranes could also increase the O/N ratio during post-treatments. Then three mechanisms including hydrolysis, swelling rearrangement and capping reaction effects were proposed to better understand the membrane properties variations. All these effects resulted in larger pore size of the NF membrane, and the hydrolysis/capping effect might increase negative charge and hydrophilicity on the membrane, while the swelling rearrangement could produce less defective skin structure. These three effects might be involved together during a single treatment. Finally, the NF membrane post-treated by N-hexane could efficiently separate antibiotics and NaCl with the highest permeate flux, whereas the one post-treated by ionic liquid outperformed others for the decoloration of cane molasses (much more efficient than NF270, DL, and NTR7450 membranes). The long-term operating stability of the post-treated membranes selected was also confirmed by a continuous crossflow filtration for 15 h with regular alkaline cleaning.

Interfacial Junctions Control Electrolyte Transport through Charge-Patterned Membranes

Distinct transport mechanisms emerge when nanostructured substrates are patterned with multiple chemistries. For example, charge-patterned mosaic membranes possess surfaces functionalized with discrete domains of both positive and negative charge. These oppositely charged domains provide pathways for both the cation and anion from a dissolved salt to permeate through the membrane without violating the macroscopic constraint of electroneutrality. Here, by systematically varying the geometry and size of the charge pattern, we elucidate the molecular interactions that promote the transport of salts under the action of pressure-driven flow. For patterns that consist of equivalent areal coverages of positively charged and negatively charged domains, the effects of the geometric parameters were encapsulated in a single variable, the interfacial packing density, that quantified the fraction of the membrane surface covered by junctions between oppositely charged domains. Experimentally, the transport of symmetric electrolytes (i.e., KCl and MgSO₄) increased with the value of the interfacial packing density, while the interfacial packing density did not significantly affect the transport of asymmetric electrolytes (i.e., K₂SO₄ and MgCl₂). Simulations of the electrical potential near the membrane surface demonstrate that for symmetric electrolytes the structural charge heterogeneity reduces the barrier to ion partitioning, thereby promoting salt transport through the membranes. For asymmetric electrolytes, the charge heterogeneity skews the local availability of ions from the stoichiometric ratio of the salt, thus hindering salt transport. These findings demonstrate the promise of accessing transport mechanisms, which could find utility in a diverse range of chemical separations and sensing applications, through chemical patterning of membranes.

MgAl-Layered-Double-Hydroxide/Sepiolite Composite Membrane for High-Performance Water Treatment Based on Layer-by-Layer Hierarchical Architectures

One of the major challenges in the removal of organic pollutants is to design a material with high efficiency and high flux that can remove both cationic and anionic dyes, oil-in-water (O/W) emulsion and heavy metal ions. Herein, we constructed novel chemically stabilized MgAl-layered-double-hydroxide/sepiolite (MgAl-LDH/Sep) composite membranes via 3D hierarchical architecture construction methods. These membranes were analyzed by scanning electron microscopy (SEM), atomic force microscopy (AFM) and X-ray diffraction (XRD), etc. Benefiting from the presence of hydrophilic functional groups on the surface of the film, the membranes show an enhanced water flux (~1200 L·m⁻² h⁻¹), while keeping a high dyes rejection (above 99.8% for anionic and cationic dyes). Moreover, the CA membrane coupled with MgAl-LDH/Sep exhibits a multifunctional characteristic for the efficient removal of mesitylene (99.2%), petroleum ether (99.03%), decane (99.07%), kerosene (99.4%) and heavy metal ion in water due to the layer-by-layer sieving. This hierarchical architecture is proved to have excellent environmental and chemical stability. Therefore, the membrane has potential in the treatment of sewage wastewater.

Functionalized Graphene Oxide Modified Polyethersulfone Membranes for Low-Pressure Anionic Dye/Salt Fractionation

In this study, polyelectrolyte assembled functionalized graphene oxide (PE-GO) membranes were fabricated through a one-step charge facilitated deposition method for high performance dye/salt separation. According to the intercalation of polydopamine (PDA) and (ionic liquid) IL functional moieties into the GO membranes, the pore size of the resulted PE-pGO and PE-iGO membrane increased from 2.69 nm to 4.13 nm and 6.54 nm, respectively. Correspondingly, a pure water flux of 13.8 ± 2.2, 36.7 ± 3.4, and 52.1 ± 6.7 L m⁻¹ h⁻¹ bar⁻¹ was achieved for PE-GO, PE-pGO and PE-iGO membrane, respectively. PE-iGO membrane with the largest pore size could be operated with significant water permeability (28.3 to 38.3 L m⁻¹ h⁻¹ bar⁻¹) at a low operating pressure range of 0.5–2 bar (dye concentration = 100 ppm, salt concentration = 5 g/L). More importantly, functionalities introduced to the GO nanosheets are found to impact the dye adsorption to the membrane surface. The IL intercalation promotes the elution of dye molecules from the IL moieties at elevated pH, therefore enhancing the efficiency of alkaline washing of the membrane. By contrast, the intercalation of PDA weakens such efficiency due to its strong adhesion force to the dye molecules even at the alkaline condition.

Establishment of transport channels with carriers for water in reverse osmosis membrane by incorporating hydrotalcite into the polyamide layer

Hydrotalcite incorporated in polyamide layer of RO membrane facilitates the transport of water.

Influence of l-lysine on the permeation and antifouling performance of polyamide thin film composite reverse osmosis membranes

Polyamide thin film composite (TFC) reverse osmosis (RO) membranes were prepared in this study. l-Lysine is used as a type of aqueous additive during interfacial polymerization. As a result, the pure water flux (PWF) of the resulting membranes increased by around 18% and their salt rejection improved from 98.17% to 98.40% at an optimum l-lysine dosage of 0.1 wt%. Additionally, the anti-fouling properties of the resulting membranes were enhanced. The chemical structure of the membranes was investigated using attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS). The morphologies of the top surface and cross-section of the membranes were revealed by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and atomic force microscopy (AFM). Furthermore, contact angle (CA) and zeta potential measurements were carried out to determine the surface properties of the membranes. The results showed that the TFC RO membrane became thinner, smoother, smaller in surface area, more hydrophilic and more negatively charged after the introduction of l-lysine. Accordingly, the reason for the enhancement in the PWF and anti-fouling properties of the TFC RO membranes with the introduction of l-lysine was analyzed. The thinner selective layer (increase in concentration gradient across the membrane) with carboxyl groups (hydrogen bond interactions) and loose structure (greater free volume and sub-nanometer pores) resulted in low hydraulic resistance to the permeability of the polyamide selective layer, which led to the enhancement in PWF. Also, the smoother and more hydrophilic top surface and the increase in negative charges in the selective layer contribute to the improvement in anti-fouling property.

Polyamide thin film composite (TFC) reverse osmosis (RO) membranes were prepared in this study.

Recent Advances in the Fabrication of Membranes Containing "Ion Pairs" for Nanofiltration Processes

In the face of serious environmental pollution and water scarcity problems, the membrane separation technique, especially high efficiency, low energy consumption, and environmental friendly nanofiltration, has been quickly developed. Separation membranes with high permeability, good selectivity, and strong antifouling properties are critical for water treatment and green chemical processing. In recent years, researchers have paid more and more attention to the development of high performance nanofiltration membranes containing “ion pairs”. In this review, the effects of “ion pairs” characteristics, such as the super-hydrophilicity, controllable charge character, and antifouling property, on nanofiltration performances are discussed. A systematic survey was carried out on the various approaches and multiple regulation factors in the fabrication of polyelectrolyte complex membranes, zwitterionic membranes, and charged mosaic membranes, respectively. The mass transport behavior and antifouling mechanism of the membranes with “ion pairs” are also discussed. Finally, we present a brief perspective on the future development of advanced nanofiltration membranes with “ion pairs”.

Novel, one-step synthesis of zwitterionic polymer nanoparticles via distillation-precipitation polymerization and its application for dye removal membrane

In this work, poly(MBAAm-co-SBMA) zwitterionic polymer nanoparticles were synthesized in one-step via distillation-precipitation polymerization (DPP) and were characterized. [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide (SBMA) as monomer and N, N′-methylene bis(acrylamide) (MBAAm) as cross-linker are used for the synthesis of nanoparticles. As  far as our knowledge, this is the first such report on the synthesis of poly(MBAAm-co-SBMA) nanoparticles via DPP. The newly synthesized nanoparticles were further employed for the surface modification of polysulfone (PSF) hollow fiber membranes for dye removal. The modified hollow fiber membrane exhibited the improved permeability (56 L/ m² h bar) and dye removal (>98% of Reactive Black 5 and >80.7% of Reactive orange 16) with the high permeation of salts. Therefore, the as-prepared membrane can have potential application in textile and industrial wastewater treatment.

Development of Hybrid Ultrafiltration Membranes with Improved Water Separation Properties Using Modified Superhydrophilic Metal-Organic Framework Nanoparticles

Metal-organic frameworks (MOFs) are being intensively explored as filler materials for polymeric membranes primarily due to their high polymer affinity, large pore volumes, and alterable pore functionalities, but the development of MOF-based ultrafiltration (UF) membranes for water treatment lags behind. Herein, poly(sulfobetaine methacrylate) (PSBMA)-functionalized MOF UiO-66-PSBMA was developed, and incorporated into polysulfone (PSf) casting solution to fabricate novel hybrid UF membranes via phase-inversion method. The resultant UiO-66-PSBMA/PSf membrane exhibited significantly improved water flux (up to 602 L m^-2 h^-1), which was 2.5 times that of the pristine PSf membrane (240 L m^-2 h^-1) and 2 times that of UiO-66-NH₂/PSf membrane (294 L m^-2 h^-1), whereas the rejection of UiO-66-PSBMA/PSf membrane was still maintained at a high level. Moreover, UiO-66-PSBMA/PSf membrane exhibited improved antifouling performance. The improvement of membrane performances could be attributed to the well-tailored properties of UiO-66-PSBMA. On one hand, the excellent dispersion and compatibility of UiO-66-PSBMA ensured the formation of a uniform structure with few defects. On the other hand, the superhydrophilicity of UiO-66-PSBMA could accelerate the exchange rate between solvent and nonsolvent, resulting in a more hydrophilic surface and a more porous structure. Besides, UiO-66-PSBMA nanoparticles in the thin layer provided additional flow paths for water permeation through their hydrophilic porous structure as well as the tiny interspace between PSf matrix. This study indicates the great application potential of UiO-66-PSBMA in fabricating hybrid UF membranes and provides a useful guideline to integrate other modified hydrophilic MOFs to design UF membranes for water treatment.

Nanoscale tailor-made membranes for precise and rapid molecular sieve separation

The precise and rapid separation of different molecules from aqueous, organic solutions and gas mixtures is critical to many technologies in the context of resource-saving and sustainable development. The strength of membrane-based technologies is well recognized and they are extensively applied as cost-effective, highly efficient separation techniques. Currently, empirical-based approaches, lacking an accurate nanoscale control, are used to prepare the most advanced membranes. In contrast, nanoscale control renders the membrane molecular specificity (sub-2 nm) necessary for efficient and rapid molecular separation. Therefore, as a growing trend in membrane technology, the field of nanoscale tailor-made membranes is highlighted in this review. An in-depth analysis of the latest advances in tailor-made membranes for precise and rapid molecule sieving is given, along with an outlook to future perspectives of such membranes. Special attention is paid to the established processing strategies, as well as the application of molecular dynamics (MD) simulation in nanoporous membrane design. This review will provide useful guidelines for future research in the development of nanoscale tailor-made membranes with a precise and rapid molecular sieve separation property.

Surface-Initiated Controlled Radical Polymerization: State-of-the-Art, Opportunities, and Challenges in Surface and Interface Engineering with Polymer Brushes

The generation of polymer brushes by surface-initiated controlled radical polymerization (SI-CRP) techniques has become a powerful approach to tailor the chemical and physical properties of interfaces and has given rise to great advances in surface and interface engineering. Polymer brushes are defined as thin polymer films in which the individual polymer chains are tethered by one chain end to a solid interface. Significant advances have been made over the past years in the field of polymer brushes. This includes novel developments in SI-CRP, as well as the emergence of novel applications such as catalysis, electronics, nanomaterial synthesis and biosensing. Additionally, polymer brushes prepared via SI-CRP have been utilized to modify the surface of novel substrates such as natural fibers, polymer nanofibers, mesoporous materials, graphene, viruses and protein nanoparticles. The last years have also seen exciting advances in the chemical and physical characterization of polymer brushes, as well as an ever increasing set of computational and simulation tools that allow understanding and predictions of these surface-grafted polymer architectures. The aim of this contribution is to provide a comprehensive review that critically assesses recent advances in the field and highlights the opportunities and challenges for future work.

Zeolitic Imidazolate Framework/Graphene Oxide Hybrid Nanosheets Functionalized Thin Film Nanocomposite Membrane for Enhanced Antimicrobial Performance

Inspired by the rational design concept, a novel antimicrobial agent zeolitic imidazolate framework-8 (ZIF-8)/graphene oxide (GO) was synthesized and utilized as a novel and efficient bactericidal agent to fabricate antimicrobial thin film nanocomposite (TFN) membranes via interfacial polymerization. The resultant hybrid nanosheets not only integrates the merits of both ZIF-8 and GO but also yields a uniform dispersion of ZIF-8 onto GO nanosheets simultaneously, thus effectively eliminating the agglomeration of ZIF-8 in the active layer of membranes. A ZIF-8/GO thin film nanocomposite (TFN-ZG) membrane with typical water permeability (40.63 L m(-2) h(-1) MPa(-1)) allows for efficient bivalent salt removal (rejections of Na2SO4 and MgSO4 were 100% and 77%, respectively). Furthermore, the synthesized ZIF-8/GO nanocomposites were verified to have an optimal antimicrobial activity (MIC,128 μg/mL) in comparison with ZIF-8 and GO separately, which sufficiently endowed the TFN-ZG membrane with excellent antimicrobial activity (84.3% for TFN-ZG3). Besides, the antimicrobial mechanisms of ZIF-8/GO hybrid nanosheets and TFN-ZG membranes were proposed. ZIF-8/GO functionalized membrane with high antimicrobial activity and salt retention denoted its great potential in water desalination, and we suggest that ZIF-8 based crystal may offer a new pathway for the synthesis of a multifunctional bactericide.