Nanofiltration membranes via co-deposition of polydopamine/polyethylenimine followed by cross-linking

Novel nitrogen-rich hydrogel adsorbent for selective extraction of rare earth elements from wastewater

Efficient recovery of rare earth elements (REEs) from wastewater is crucial for advancing resource utilization and environmental protection. Herein, a novel nitrogen-rich hydrogel adsorbent (PEI-ALG@KLN) was synthesized by modifying coated kaolinite-alginate composite hydrogels with polyethylenimine through polyelectrolyte interactions and Schiff's base reaction. Various characterizations revealed that the high selective adsorption capacity of Ho (155 mg/g) and Nd (125 mg/g) on PEI-ALG@KLN is due to a combination of REEs (Lewis acids) via coordination interactions with nitrogen-containing functional groups (Lewis bases) and electrostatic interactions; its adsorption capacity remains more than 85 % after five adsorption-desorption cycles. In waste NdFeB magnet hydrometallurgical wastewater, the recovery rate of PEI-ALG@KLN for Nd and Dy can reach more than 93 %, whereas that of Fe is only 5.04 %. Machine learning prediction was used to evaluate adsorbent properties via different predictive models, with the random forest (RF) model showing superior predictive accuracy. The order of significance for adsorption capacity was pH > time > initial concentration > electronegativity > ion radius, as indicated by the RF model feature importance analysis and SHapley Additive exPlanations values. These results confirm that PEI-ALG@KLN has considerable potential in the selective extraction of REEs from wastewater.

Preparation of a CPVC composite loose nanofiltration membrane based on plant polyphenols for effective dye wastewater treatment

The textile industry's high-salinity wastewater presents a significant difficulty for fractioning salts and dyes. To fractionate the dyes and salts, a high-performance CPVC composite loose nanofiltration membrane (LNM) was fabricated by interfacial polymerization. The organic phase was obtained by crosslinking polyethylenimine (PEI) with tannic acid (TA) and gallic acid (GA) using TMC. The resultant composite LNM performance was enhanced by adjusting the coating parameters, which included TA and GA concentrations as well as coating time. The study examined the effects of the total content of TA/PEI and GA/PEI concentrations on the chemical structure, surface roughness, and microstructure of the selective layer of LNM using SEM, AFM, FTIR, and water contact angle measurements. It also investigated the filtration performance of the membrane's selective layer, including pure water flux, PEG800 rejection rate, and membrane fouling analysis. However, the resultant membrane treated simulated reactive black 5 (RB5) dye wastewater. When the total content of TA/PEI is 4 kg L-1, the permeability of pure water flux is high at 7.5 L per m2 per h per bar when the total content of GA/PEI is 14 kg L-1 and the pure water flux is high at 8.8 L per m2 per h per bar. The overall PEG800 rejection rates were 97-98.98%. The optimal TA : PEI ratios reached a good pure water permeability up to 6.4 L per (m2 per h per bar) with a high rejection rate of 99.69% for a ratio 1/3 to dye, and GA : PEI ratios reached a good water permeability at 5.5 and 6.5 L per (m2 per h per bar) with rejection rates of 99.21% and 98.88% for ratio 1/3 and 3.5/10.5 for simulated RB5 dye, and the NaCl retention rate gradually decreased from 4% to 3%. The resultant LNM demonstrated promising applications in dye and salt fractionation.

Tailoring the performance of composite PEI nanofiltration membranes via incorporating activated cyclodextrins

Cyclodextrins (CDs) with unique cavity structures have been used as materials for nanofiltration membrane fabrications. In the present work, the activated CD (O-CD), oxidated by NaIO4, and polyethyleneimine (PEI) were co-deposited on a hydrolyzed polyacrylonitrile support, post-treated by glycerol protection and heating treatment, to prepare nanofiltration membranes with low molecular weight cut-off (MWCO). As the cavities in CD present and the aldehyde groups introduced after oxidation, the O-CDs were expected to crosslink the PEI layer and provide extra permeating channels. The filtration experiments showed that the incorporation of O-CDs improved the permeances of the O-CD-PEI/HPAN nanofiltration membranes. The performance can be tailored by the control of the loading or the oxidation degree of the O-CD. At optimal conditions, the permeance increment was nearly double (from 9.2 to 21.1 Lm-2·h-1·bar-1). While the selectivity was without significant sacrifice, the rejection of PEG 200 remained around 90%. Meanwhile, the membrane stability was demonstrated by pro-longed filtratiing a PEG 200 aqueous solution. The constant permeance and rejection confirmed the O-CD-PEI/HPAN membranes were stable. The incorporation of activated CD in PEI offers a facile strategy to promote the permeance of PEI-based membranes.

A polyphenol and ε-polylysine functionalized bacterial cellulose/PVA multifunctional hydrogel for wound healing

Hydrogels for wound dressings have recently attracted considerable attention in the field of biomedical materials. Developing hydrogel dressings with multiple functions, including good antibacterial, mechanical and adhesive properties, to enhance wound regeneration is significant for clinical applications. To this end, a novel hydrogel wound dressing (PB-EPL/TA@BC) was developed, which was prepared by incorporating bacterial cellulose (BC) modified with tannic acid and ε-polylysine (EPL) into a PVA and borax matrix through a simple method without introducing any other chemical reagents. The hydrogel exhibited good adhesion (8.8 ± 0.2 kPa) to porcine skin, and the mechanical properties were significantly improved after adding BC. Meanwhile, it showed good inhibition against Escherichia coli, Staphylococcus aureus and Methicillin-resistant Staphylococcus aureus (84.1 ± 2.6 %, 86.0 ± 2.3 % and 80.7 ± 4.5 %) in vitro and Methicillin-resistant Staphylococcus aureus (MRSA) in vivo without the use of antibiotics, ensuring that the process of wound repair with a sterile environment. The hydrogel also presented good cytocompatibility and biocompatibility and could achieve hemostasis within 120 s. The in vivo experiments indicated that hydrogel could not only instantly complete hemostasis of the injured liver models but also obviously promote wound healing in a full-thickness skin. Furthermore, the hydrogel accelerated wound healing process by reducing inflammation promoting collagen deposition compared with commercial Tegaderm™ films. Therefore, the hydrogel is a promising high-end dressing material for wound hemostasis and repair for to enhance the wound healing.

Lyotropic Liquid Crystal (LLC)-Templated Nanofiltration Membranes by Precisely Administering LLC/Substrate Interfacial Structure

Mesoporous materials based on lyotropic liquid crystal templates with precisely defined and flexible nanostructures offer an alluring solution to the age-old challenge of water scarcity. In contrast, polyamide (PA)-based thin-film composite (TFC) membranes have long been hailed as the state of the art in desalination. They grapple with a common trade-off between permeability and selectivity. However, the tides are turning as these novel materials, with pore sizes ranging from 0.2 to 5 nm, take center stage as highly coveted active layers in TFC membranes. With the ability to regulate water transport and influence the formation of the active layer, the middle porous substrate of TFC membranes becomes an essential player in unlocking their true potential. This review delves deep into the recent advancements in fabricating active layers using lyotropic liquid crystal templates on porous substrates. It meticulously analyzes the retention of the liquid crystal phase structure, explores the membrane fabrication processes, and evaluates the water filtration performance. Additionally, it presents an exhaustive comparison between the effects of substrates on both polyamide and lyotropic liquid crystal template top layer-based TFC membranes, covering crucial aspects such as surface pore structures, hydrophilicity, and heterogeneity. To push the boundaries even further, the review explores a diverse array of promising strategies for surface modification and interlayer introduction, all aimed at achieving an ideal substrate surface design. Moreover, it delves into the realm of cutting-edge techniques for detecting and unraveling the intricate interfacial structures between the lyotropic liquid crystal and the substrate. This review is a passport to unravel the enigmatic world of lyotropic liquid crystal-templated TFC membranes and their transformative role in global water challenges.

Preparation and Lithium-Ion Separation Property of ZIF-8 Membrane with Excellent Flexibility

Metal-organic framework (MOF) membranes exhibit immense potential for separation applications due to their regular pore channels and scalable pore sizes. However, structuring a flexible and high-quality MOF membrane remains a challenge due to its brittleness, which severely restricts its practical application. This paper presents a simple and effective method in which continuous, uniform, defect-free ZIF-8 film layers of tunable thickness are constructed on the surface of inert microporous polypropylene membranes (MPPM). To provide heterogeneous nucleation sites for ZIF-8 growth, an extensive amount of hydroxyl and amine groups were introduced on the MPPM surface using the dopamine-assisted co-deposition technique. Subsequently, ZIF-8 crystals were grown in-situ on the MPPM surface using the solvothermal method. The resultant ZIF-8/MPPM exhibited a lithium-ion permeation flux of 0.151 mol m^-2 h^-1 and a high selectivity of Li⁺/Na⁺ = 1.93, Li⁺/Mg²⁺ = 11.50. Notably, ZIF-8/MPPM has good flexibility, and the lithium-ion permeation flux and selectivity remain unchanged at a bending curvature of 348 m^-1. These excellent mechanical characteristics are crucial for the practical applications of MOF membranes.

Enhancing Physiochemical Substrate Properties of Thin-Film Composite Membranes for Water and Wastewater Treatment via Engineered Osmosis Process

The commercial thin-film composite (TFC) nanofiltration (NF) membrane is unsuitable for engineered osmosis processes because of its thick non-woven fabric and semi-hydrophilic substrate that could lead to severe internal concentration polarization (ICP). Hence, we fabricated a new type of NF-like TFC membrane using a hydrophilic coated polyacrylonitrile/polyphenylsulfone (PAN/PPSU) substrate in the absence of non-woven fabric, aiming to improve membrane performance for water and wastewater treatment via the engineered osmosis process. Our results showed that the substrate made of a PAN/PPSU weight ratio of 1:5 could produce the TFC membrane with the highest water flux and divalent salt rejection compared to the membranes made of different PAN/PPSU substrates owing to the relatively good compatibility between PAN and PPSU at this ratio. The water flux of the TFC membrane was further improved without compromising salt rejection upon the introduction of a hydrophilic polydopamine (PDA) coating layer containing 0.5 g/L of graphene oxide (PDA/GO0.5) onto the bottom surface of the substrate. When tested using aerobically treated palm oil mill effluent (AT-POME) as a feed solution and 4 M MgCl2 as a draw solution, the best performing TFC membrane with the hydrophilic coating layer achieved a 67% and 41% higher forward osmosis (FO) and pressure retarded osmosis (PRO) water flux, respectively, compared to the TFC membrane without the coating layer. More importantly, the coated TFC membrane attained a very high color rejection (>97%) during AT-POME treatment, while its water flux and reverse solute flux were even better compared to the commercial NF90 and NF270 membranes. The promising outcomes were attributed to the excellent properties of the PAN/PPSU substrate that was coated with a hydrophilic PDA/GO coating and the elimination of the thick non-woven fabric during TFC membrane fabrication.

Felix D, Yeh HH, Luo HD, Moskalev I, Wang Q, Wang R, Grecov D, Fazli L, Lange D, Kizhakkedathu JN. Robust Nanoparticle-Derived Lubricious Antibiofilm Coating for Difficult-to-Coat Medical Devices with Intricate Geometry

A major medical device-associated complication is the biofilm-related infection post-implantation. One promising approach to prevent this is to coat already commercialized medical devices with effective antibiofilm materials. However, developing a robust high-performance antibiofilm coating on devices with a nonflat geometry remains unmet. Here, we report the development of a facile scalable nanoparticle-based antibiofilm silver composite coating with long-term activity applicable to virtually any objects including difficult-to-coat commercially available medical devices utilizing a catecholic organic-aqueous mixture. Using a screening approach, we have identified a combination of the organic-aqueous buffer mixture which alters polycatecholamine synthesis, nanoparticle formation, and stabilization, resulting in controlled deposition of in situ formed composite silver nanoparticles in the presence of an ultra-high-molecular-weight hydrophilic polymer on diverse objects irrespective of its geometry and chemistry. Methanol-mediated synthesis of polymer-silver composite nanoparticles resulted in a biocompatible lubricious coating with high mechanical durability, long-term silver release (∼90 days), complete inhibition of bacterial adhesion, and excellent killing activity against a diverse range of bacteria over the long term. Coated catheters retained their excellent activity even after exposure to harsh mechanical challenges (rubbing, twisting, and stretching) and storage conditions (>3 months stirring in water). We confirmed its excellent bacteria-killing efficacy (>99.999%) against difficult-to-kill bacteria (Proteus mirabilis) and high biocompatibility using percutaneous catheter infection mice and subcutaneous implant rat models, respectively, in vivo. The developed coating approach opens a new avenue to transform clinically used medical devices (e.g., urinary catheters) to highly infection-resistant devices to prevent and treat implant/device-associated infections.

A charged nanocomposite membrane via co-deposition of gallic acid and polyethyleneimine-silver for improving separation and antibacterial properties

Pharmaceuticals have been continuously detected from surface water and groundwater. In order to improve the rejection performance of pharmaceuticals by a nanofiltration membrane (NF), a positively charged membrane was prepared by co-deposition of natural gallic acid and polyethyleneimine on the polyacrylonitrile hydrolysis membrane. Effects of gallic acid concentration, polyethylene imine concentration, reaction time, and the molecular weight of polyethylene imine were documented. The physical and chemical properties of the membrane were also investigated by surface morphology, hydrophilicity, surface charge, and molecular weight cut-off. The optimized membrane had a molecular weight cut-off of about 958 Da and possessed a pure water permeability of 74.21 L·m^-2·h^-1·MPa^-1. The results exhibited salt rejection in the following order: MgCl₂ > CaCl₂ > MgSO₄ > Na₂CO₃ > NaCl > Na₂SO₄, while the rejection ability of pharmaceuticals is as follows: amlodipine > atenolol > carbamazepine > ibuprofen, suggesting that the positively charged membrane has enhanced retention to both divalent cations and charged pharmaceuticals. In addition, the antibacterial membrane was obtained by loading silver nanoparticles onto the positively charged membrane, which greatly improved the antibacterial ability of the membrane.

Metal-Polyphenol Coordination at the Aqueous Contra-diffusion "Interface": A Green Way to High-Performance Iron(III)/Tannic Acid Thin-Film-Composite Nanofiltration Membranes

Thin-film-composite (TFC) nanofiltration membranes have found wide uses in environment remediation and industrial separation. There is a growing trend to avoid the use of organic solvents and toxic chemicals during membrane fabrication. Therefore, the aqueous fabrication of TFC membranes receives considerable interest as a green and sustainable process. However, it remains challenging to construct a defect-free and ultrathin film in a homogeneous aqueous phase without the assistance of an interface. The contra-diffusion process provides a special "interface" to confine the film formation within a narrow space by regulating the competition between precursor diffusion and interfacial reactions. Herein, Fe³⁺/tannic acid (TA) TFC membranes were fabricated by a contra-diffusion process. The effects of fabrication parameters on the Fe³⁺/TA TFC membrane microstructure and performance were also investigated. The negatively charged membrane performs a competitive Na₂SO₄ rejection of 95.6% with a permeation flux of 44.3 L m^-2 h^-1 under 0.6 MPa as well as more than 99.5% rejection to several anionic dyes. The as-prepared membranes perform superior nanofiltration performance compared to other reported Fe³⁺/TA-based membranes, owing to the thin and defect-free selective layers by self-regulation. Moreover, the membranes exhibit stable rejection during a long-term nanofiltration test.

Rapid Immobilization of Silver Nanoparticles via Amino-quinone Coatings Enables Surface-Enhanced Raman Scattering Detection

Immobilization of metal nanoparticles (NPs) on flexible substrates for surface-enhanced Raman scattering (SERS) has received great attention. Anchoring NPs on substrates generally involves the process of surface modification, thanks to its simple, universal, and nondestructive features. 2-Hydroxy-1,4-naphthoquinone (HNQ), a plant-derived compound used to dye hairs and nails, may interact with polyamine or metal ions to form a surface coating. Here, we report the formation of amino-quinone coatings via the co-deposition of HNQ and polyethyleneimine, which provides a functionalized platform to rapidly immobilize Ag NPs on substrates such as a poly(dimethylsiloxane) (PDMS) film to fabricate Ag-PDMS substrates for SERS detection. The detection concentrations are down to 10^-8 M for rhodamine 6G. This work expands the system of surface co-deposition and further provides a facile route to prepare a highly efficient SERS substrate.

Development and Investigation of Hierarchically Structured Thin-Film Nanocomposite Membranes from Polyamide/Chitosan Succinate Embedded with a Metal-Organic Framework (Fe-BTC) for Pervaporation

Thin-film composite membranes (TFC) obtained by the formation of a selective layer on a porous membrane-substrate via interfacial polymerization (IP) are indispensable for separation procedures in reverse osmosis, nanofiltration, pervaporation, and gas separation. Achieving high selectivity and permeability for TFC membranes is still one of the main challenges in membrane science and technology. This study focuses on the development of thin film nanocomposite (TFN) membranes with a hierarchically structured polyamide (PA)/chitosan succinate (ChS) selective layer embedded with a metal-organic framework of iron 1,3,5-benzenetricarboxylate (Fe-BTC) for the enhanced pervaporation dehydration of isopropanol. The aim of this work was to study the effect of Fe-BTC incorporation into the ChS interlayer and PA selective layer, obtained via IP, on the structure, properties, and performance of pervaporation TFN membranes. The structure and hydrophilicity of the developed TFN membranes were investigated using scanning electron microscopy (SEM) and atomic force microscopy (AFM), along with water contact angle measurements. The developed TFN membranes were studied in the pervaporation dehydration of isopropanol (12-30 wt % water). It was found that incorporation of Fe-BTC into the ChS interlayer yielded the formation of a smoother, more uniform, and defect-free PA ultrathin selective layer via IP, due to the amorpho-crystalline structure of particles serving as the amine storage reservoir and led to an increase in membrane selectivity toward water, and a slight decrease in permeation flux compared to the ChS interlayered TFC membranes. The best pervaporation performance was demonstrated by the TFN membrane with a ChS-Fe-BTC interlayer and the addition of 0.03 wt % Fe-BTC in the PA layer, yielding a permeation flux of 197-826 g·m^-2·h^-1 and 98.50-99.99 wt % water in the permeate, in the pervaporation separation of isopropanol/water mixtures (12-30 wt % water).

Fabrication of ZnO/y-FeOOH nanoparticles embedded on the polyethylene terephthalate membrane: Evaluation of antifouling behavior and COD removal

Nanofiltration contributes to the development of advanced treatment of wastewater. An antifouling mixed matrix recycled polyethylene terephthalate (rPET) membrane modified by the hydrophilic ZnO/y-FeOOH nanoparticles (NPs) was fabricated via the electrospinning method. The effect of ZnO/y-FeOOH NP_S embedded in rPET as a modifier on the fabrication of nanocomposite membranes was investigated regarding water flux, membrane morphology, permeability, fouling resistance, and COD removal. The surface morphology of the rPET-ZnO/y-FeOOH membrane was evaluated by field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), water contact angle (WCA), and porosity and pore structure.Due to the embedding of NPs, the resulting rPET-ZnO/y-FeOOH membrane, with a low WCA of 53.404° angle, conforms significantly improved hydrophilicity and water permeation flux. The FESEM image displayed the distribution of cuboidal and needle-like ZnO and FeOOH NPs on the rPET membrane. The performance of the nanofiltration system related to the removal efficiency of COD was studied. It was deduced that the rPET-ZnO/y-FeOOH membrane had a superior COD removal capability (95.7%) at a pressure of 2 bar. Protein rejection tests were performed on antifouling behavior. The nanocomposite membrane with a high antifouling capability was related to 0.5 wt·% ZnO/y-FeOOH NPs (flux recovery ratio [FRR] = 96.2%, R_r = 90.21%, and R_ir = 3.001%). The modification procedure in this study (as a great improving technique) was proposed to fabricate the antifouling nanofiltration membrane.

Preparation of composite polyethersulfone membrane containing basalt powder and optimization of the parameters using response surface methodology

In this study, environmental-friendly composite polyethersulfone (PES) membranes based on basalt powder were prepared by phase inversion method. The effects of polymer percentage, the basalt percentage, and the thickness of the membrane were investigated on the distilled water flux, compaction factor, bovine serum albumin (BSA) rejection, contact angle, fouling factor and the parameters were modelled by response surface methodology (RSM). The distilled water flux increased when the basalt was added to the membrane up to 6% percentage of the polymer amount. The blending of basalt also provided resistance against the membrane compaction. The BSA rejection experiments approved the positive effects of basalt on the rejections efficiencies. At higher basalt percentages, the rejection efficiencies increased from 78% at the raw membrane to 99% for the composite membranes had 10% basalt. The adding of basalt to the membranes decreased the contact angles. The hydrophilicity of the membranes contained basalt in their structures was higher than those which had not basalt. By comparison with the neat membranes and the basalt added membrane, it can be said that the basalt increased the flux recovery and decreased the irreversible fouling factors. The basalt increased the antifouling properties for the composite membranes. Finally, the prepared membranes were characterized by scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX).

Progress for Co-Incorporation of Polydopamine and Nanoparticles for Improving Membranes Performance

Incorporating polydopamine has become a viable method for membrane modification due to its universality and versatility. Fillers in their different categories have been confirmed as effective elements to improve the properties of membranes such as hydrophilicity, permeability, mechanical strength, and fouling resistance. Thus, this paper mainly highlights the recent studies that have been carried out using polydopamine and nanomaterial fillers simultaneously in modifying the performance of different membranes such as ultrafiltration, microfiltration, nanofiltration, reverse osmosis, and forward osmosis membranes according to the various modification methods. Graphene oxide nanoparticles have recently attracted a lot of attention among different nanoparticles used with polydopamine, due to their impressive characteristics impacts on enhancing membrane hydrophilicity, mechanical strength, and fouling resistance. Thus, the incorporation techniques of graphene oxide nanoparticles and polydopamine for enhancing membranes have been highlighted in this work. Moreover, different studies carried out on using polydopamine as a nanofiller for optimizing membrane performance have been discussed. Finally, perspectives, and possible paths of further research on mussel-inspired polydopamine and nanoparticles co-incorporation are stated according to the progress made in this field. It is anticipated that this review would provide benefits for the scientific community in designing a new generation of polymeric membranes for the treatment of different feed water and wastewater based on adhesive mussel inspired polydopamine polymer and nanomaterials combinations.

Durable Surfaces from Film-Forming Silver Assemblies for Long-Term Zero Bacterial Adhesion without Toxicity

The long-term prevention of biofilm formation on the surface of indwelling medical devices remains a challenge. Silver has been reutilized in recent years for combating biofilm formation due to its indisputable bactericidal potency; however, the toxicity, low stability, and short-term activity of the current silver coatings have limited their use. Here, we report the development of silver-based film-forming antibacterial engineered (SAFE) assemblies for the generation of durable lubricous antibiofilm surface long-term activity without silver toxicity that was applicable to diverse materials via a highly scalable dip/spray/solution-skinning process. The SAFE coating was obtained through a large-scale screening, resulting in effective incorporation of silver nanoparticles (∼10 nm) into a stable nonsticky coating with high surface hierarchy and coverage, which guaranteed sustained silver release. The lead coating showed zero bacterial adhesion over a 1 month experiment in the presence of a high load of diverse bacteria, including difficult-to-kill and stone-forming strains. The SAFE coating showed high biocompatibility and excellent antibiofilm activity in vivo.

A high stability GO nanofiltration membrane preparation by co-deposition and crosslinking polydopamine for rejecting dyes

In order to improve the stability of nanofiltration membrane in separation and purification, a novel polyelectrolyte multilayer nanofiltration membrane was facilely prepared by co-deposition of polydopamine (PDA) and polyethyleneimine (PEI) on the polyethersulfone (PES) ultrafiltration membrane substrate, followed by immersing graphene oxide (GO) solution, and crosslinking PDA. The modified surfaces were characterized using scanning electron microscopy (SEM) and atomic force microscopy (AFM), water contact angle, their saline flux and ability to reject salt and dye were determined. The results also exhibited salt rejection ability as Na₂SO₄ > K₂SO₄ > MgSO₄ > NaCl > KCl > MgCl₂, suggesting the higher rejection of divalent anion. Also, the retention order of the dye by the GO modified membrane is DY86 > DB19 > AG27 > DY142 > DB56 > AR151 > VB5, indicating that the GO modified membrane has better rejection of negatively charged dyes as well as higher molecular weight dyes. Ethanol and hypochlorite resistance tests under different pH conditions showed the membranes coated GO enhanced stability in regard to salt rejection properties. Significantly, the anti-biological test confirmed the growth rate of microalgae on the GO introduced membrane was decreased greatly due to enhanced stability and lower roughness.

Dopamine-Supported Metallization of Polyolefins─A Contribution to Transfer to an Eco-friendly and Efficient Technological Process

Metallization is a common method to produce functional or decorative coatings on plastic surfaces. State-of-the-art technologies require energy-intensive process steps and the use of organic solvents or hazardous substances to achieve sufficient adhesion between the polymer and the metal layer. The present study introduces a facile bio-inspired "green" approach to improve this technology: the use of dopamine, a small-molecule mimic of the main structural component of adhesive mussel proteins, as an adhesion promoter. To understand dopamine adhesion and identify conditions for successful metallization, polyethylene surfaces were dip-coated with dopamine and metallized with nickel by electroless metallization; essential parameters such as temperature, pH value, concentration of dopamine and buffer, and the deposition time were systematically varied. Effects of adding oxidants to the dopamine bath, cross-linking, thermal and UV post-treatment of the polydopamine film, and plasma pretreatment of the substrate were investigated. The properties of the polydopamine layer and the quality of the metal film were studied by physico-chemical, optical, and mechanical techniques. It was shown that simple dip-coating of the substrate with dopamine under optimal conditions is sufficient to support metal layers with a good optical quality. Technologically relevant metal layer quality and adhesion were obtained with annealed and UV-treated polydopamine films and enhanced by plasma pretreatment of the substrate. The study shows that dopamine provides a new interfacial design for plastic metallization that can reduce energy consumption, use of hazardous substances, and reject rate during manufacturing. The results are essential findings for further technological developments of a universal platform to promote adhesion between plastics and metal or potentially also other material classes, enabling economic material development and more eco-friendly applications.

Hybrid hydrogels derived from renewable resources as a smart stimuli responsive soft material for drug delivery applications

The design and synthesis of amphiphilic molecules play a crucial role in fabricating smart functional materials via self-assembly. Especially, biologically significant natural molecules and their structural analogues have inspired chemists and made a major contribution to the development of advanced smart materials. In this report, a series of amphiphilic N-acyl amides were synthesized from natural precursors using a simple synthetic protocol. Interestingly, the self-assembly of amphiphiles 6a and 7a furnished a hydrogel and oleogel in vegetable oils. Morphological analysis of gels revealed the existence of a 3-dimensional fibrous network. Thermoresponsive and thixotropic behavior of these gels were evaluated using rheological analysis. A composite gel prepared by the encapsulation of curcumin in the hydrogel formed from 7a displayed a gel-sol transition in response to pH and could act as a dual channel responsive drug carrier.

Design of microstructure for hollow fiber loose nanofiltration separation layer and its compactness-tailoring mechanism

In order to promote the application of membrane technology in the treatment of textile wastewater containing small molecule dye, fabricating a hollow fiber loose nanofiltration (LNF) with a thin and compact separation layer and deepening the understanding of compactness-tailoring mechanism in chemical crosslinking are essential. Firstly, the mechanisms of synergistic crosslinking of PEI-70K and PEI-10K, along with a weakening of the PEI hydration by ethanol, were expounded in primary crosslinking. Then, some LNF separation layers with different compactness were prepared through crosslinking with different crosslinkers to further reduce pore size, which resulted in the efficient removal (~100%) of a small molecular dye (methyl orange (MO), M = 327 g mol^-1). The removal of methyl orange is mainly caused by size sieving. The relationship among the pore size, the M_w of the secondary crosslinkers, and the pore size reduction rate was interpreted by comparing the pore size reduction rate of three secondary crosslinkers with different molecular weights. In addition, the as-prepared separation layer exhibited excellent dimensional stability and solvent resistance. This paper not only provides a reference for fabricating hollow fiber LNF with better purification performance, but also shows their potential in developing solvent resistant nanofiltration.

Tailored design of nanofiltration membranes for water treatment based on synthesis-property-performance relationships

Tailored design of high-performance nanofiltration (NF) membranes is desirable because the requirements for membrane performance, particularly ion/salt rejection and selectivity, differ among the various applications of NF technology ranging from drinking water production to resource mining. However, this customization greatly relies on a comprehensive understanding of the influence of membrane fabrication methods and conditions on membrane properties and the relationships between the membrane structural and physicochemical properties and membrane performance. Since the inception of NF, much progress has been made in forming the foundation of tailored design of NF membranes and the underlying governing principles. This progress includes theories regarding NF mass transfer and solute rejection, further exploitation of the classical interfacial polymerization technique, and development of novel materials and membrane fabrication methods. In this critical review, we first summarize the progress made in controllable design of NF membrane properties in recent years from the perspective of optimizing interfacial polymerization techniques and adopting new manufacturing processes and materials. We then discuss the property-performance relationships based on solvent/solute mass transfer theories and mathematical models, and draw conclusions on membrane structural and physicochemical parameter regulation by modifying the fabrication process to improve membrane separation performance. Next, existing and potential applications of these NF membranes in water treatment processes are systematically discussed according to the different separation requirements. Finally, we point out the prospects and challenges of tailored design of NF membranes for water treatment applications. This review bridges the long-existing gaps between the pressing demand for suitable NF membranes from the industrial community and the surge of publications by the scientific community in recent years.