Fabrication of polyetherimide nanocomposite membrane with amine functionalised halloysite nanotubes for effective removal of cationic dye effluents

Fabrication of 2D Vanadium MXene Polyphenylsulfone Ultrafiltration Membrane for Enhancing the Water Flux and for Effective Separation of Humic Acid and Dyes from Wastewater

MXene, a new 2D transition metal carbide-based material, is gaining outstanding attention in recent days in the area of separation and purification. In this study, we have successfully synthesized vanadium-based MXene-V2CT x (where T represents functional groups such as -OH, O, and F) by etching an aluminum layer from V2AlC. For the first time, a vanadium-based MXene-V2CT x -embedded mixed matrix membrane was fabricated and utilized for removal of hazardous dye and humic acid from wastewater. With an increase in V2CT x loading, the hydrophilicity of the polyphenylsulfone (PPSU) membrane reasonably improved, and its water contact angle was reduced from 82.8 to 70.9°. V2CT x nanosheet-embedded PPSU membrane exhibited an excellent pure water permeability of 247 L m-2 h-1, which was 266% elevated than the pristine PPSU membrane. The V2CT x -PPSU membrane revealed a good antifouling nature, thermal stability, and 98.5% removal of humic acid. The optimal membrane exhibited 96.6 and 82.02% expulsion of Reactive Black 5 (RB 5) dye and Reactive Orange 16 (RO 16) dye, respectively. The flux for RO 16 and RB 5 dyes and humic acid were remarkable with a value of 202.02, 161.61, and 141.41 L m-2 h-1, respectively. This work provides a new V2CT x -incorporated PPSU ultrafiltration membrane to effectively treat humic acid and dye wastewater.

Synthesis, Characterization, and Evaluation of the Adsorption Behavior of Cellulose-Graft-Poly(Acrylonitrile-co-Acrylic Acid) and Cellulose-Graft-Poly(Acrylonitrile-co-Styrene) towards Ni(II) and Cu(II) Heavy Metals

In this study, the synthesis and characterization of grafted cellulose fiber with binary monomers mixture obtained using a KMnO4/citric acid redox initiator were investigated. Acrylonitrile (AN) was graft copolymerized with acrylic acid (AA) and styrene (Sty) at different monomer ratios with evaluating percent graft yield (GY%). Cell-g-P(AN-co-AA) and Cell-g-P(AN-co-Sty) were characterized by SEM, FT-IR, 13C CP MAS NMR, TGA, and XRD. An AN monomer was used as principle-acceptor monomer, and GY% increases with AN ratio up to 60% of total monomers mixture volume. The adsorption behaviors of Cell-g-P(AN-co-AA) and Cell-g-P(AN-co-Sty) were studied for the adsorption of Ni(II) and Cu(II) metal ions from aqueous solution. Optimal adsorption conditions were determined, including 8 h contact time, temperature of 30 °C, and pH 5.5. Cell-g-P(AN-co-AA) showed maximum adsorption capacity of 435.07 mg/g and 375.48 mg/g for Ni(II) and Cu(II), respectively, whereas Cell-g-P(AN-co-Sty) showed a maximum adsorption capacity of 379.2 mg/g and 349.68 mg/g for Ni(II) and Cu(II), respectively. Additionally, adsorption equilibrium isotherms were studied, and the results were consistent with the Langmuir model. The Langmuir model's high determinant coefficient (R2) predicted monolayer sorption of metal ions. Consequently, Cell-g-P(AN-co-AA) and Cell-g-P(AN-co-Sty) prepared by a KMnO4/citric acid initiator were found to be efficient adsorbents for heavy metals from wastewater as an affordable and adequate alternative.

Halloysite Nanotube-Enhanced Polyacrylonitrile Ultrafiltration Membranes: Fabrication, Characterization, and Performance Evaluation

This research focuses on the production and characterization of pristine polyacrylonitrile (PAN) as well as halloysite nanotube (HNT)-doped PAN ultrafiltration (UF) membranes via the phase inversion technique. Membranes containing 0.1, 0.5, and 1% wt HNT in 16% wt PAN are fabricated, and their chemical compositions are examined using Fourier transform infrared (FTIR) spectroscopy. Scanning electron microscopy (SEM) is utilized to characterize the membranes' surface and cross-sectional morphologies. Atomic force microscopy (AFM) is employed to assess the roughness of the PAN/HNT membrane. Thermal characterization is conducted using thermal gravimetric analysis (TGA) and differential thermal analysis (DTA), while contact angle and water content measurements reveal the hydrophilic/hydrophobic properties. The pure water flux (PWF) performance of the porous UF water filtration membranes is evaluated at 3 bar, with porosity and mean pore size calculations. The iron (Fe), manganese (Mn), and total organic carbon (TOC) removal efficiencies of PAN/HNT membranes from dam water are examined, and the surfaces of fouled membranes are investigated by using SEM post-treatment. Mechanical characterization encompasses tensile testing, the Mori-Tanaka homogenization approach, and finite element analysis. The findings offer valuable insights into the impact of HNT doping on PAN membrane characteristics and performance, which will inform future membrane development initiatives.

Removing of cationic dyes using self-cleaning membranes-based PVC/nano-cellulose combined with titanium aluminate

This research used the phase inversion approach to construct polyvinyl chloride nanocellulose@titanium aluminate nanocomposite membranes (PVC/NC@TALCM) to adsorb and filter dye from wastewater. FTIR, XRD, and SEM were used to determine the adsorptive nanocomposite membrane that had been synthesized. The thermal and electrical properties measurements were carried out using a static system. The influence of several adsorbent dosages, pH, and dye concentrations on the nanocomposite membrane's adsorption ability was investigated. Using a dead-end filtration system, the PVC-NC@TALCM was evaluated as a pressure filtration membrane system. It was found that 98.6% of MB dye was removed by PVC-NC@TALCM membrane, which was loaded with 5% titanium aluminate at pH 10. The kinetic adsorption studies indicated that the adsorption of MB onto the PVC-NC@TALCM nanocomposite membrane obeys pseudo-second-order that indicates the chemosorption process. The isotherm data were described using Freundlich and Langmuir models, and the Freundlich isotherms were shown to be more closely match the experimental data than the Langmuir model. Finally, the PVC-NC@TALCM nanocomposite membrane was economical, environmentally friendly, and self-cleaning.

Fabrication of electrospun polyamide–weathered basalt nano-composite as a non-conventional membrane for basic and acid dye removal

Abstract

In this study, an adsorptive electrospun polyamide membrane (ESPA) and electrospun polyamide–weathered basalt composite membrane (ESPA-WB) were prepared by an electrospinning process at room temperature. Hence, the WB structure was built as a polymeric membrane separation film in combination with the ESPA matrix as a composite nano-filtration membrane. Then, the ESPA and ESPA-WB membranes were characterized using BET surface area analysis, Fourier transform infrared spectroscopy, X-ray diffraction, and scanning electron microscopy (SEM). To avoid cracks forming during the sintering process, the WB should be added in certain percentages. The microstructures of the prepared membranes were investigated to evaluate their efficiency for basic and acidic dyesʼ removal and their permeation flux. Compared with the ESPA, the ESPA-WB membrane combines the characteristics of WB and ESPA, which greatly enhances the performance of both methylene blue (MB) and methyl orange (MO) dyes removal from synthetic wastewater. The outcomes of this study indicated that the dye uptake in the case of ESPA-WB is higher than that of ESPA, and it decreases with an increase in dye concentrations. The obtained membrane ESPA-WB showed both an excellent anti-dye fouling and a good rejection property for both dyes (i.e. 90% rejection for MB and 74% for MO) with no sign of contamination by the applied dyes. It was found that the structure of the ESPA-WB membrane contains a large number of several adsorption sites which leads to an increase in the removal rate of dyes. Hence, this study demonstrated a non-conventional strategy to prepare an effective adsorptive nano-composite membrane that can be applied as a highly recyclable one for the removal of organic dyes.

Graphic abstract

"Jianbing" styling multifunctional electrospinning composite membranes for wound healing

Wound infection and excessive exudate can affect the process of wound healing. However, the disadvantage of the anti-microbial wound dressings is that the biological fluids are ineffectively removed. Inspired by making "Chinese Jianbing", a composite wound nano-dressing was developed consisting of a hydrophilic outer layer (chitosan&polyvinyl alcohol: CTS-PVA) and a hydrophobic inner layer (propolis&polycaprolactone: PRO-PCL) by combining casting and electrospinning methods for effective antibacterial and unidirectional removing excess biofluids. In vitro, the composite wound nano-dressing of PRO-PCL and CTS-PVA (PPCP) could strongly inhibit Pseudomonas aeruginosa. Furthermore, PPCP wound dressing had excellent antioxidant properties and blood coagulation index for effective hemostatic. Importantly, it had a preferable water absorption for removing excess biofluid. In vivo, it had anti-inflammatory properties and promoted collagen Ⅰ preparation, which realized 80% wound healing on day 7. In short, the PPCP wound dressing provides a new direction and option for antibacterial and removes excess biofluid.

Development of Antifouling Thin-Film Composite/Nanocomposite Membranes for Removal of Phosphate and Malachite Green Dye

Nowadays polymer-based thin film nanocomposite (TFN) membrane technologies are showing key interest to improve the separation properties. TFN membranes are well known in diverse fields but developing highly improved TFN membranes for the removal of low concentration solutions is the main challenge for the researchers. Application of functional nanomaterials, incorporated in TFN membranes provides better performance as permeance and selectivity. The polymer membrane-based separation process plays an important role in the chemical industry for the isolation of products and recovery of different important types of reactants. Due to the reduction in investment, less operating costs and safety issues membrane methods are mainly used for the separation process. Membranes do good separation of dyes and ions, yet their separation efficiency is challenged when the impurity is in low concentration. Herewith, we have developed, UiO-66-NH₂ incorporated TFN membranes through interfacial polymerization between piperazine (PIP) and trimesoyl chloride (TMC) for separating malachite green dye and phosphate from water in their low concentration. A comparative study between thin-film composite (TFC) and TFN has been carried out to comprehend the benefit of loading nanoparticles. To provide mechanical strength to the polyamide layer ultra-porous polysulfone support was made through phase inversion. As a result, outstanding separation values of malachite green (MG) 91.90 ± 3% rejection with 13.32 ± 0.6 Lm^-2h^-1 flux and phosphate 78.36 ± 3% rejection with 22.22 ± 1.1 Lm^-2h^-1 flux by TFN membrane were obtained. The antifouling tendency of the membranes was examined by using bovine serum albumin (BSA)-mixed feed and deionized water, the study showed a good ~84% antifouling tendency of TFN membrane with a small ~14% irreversible fouling. Membrane's antibacterial test against E. coli. and S. aureus. also revealed that the TFN membrane possesses antibacterial activity as well. We believe that the present work is an approach to obtaining good results from the membranes under tricky conditions.

QSAR model and mechanism research on color removal efficiency of dying wastewater by FeCl3 coagulation

Coagulation is the most widely used method in the treatment of printing and dying wastewater. To better understand the relationship between the coagulation effect and dye molecular structures, quantitative structure activity relationship (QSAR) analyses were performed to elucidate the factors affecting the coagulation in ferric chloride (FeCl₃) coagulation process. First, the coagulation experiments on 38 dye molecules were conducted to determine their color removal rates (R_exp) by FeCl₃ under different pH conditions (i.e., pH = 4 and 10). The results showed that the average R_exp of dyes were 41.36% ± 2.40% at pH value of 4 and 55.70% ± 2.83% at pH value of 10. Subsequently, a multiple linear regression (MLR) method was used to construct QSAR models based on R_exp and 42 molecular parameters calculated by Gaussian 09, Materials Studio 7.0 and Multiwfn. The developed QSAR models exhibited excellent stability, reliability, and robustness with values of R² = 0.7950, 0.8170, Q²_INT = 0.6401, 0.7382, Q²_EXT = 0.5168, 0.5441, at pH values of 4 and 10, respectively. Through analysis of quantum parameter values, electrostatic adsorption and hydrogen bonding adsorption were primarily responsible for the coagulation process. Therefore, this study could be useful in providing critical information for evaluating the removal efficiency and a feasible way to predict the removal rate of dyes by FeCl₃ when no coagulation experiments were conducted.

Absolute film separation of dyes/salts and emulsions with a superhigh water permeance through graded nanofluidic channels

The development of multifunctional films with a high permeability has been of great concern for effective separation of complex aqueous contaminants, especially in the face of zero or near-zero release regulations. Inspired by the natural structure of sandy soils, polydopamine-wrapped/connected polypyrrole sub-micron spheres (PPSM) were closely packed onto a polypyrrole-coated bacterial cellulose (PBC) support, by which a new two-layered PBC/PPSM composite film formed with graded nanofluidic channels. Interestingly, after being soaked in complex water environments of ethanol, acids, bases, heat, cold and high salinity, or else bended/folded for more than 10 times, the structure and performance of this film still stayed the same, validating its high structural stability and flexibility. Even in a high salinity environment over seawater, this PBC/PPSM film exhibits a dye-separation capacity of almost 100% with a surprisingly superhigh water permeance over one thousand L h^-1 m^-2 bar^-1, one or two magnitudes higher than that of the related films reported in the literature. Meanwhile, the ability for effective oil-water-separation was also validated. Besides the superhydrophilicity and underwater superoleophobicity, the synapse-like-structure-induced graded nanofluidic channels are also proposed to play a key role for rendering such an outstandingly comprehensive performance of the film by greatly overcoming fluid resistance and reducing permeation viscosity.

Facile fabrication of a low-cost and environmentally friendly inorganic-organic composite membrane for aquatic dye removal

This study reports a new inorganic-organic composite membrane fabricated by an electrostatic self-assembling method. The low-cost and eco-friendly porous geopolymer (PG) was chosen as a support, on which chitosan (CS), a "green" biomaterial, was used to form an active layer. With optimum dosage of CS (2.0 mL of 1.0% CS solution), the obtained CS/PG membrane exhibited a high porosity of 50.97% with an average pore diameter of 13.93 nm as well as a high water flux of 1663.82 ± 22.46 L/m²·h·bar. The effects of initial concentration, pH, flow rate and temperature of the feed solution on crystal violet (CV) removal by the CS/PG were evaluated in a continuous mode. The results indicated ~95% CV could be removed from water during continuous treating of 14 h. The effectiveness in CV removal by the CS/PG membrane was attributed to the synergistic effect of rejection and adsorption. Furthermore, the composite membrane could be easily regenerated for prolonged use. Overall, this work opens a new possibility of building cost-saving and eco-friendly composite membranes for practical applications in water purification.

Polysulfone Membranes Embedded with Halloysites Nanotubes: Preparation and Properties

In the present study, nanocomposite ultrafiltration membranes were prepared by incorporating nanotubes clay halloysite (HNTs) into polysulfone (PSF) and PSF/polyvinylpyrrolidone (PVP) dope solutions followed by membrane casting using phase inversion method. Characterization of HNTs were conducted using scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and thermogravimetric (TGA) analysis. The pore structure, morphology, hydrophilicity and mechanical properties of the composite membranes were characterized by using SEM, water contact angle (WCA) measurements, and dynamic mechanical analysis. It was shown that the incorporation of HNTs enhanced hydrophilicity and mechanical properties of the prepared PSF membranes. Compared to the pristine PSF membrane, results show that the total porosity and pore size of PSF/HNTs composite membranes increased when HNTs loadings were more than 0.5 wt % and 1.0 wt %, respectively. These findings correlate well with changes in water flux of the prepared membranes. It was observed that HNTs were homogenously dispersed within the PSF membrane matrix at HNTs content of 0.1 to 0.5 wt % and the PSF/HNTs membranes prepared by incorporating 0.2 wt % HNTs loading possess the optimal mechanical properties in terms of elastic modulus and yield stress. In the case of the PSF/PVP matrix, the optimal mechanical properties were obtained with 0.3 wt % of HNTs because PVP enhances the HNTs distribution. Results of bovine serum albumin (BSA) filtration tests indicated that PSF/0.2 wt % HNTs membrane exhibited high BSA rejection and notable anti-fouling properties.

Investigations on the Properties and Performance of Mixed-Matrix Polyethersulfone Membranes Modified with Halloysite Nanotubes

Ultrafiltration (UF) polyethersulfone (PES) membranes were prepared by wet phase inversion method. Commercial halloysite nanotubes (HNTs) in the amount of 0.5–4 wt % vs PES (15 wt %) were introduced into the casting solution containing the polymer and N,N-dimethylformamide as a solvent. The morphology, physicochemical properties and performance of the membranes were characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM), zeta potential, porosity and contact angle analyses, as well as permeability measurements. Moreover, the antifouling properties of the membranes were evaluated during UF of a model solution of bovine serum albumin (BSA). The research revealed a positive influence of modification with HNTs on hydrophilicity, water permeability and antifouling properties of the PES membranes. The most significant improvement of permeability was obtained in case of the membrane containing 2 wt % of HNTs, whereas the highest fouling resistance was observed for 0.5 wt % HNTs content. It was found that a good dispersion of HNTs can be obtained only at loadings below 2 wt %. Based on the results a relation between severity of membrane fouling and surface roughness was proved. Moreover, an increase of the roughness of the modified membranes was found to be accompanied by an increase of isoelectric point values.

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.