Improved performance of polyamide thin-film composite nanofiltration membrane by using polyetersulfone/polyaniline membrane as the substrate

Synthesis of the Ag2S/PANI@PES Composite Membrane and Its Antipollution Properties

Membrane separation technology offers a sustainable and efficient solution to wastewater management; however, membrane fouling significantly impedes its application. Photocatalytic membranes, integrating photocatalytic and membrane separation technologies, enhance membrane separation efficacy while effectively mitigating organic and biological contaminations. In this work, Ag2S/PANI@PES composite membranes were prepared via a facile in situ polymerization and successive layer adsorption technique. The modified poly(ether sulfone) (PES) membrane demonstrated improved hydrophilicity and separation performance, and its heterostructure between polyaniline (PANI), Ag0, and Ag2S effectively addressed organic fouling issues. Moreover, Ag2S/PANI@PES exhibited outstanding antimicrobial properties, as well as chemical and mechanical stability.

Recent advances in cellulose- and alginate-based hydrogels for water and wastewater treatment: A review

From the environmental perspective, it is essential to develop cheap, eco-friendly, and highly efficient materials for water and wastewater treatment. In this regard, hydrogels and hydrogel-based composites have been widely employed to mitigate global water pollution as this methodology is simple and free from harmful by-products. Notably, alginate and cellulose, which are natural carbohydrate polymers, have gained great attention for their availability, price competitiveness, excellent biodegradability, biocompatibility, hydrophilicity, and superior physicochemical performance in water treatment. This review outlined the recent progress in developing and applying alginate- and cellulose-based hydrogels to remove various pollutants such as dyes, heavy metals, oils, pharmaceutical contaminants, and pesticides from wastewater streams. This review also highlighted the effects of various physical or chemical methods, such as crosslinking, grafting, the addition of fillers, nanoparticle incorporation, and polymer blending, on the physiochemical and adsorption properties of hydrogels. In addition, this review covered the alginate- and cellulose-based hydrogels' current limitations such as low mechanical performance and poor stability, while presenting strategies to improve the drawbacks of the hydrogels. Lastly, we discussed the prospects and future directions of alginate- and cellulose-based hydrogels. We hope this review provides valuable insights into the efficient preparations and applications of hydrogels.

High-Performance Novel Polyoxometalate-LDH Nanocomposite-Modified Thin-Film Nanocomposite Forward Osmosis Membranes: A Study of Desalination and Antifouling Performance

Numerous investigations have focused on creating effective membranes for desalination in order to alleviate the water scarcity crisis. In this study, first, LDH nanoplates were synthesized and utilized to alter the surface of thin-film composite (TFC) membranes in the course of this investigation. Following that, a simple technique was used to produce a novel nanocomposite incorporating LDH layers and Na14(P2W18Co4O70)·28H2O polyoxometalate nanoparticles, resulting in the creation of a fresh variety of thin-film nanocomposite (TFN). The performance of all of the membranes acquired was examined in the process of forward osmosis (FO). The impact of the compounds that were prepared was assessed on the hydrophilicity, topology, chemical structure, and morphology of the active layer of polyamide (PA) through analysis methods such as atomic force microscopy (AFM), energy-dispersive X-ray (EDX), FTIR spectroscopy, powder X-ray diffraction (XRD), scanning electron microscopy (SEM), and water contact angle (WCA) goniometry. After evaluating the outcomes of both modified membrane types, it was observed that the membrane equipped with the nanocomposite modifier at a concentration of 0.01 wt % exhibited the highest water flux, measuring 46.6 LMH and selectivity of 0.23 g/L. This membrane was thus considered the best option. Furthermore, the membrane's ability to prevent fouling was examined, and the findings revealed an enhancement in its resistance to fouling in comparison to the filler-free membrane.

Design of an Antibiotic-Releasing Polymer: Physicochemical Characterization and Drug Release Patterns

Conventional drug delivery has its share of shortcomings, especially its rapid drug release with a relatively short duration of therapeutic drug concentrations, even in topical applications. Prolonged drug release can be effectively achieved by modifying the carrier in a drug delivery system. Among the several candidates for carriers studied over the years, poly (ether ether ketone), a biocompatible thermoplastic, was chosen as a suitable carrier. Its inherent hydrophobicity was overcome by controlled sulfonation, which introduced polar sulfonate groups onto the polymer backbone. Optimization of the sulfonation process was completed by the variation of the duration, temperature of the sulfonation, and concentration of sulfuric acid. The sulfonation was confirmed by EDS and the degree of sulfonation was determined by an NMR analysis (61.6% and 98.9%). Various physical properties such as morphology, mechanical strength, and thermal stability were studied using scanning electron microscopy, tensile testing, and thermogravimetric analysis. Cytotoxicity tests were performed on the SPEEK samples to study the variation in biocompatibility against a Vero cell line. The drug release kinetics of ciprofloxacin (CP) and nalidixic acid sodium salt (NA)-loaded membranes were studied in deionized water as well as SBF and compared against the absorbance of standardized solutions of the drug. The data were then used to determine the diffusion, distribution, and permeability coefficients. Various mathematical models were used to fit the obtained data to establish the order and mechanism of drug release. Studies revealed that drug release occurs by diffusion and follows zero-order kinetics.

Novel polyaniline-polyethersulfone nanofiltration membranes: effect of in situ polymerization time on structure and desalination performance

In this research, novel polyaniline-layered nanofiltration membranes were prepared by phase inversion of base polyethersulfone (PES) membranes and subsequent in situ solution-phase deposition of polyaniline as a thin surface layer. In these composite membranes, the impact of the polyaniline deposition time on steric hindrance and electrostatic interactions during permeation was elucidated. The chemical structure, thermal stability, and mechanical properties of the PES and PANI-PES membranes were investigated using Fourier-transform infrared spectroscopy (ATR-FTIR), thermogravimetric analysis (TGA), and dynamic mechanical analysis (DMA), respectively. The membranes' porosity and pore size decreased as PANI deposition time increased. As PANI deposition time increased, PANI layered nanofiltration membranes exhibited improved thermal stability but deteriorated mechanical characteristics due to free radical destruction from prolonged exposure to the oxidant. These PANI-PES membranes showed 43% rejection (NaCl) at 1.7 bar coupled with a flux of 11.59 L h-1 m2 that is quite promising when comparing with similar Nanofilteration (NF) membranes in the literature and commercial NF membranes, as well. As the deposited layer, PANI is partially doped; hence, permeation results have been interpreted in terms of steric hindrance and electrostatic repulsion by electrochemical PANI layering.

High Flux Nanofiltration Membranes with Double-Walled Carbon Nanotube (DWCNT) as the Interlayer

Nanofiltration (NF) membranes with a high permeability and rejection are of great interest in desalination, separation and purification. However, how to improve the permeation and separation performance still poses a great challenge in the preparation of NF membranes. Herein, the novel composite NF membrane was prepared through the interfacial polymerization of M-phenylenediamine (MPD) and trimesoyl chloride (TMC) on a double-walled carbon nanotube (DWCNT) interlayer supported by PES substrate. The DWCNT interlayer had a great impact on the polyamide layer formation. With the increase of the DWCNT dosage, the XPS results revealed an increase in the number of carboxyl groups, which decreased the crosslinking degree of the polyamide layer. Additionally, the AFM results showed that the surface roughness and specific surface area increased gradually. The water flux of the prepared membrane increased from 25.4 L/(m²·h) and 26.6 L/(m²·h) to 109 L/(m²·h) and 104.3 L/(m²·h) with 2000 ppm Na₂SO₄ and NaCl solution, respectively, under 0.5 MPa. Meanwhile, the rejection of Na₂SO₄ and NaCl decreased from 99.88% and 99.38% to 96.48% and 60.47%. The proposed method provides a novel insight into the rational design of the multifunctional interlayer, which shows great potential in the preparation of high-performance membranes.

Effect of the Incorporation of ZIF-8@GO into the Thin-Film Membrane on Salt Rejection and BSA Fouling

A series of Zeolitic imidazole framework-8 (ZIF-8) clusters supported on graphene oxide (ZIF-8@GO) nanocomposites were prepared by varying the ratios of ZIF-8 to GO. The resultant nanocomposites were characterized using various techniques, such as Scanning Electron Microscope (SEM), Transmission Electron Microscope (TEM), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), thermogravimetric analysis (TGA), Fourier Transform Infrared (FTIR) and Raman spectroscopy. These nanocomposites were incorporated into the thin film layer during interfacial polymerisation process of m-phenylenediamine (aqueous phase which contained the dispersed nanocomposites) and trimesoyl chloride (TMC, organic phase) at room temperature onto polyethersulfone (PES) ultrafiltration (UF) support membrane. The membrane surface morphology, cross section and surface roughness were characterized using SEM and AFM, respectively. Compared to the baseline membranes, the thin film nanofiltration (TFN) membranes exhibited improved pure water flux (from 1.66 up to 7.9 L.m^-2h^-1), salt rejection (from 40 to 98%) and fouling resistance (33 to 88%). Optimum ZIF-8 to GO ratio was established as indicated in observed pure water flux, salt rejection and BSA fouling resistance. Therefore, a balance in hydrophilic and porous effect of the filler was observed to lead to this observed membrane behaviour suggesting that careful filler design can result in performance gain for thin film composite (TFC) membranes for water treatment application.

Thin-film nanocomposite NF membrane with GO on macroporous hollow fiber ceramic substrate for efficient heavy metals removal

The ceramic membrane has been widely used in the wastewater treatment based on the chemical resistance and superior separation performance. A robust and defect-free thin-film nanocomposite (TFN) nanofiltration (NF) membrane on the macroporous hollow fiber ceramic (HFC) substrate was novelly developed for heavy metals removal. Before interfacial polymerization (IP), the aqueous solution of graphene oxide (GO) grafted with ethylenediamine (EDA) was deposited on the HFC substrate by vacuum filtration. Then, a thin polyamide (PA) film was fabricated by EDA and 1,3,5-trimesoyl chloride (TMC), followed by heat treatment. The effects of GO content and EDA concentration on the performance of the NF membrane have been systematically investigated. The results showed that when the GO content was 0.015 mg·mL^-1 and the EDA concentration was 0.75 wt.%, the as-prepared eGO₃/PA-HFC membrane had a rejection rate of 94.12% for MgCl₂ and a pure water flux of 18.03 L·m^-2·h^-1. Additionally, the removal ability of eGO₃/PA-HFC membranes for heavy metal ions was satisfactory (93.33%, 92.73%, 90.45% and 88.35% for Zn²⁺, Cu²⁺, Ni²⁺ and Pb²⁺, respectively). The study explored further that it was efficient and stable for heavy metal ions removal during 30 h in the simulated tap water and mining wastewater, which indicated that the eGO/PA-HFC membrane has great application potential in wastewater treatment.

Development of high-performance mixed matrix reverse osmosis membranes by incorporating aminosilane-modified hydrotalcite

Thin film nanocomposite (TFN) reverse osmosis (RO) membranes were prepared by dispersing 3-aminopropyltriethoxysilane (APTES) modified hydrotalcite (HT), designated as A-HT, in aqueous solution and incorporating the nanoparticles in polyamide layers during the interfacial polymerization process. Results of Fourier transform infrared spectroscopy and zeta potential characterization showed the successful modification of nanoparticles by APTES. In addition, Fourier transform infrared spectroscopy suggested that amidation would take place between the aminosilane on APTES and trimesoyl chloride in organic solution, providing firm covalent interaction between the nanoparticles and polyamide matrix. Dynamic light scattering and transmission electron microscopy indicated that aminosilane modification improved dispersibility of the nanoparticles in aqueous solution and obtained membranes, which suppressed the aggregation. Both the covalent interaction and aggregation suppression were beneficial to compatibility between nanoparticles and the polyamide matrix. TFN RO membranes incorporated with A-HT demonstrated excellent performance. Compared with the pristine RO membrane, the water flux of A-HT-0.050 prepared with an optimum A-HT concentration of 0.050 wt% was enhanced by 18.6% without sacrificing the salt rejection. Moreover, the selectivity of A-HT-0.050 was superior to that of HT-0.050 prepared with HT of 0.050 wt%, which proved aminosilane modification of hydrotalcite was beneficial to high membrane performance especially to selectivity.

Thin film nanocomposite reverse osmosis membranes were prepared by dispersing 3-aminopropyltriethoxysilane modified hydrotalcite in aqueous solution and incorporating the nanoparticles in polyamide layer during interfacial polymerization process.

Direct grafting of tetraaniline via perfluorophenylazide photochemistry to create antifouling, low bio-adhesion surfaces

Conjugated polyaniline has shown anticorrosive, hydrophilic, antibacterial, pH-responsive, and pseudocapacitive properties making it of interest in many fields. However, in situ grafting of polyaniline without harsh chemical treatments is challenging. In this study, we report a simple, fast, and non-destructive surface modification method for grafting tetraaniline (TANI), the smallest conjugated repeat unit of polyaniline, onto several materials via perfluorophenylazide photochemistry. The new materials are characterized by nuclear magnetic resonance (NMR) and electrospray ionization (ESI) mass spectroscopy. TANI is shown to be covalently bonded to important carbon materials including graphite, carbon nanotubes (CNTs), and reduced graphene oxide (rGO), as confirmed by transmission electron microscopy (TEM). Furthermore, large area modifications on polyethylene terephthalate (PET) films through dip-coating or spray-coating demonstrate the potential applicability in biomedical applications where high transparency, patternability, and low bio-adhesion are needed. Another important application is preventing biofouling in membranes for water purification. Here we report the first oligoaniline grafted water filtration membranes by modifying commercially available polyethersulfone (PES) ultrafiltration (UF) membranes. The modified membranes are hydrophilic as demonstrated by captive bubble experiments and exhibit extraordinarily low bovine serum albumin (BSA) and Escherichia coli adhesions. Superior membrane performance in terms of flux, BSA rejection and flux recovery after biofouling are demonstrated using a cross-flow system and dead-end cells, showing excellent fouling resistance produced by the in situ modification.