Polyethersulfone ultrafiltration membrane incorporated with ferric-based metal-organic framework for textile wastewater treatment

Microplastics and dye removal from textile wastewater using MIL-53 (Fe) metal-organic framework-based ultrafiltration membranes

Microplastics (MPs) and other organic matters in textile wastewater have posed a formidable challenge for treatment processes, particularly in the primary stages such as ultrafiltration (UF). UF plays a crucial role in preventing the entry of pollutants into subsequent treatment steps. However, the performance efficiency of UF membranes is compromised by the potential fouling of membrane pores by MPs, dyes and other organic pollutants such as bovine serum albumin (BSA). This study focuses on enhancing UF membrane performance, specifically its antifouling properties, through the development of high-performance membranes using MIL-53(Fe) metal-organic framework (MOF) particles (noted as MIL-53 here). Various concentrations of the MIL-53 (0.05, 0.1, 0.2, and 0.5 wt%) were integrated into the membrane structure through phase inversion process. Streaming zeta potential results confirmed the negatively charged surface of the membranes and their high hydrophilicity was validated through contact angle analysis. FTIR, SEM, EDS, and XRD confirmed the presence of MIL-53 particles on the surface of membranes. The developed membranes were tested for 24 h to assess their antifouling properties, with a subsequent 30-min hydraulic flush to measure their flux recovery ratios. Methylene Blue (MB) dye was used as a cationic dye present in textile wastewater to evaluate the efficiency of the developed membranes in dye removal and the synergistic effects of dye rejection in the presence of organic matters (i.e., MPs and BSA). Since previous studies have not fully addressed the combination of dyes and organic matter, this study thoroughly investigated the effect of particle-type foulants (MPs) and their interactions with dye (MB), as well as water soluble protein-type foulants (BSA) and their interaction with MB. The results indicated that the developed membranes exhibited higher MB rejection when the dye was present with either MP or BSA, along with improved antifouling properties. The optimised UF membrane integrated with 0.1 wt% MIL-53 demonstrated nearly 96% BSA rejection and around 86% MB rejection in the mixed foulant case (BSA-MB). The modified membrane exhibited a substantial increase in water flux from 176 L m-2.h-1 to 327 L m-2.h-1. The findings of this research show the potential of iron-based MOFs in improving the performance of UF membranes and provide a platform for future studies on significant areas such as long-term stability studies and testing with other pollutants found in textile wastewater.

Graphene-modified MIL-125-NH2 mixed matrix membranes for efficient H2 and CH4 purification

This study investigates the performance of the mixed matrix membranes (MMMs) incorporating hybrid fillers of metal-organic framework (MIL-125-NH2) and graphene nanosheets (GNs) for enhanced methane (CH₄) and hydrogen (H₂) separation in the purification sector. The physico-chemical properties of the MMMs were evaluated by SEM, XRD, FTIR, AFM, TGA, DTG, and Brunauer-Emmett-Teller. The permeability and selectivity of the MMMs were determined using different single gases (CO2, N2, H2, and CH4) at various temperatures (20-60 °C). Optimization of fabrication parameters resulted in a significant improvement in porosity and roughness of the fabricated MMMs. The permeabilities of the MOF/PES membrane are 20.3 (CO2), 23.9 (N2), 32.2 (CH4), and 24.1 (H2) x 104 Barrer, while incorporating 0.05 wt% of GNs into the MOF/PES membrane improved the permeability by 36 % (CO2), 41 % (N2), 31 % (CH4), and 370 % (H2). In addition, the H2/CO2 and H2/N2 selectivities of the MMMs significantly increased up to 4 and 3.3, with an improvements of 236 % and 230 %, respectively, compared to the MOF/PES membrane. Furthermore, the CH4/CO2 and CH4/N2 selectivities of the MMMs decreased by 4 %. Therefore, a hybrid filler (10 wt % of MIL-125-NH2 and 0.05 wt % of GNs is highly recommended to improve the permeability and selectivity of the PES membrane, expanding its potential applications in CH4 and H2 purification.

Construction of a multi-layer protection of CS polymer brush grafted DA@CNTs coating on PVDF membrane for effective removal of dye effluent

In the process of removing dye wastewater, the membrane surface is susceptible to contamination, resulting in reduced performance and limited dye separation efficiency. A single hydrophilic modification layer is not enough to achieve effective separation of different types of dyes. The present research designed a "double layer protection" method in order to overcome the above deficiencies. A solution of dopamine (DA) coated carbon nanotubes (CNTs-COOH) was covered on the surface of the polyvinylidene fluoride (PVDF) membrane by deposition, followed by grafting a layer of chitosan (CS) polymer brushes on its surface. The spatial double layer structure provides an excellent barrier effect and effectively reduces the contamination of dyes. When filtering different types of dyes, effective filtration of anionic and cationic dyes through the electrostatic effect of the first layer, the adsorption of CNTs in the second layer and the hydration layer of both layers. All membranes have excellent rejection properties. More importantly, the membranes also had good chemical and mechanical stability and their serviceability was not degraded. Therefore, the prepared PVDF-based multi-layer composite membranes behave a potential application prospect in the wastewater purification field.

Fluorine-Containing, Self-Assembled Graft Copolymer for Tuning the Hydrophilicity and Antifouling Properties of PVDF Ultrafiltration Membranes

Neat poly(vinylidene fluoride) (PVDF) ultrafiltration (UF) membranes exhibit poor water permeance and surface hydrophobicity, resulting in poor antifouling properties. Herein, we report the synthesis of a fluorine-containing amphiphilic graft copolymer, poly(2,2,2-trifluoroethyl methacrylate)-g-poly(ethylene glycol) behenyl ether methacrylate (PTFEMA-g-PEGBEM), hereafter referred to as PTF, and its effect on the structure, morphology, and properties of PVDF membranes. The PTF graft copolymer formed a self-assembled nanostructure with a size of 7-8 nm, benefiting from its amphiphilic nature and microphase separation ability. During the nonsolvent-induced phase separation (NIPS) process, the hydrophilic PEGBEM chains were preferentially oriented towards the membrane surface, whereas the superhydrophobic PTFEMA chains were confined in the hydrophobic PVDF matrix. The PTF graft copolymer not only increased the pore size and porosity but also significantly improved the surface hydrophilicity, flux recovery ratio (FRR), and antifouling properties of the membrane. The membrane performance was optimal at 5 wt.% PTF loading, with a water permeance of 45 L m-2 h-1 bar-1, a BSA rejection of 98.6%, and an FRR of 83.0%, which were much greater than those of the neat PVDF membrane. Notably, the tensile strength of the membrane reached 6.34 MPa, which indicated much better mechanical properties than those reported in the literature. These results highlight the effectiveness of surface modification via the rational design of polymer additives and the precise adjustment of the components for preparing membranes with high performance and excellent mechanical properties.

Designing a novel poly (methyl vinyl ether maleic anhydride) based polymeric membrane with enhanced antifouling performance for removal of pentachlorophenol from aqueous solution

In this current study, poly (methyl vinyl ether maleic anhydride) (PMVEAMA), a sustainable additive, was incorporated into poly (ether-ether sulfone) (PEES) polymer to design a novel polymeric hybrid membrane for the efficient filtration of toxic pentachlorophenol (PCP) from an aqueous medium. Hydrophilic additives significantly altered the membrane's morphology, structure, porosity, water content, and flux performance compared to the bare PEES membrane. The influence of PMVEAMA on the structural modification of the synthesized polymer membrane was confirmed by SEM, ATR-FTIR, XRD, AFM, zeta potential and contact angle. Findings revealed that the addition of PMVEAMA to the PEES polymer enhances the porosity (17.7%-28.9%), water content (29.8%-39.8%), and pure water flux (186 Lm^-2h^-1 to 349 Lm^-2h^-1). The effect of PMVEAMA concentration on the PEES membrane exhibited more finger like pores, better porosity and hydrophilicity, reduced surface roughness, fouling and increased permeability. The fouling studies exhibit an improved 57% PCP rejection and permeation flux of 22.3 Lm^-2h^-1 due to the addition of the hydrophilic additive. Surprisingly, the incorporation of PMVEAMA into the bare PEES membrane resulted in a high flux recovery ratio of 73.7%. The antifouling properties and enhanced permeability of the PEES/PMVEAMA membrane indicates its potential application in water purification sectors for the efficient separation of contaminants.

Incorporation of 2D-biotene to polyethersulfone ultrafiltration membrane with superhydrophilicity and antifouling properties for removal of organic pollutants

Here, for the first time, one or few-layer exfoliated 2D-Biotene (E-BIT) was prepared by a cost-effective liquid-phase exfoliation of economical and accessible bulk biotite (B-BIT). The successful preparation of E-BIT was further verified by different characterization methods. XRD pattern demonstrated that B-BIT's basal spacing was increased from 10.07 Å to 11.02 Å. Also, the transparency of the E-BIT to the electron beam showed its small thickness after exfoliation, which was confirmed by AFM results, too. This natural material was utilized as an efficient nano-additive to improve the properties of polyethersulfone (PES) polymeric membrane. E-BIT blended membranes with various quantities (0-2 wt%) were prepared via the non-solvent induced phase inversion method. Small holes at the up layer, coarse finger-like holes and macro-voids at the sublayer were seen in asymmetric prepared membranes. Modification caused the improvement of the membranes' hydrophilicity, which the contact angle was reduced from 69.3 to 53.4 for bare PES and 1 wt% E-BIT blended membranes, respectively. 1 wt% E-BIT blended membrane illustrated flux enhancement of 198.8 L/m² h, and high elimination efficiency of bovine serum albumin (99%), reactive red 195 (97.8%), reactive green 9 (93.5%), and reactive blue 19 (88.4%), with improved flux recovery ratio of 73%.

Fabrication and Investigation of Acid Functionalized CNT Blended Nanocomposite Hollow Fiber Membrane for High Filtration and Antifouling Performance in Ultrafiltration Process

In this study, we fabricated a nanocomposite polyethersulfone (PES) HF membrane by blending acid functionalized carbon nanotubes (FCNT) to address the issue of reduced membrane life, increased energy consumption, and operating costs due to low permeability and membrane fouling in the ultrafiltration process. Additionally, we investigated the effect of FCNT blending on the membrane in terms of the physicochemical properties of the membrane and the filtration and antifouling performance. The FCNT/PES nanocomposite HF membrane exhibited increased water permeance from 110.1 to 194.3 LMH/bar without sacrificing rejection performance and increased the flux recovery ratio from 89.0 to 95.4%, compared to a pristine PES HF membrane. This study successfully developed a high filtration and antifouling polymer-based HF membrane by blending FCNT. Furthermore, it was validated that blending FCNT into the membrane enhances the filtration and antifouling performance in the ultrafiltration process.

Converting recycled membranes into photocatalytic membranes using greener TiO2-GRAPHENE oxide nanomaterials

Despite the widespread use of membrane separation processes for water treatment, operation costs and fouling still restrict their application. Costs can be overcome by recycled membranes whereas fouling can be mitigated by membrane modification. In this work, the performance of recycled reverse osmosis membranes modified by greener titanium dioxide (TiO₂) and graphene oxide (GO) in different modification routes were investigated and compared. The use of recycled membranes as a support acted more than a strategy for costs reduction, but also as an alternative for solid waste reduction. Low adhesion of nanoparticulate materials to the membrane surfaces were verified in depositions by self-assembly, whereas filtration and modification with dopamine generated membranes with well adhered and homogeneous layers. Considering the stability, permeability, and rejection efficiency of dyes as model substrates, the membranes modified with the aid of dopamine-TiO₂-GO were the most promising. The nanomaterials increased the membrane hydrophilicity and formed a hydrated layer that repels the organic contaminants and reduces fouling. Besides membrane rejection, adsorption (contribution: ∼10%) and photocatalysis (contribution: ∼20%) were additional mechanisms for pollutants removal by the modified membranes. The photocatalytic membrane modified with dopamine-TiO₂-GO was furthermore evaluated for the removal of six different pharmaceutical active compounds (PhACs), noticing gains in terms of removal efficiency (up to 95.7%) and fouling mitigation for the modified membrane compared to the original membranes. The photocatalytic activity still contributed to a simultaneous degradation of PhACs avoiding the generation of a concentrated stream for further disposal.

Enhanced Methylene Blue Adsorption by Cu-BTC Metal-Organic Frameworks with Engineered Particle Size Using Surfactant Modulators

Metal–organic frameworks (MOFs) featuring porous structures and large specific surface areas have shown great potential in removing organic pollutants from wastewater via adsorption processes. Although the particle size of MOFs determines the adsorption performance (something known as the size-dependent effect), engineering it into desirable dimensions for enhancing the adsorption performance is a great challenge. Here, we develop a practical and facile approach to regulate the particle size of copper benzene-1,3,5-tricarboxylate (Cu-BTC) adsorbents with high tunability by screening the functional modulator of various surfactants adding in hydrothermal synthesis procedure. The effect of surfactant type and concentration on the particle size of Cu-BTC was systematically investigated. The results show that the nonionic surfactant polyvinylpyrrolidone (PVP) demonstrated the greatest ability to control the particle size of Cu-BTC among other counterparts (e.g., N, N, N-trimethyl-1-dodecanaminium bromide (DTAB), polyethylene glycol (PEG1000), sodium dodecyl sulfate (SDS), sodium dodecyl benzene sulfonate (SDBS) and hexadecyl trimethyl ammonium bromide (CTAB)). By increasing the PVP concentration to 0.14 mmol L−1, the average particle size of Cu-BTC could be correspondingly reduced by more than ten times, reaching to a comparative smaller value of 2.4 μm as compared with the reported counterparts. In addition, the PVP allowed a large increase of the surface area of Cu-BTC according to porosity analysis, resulting in a great enhancement of methylene blue (MB) adsorption. The PVP-modulated Cu-BTC showed fast adsorption kinetics for MB removal accompanied with a maximum adsorption capacity of 169.2 mg g−1, which was considerably competitive with most of the analogs reported. Therefore, our study may inspire concepts for engineering the particle size of Cu-BTCs with improved properties for more practical applications.

Polymer Nanocomposite Membrane for Wastewater Treatment: A Critical Review

With regard to global concerns, such as water scarcity and aquatic pollution from industries and domestic activities, membrane-based filtration for wastewater treatment has shown promising results in terms of water purification. Filtration by polymeric membranes is highly efficient in separating contaminants; however, such membranes have limited applications. Nanocomposite membranes, which are formed by adding nanofillers to polymeric membrane matrices, can enhance the filtration process. Considerable attention has been given to nanofillers, which include carbon-based nanoparticles and metal/metal oxide nanoparticles. In this review, we first examined the current status of membrane technologies for water filtration, polymeric nanocomposite membranes, and their applications. Additionally, we highlight the challenges faced in water treatment in developing countries.

Synchronous Engineering for Biomimetic Murray Porous Membranes Using Isocyanate

Highly permselective and durable membranes are desirable for massive separation applications. However, currently most membranes prepared using nonsolvent-induced phase separation (NIPS) suffer from low permeability and a high fouling tendency due to the great challenges in a rational design and also practical approach for membrane optimization. Inspired by the natural Murray network from vascular plants, we developed a hierarchical membrane via a straightforward yet robust strategy, using isocyanate as a multifunctional additive. Thanks to the integrated functions of a phase separation regulator, blowing agent, cross-linker, and functionalization anchor of isocyanate, our strategy is featured as a perfect combination of a phase separation and chemical reaction, and it enables synchronous engineering of the membrane hierarchy on porosity and components. The representative membrane exhibits superior water permeance (334 L/m²·h·bar), protein retention (>98%), and antifouling ability (flux recover ratio ∼ 98%). This work highlights a versatile path for pursuing a highly enhanced performance of NIPS-made membranes, from the fancy perspective of Murray bionics.

One-Step Water-Induced Phase Separation Simultaneously Triggering Polymer Solidification and Polyelectrolyte Complexation for Porous Ultrafiltration Membranes

Functional additives have been widely utilized for the membrane structure modulation and performance improvement during the nonsolvent-induced phase separation process, but the resulted membranes easily suffer from additives' inhomogeneous dispersity and compatibility with the polymer matrix. Herein, a facile and robust strategy, i.e., one-step water-induced phase separation, was proposed for the preparation of polyelectrolytes-contained composite membranes. Polyanion (dopamine modified polyacrylic acid) and polycation (quaternized chitosan paired with bis(trifluoromethane-sulfonyl)imide) were first premixed in dimethyl sulfoxide and used as polyelectrolyte additives in a polysulfone (PSF) solution, and then a uniform PSF-based casting solution was readily obtained. During the solvent-water exchange process, polymer solidification and polyelectrolyte complexation were simultaneously triggered, in situ generating a polyelectrolyte complex fixed within the membrane matrix. Ultrafiltration membranes with hierarchical structures were notably tailored through altering the concentration, molecular weight, and type of polyelectrolytes. The obtained membrane exhibited a water flux of 672 L·m^-2·h^-1, three times over the raw PSF membrane, while almost maintaining high bovine serum albumin (BSA) rejection. This work paves a straightforward and convenient path for the preparation of composite membranes with tunable architecture and properties.

Application of polysaccharide-based metal organic framework membranes in separation science

Polysaccharide/MOF composite membranes have captured the interests of many researchers during decontamination of polluted environments. Their popularity can be attributed to the relatively high chemical and thermal stabilities of these composite membranes. Chitosan is among the polysaccharides extensively used during the synthesis of hybrid membranes with MOFs. The applications of chitosan/MOF composite membranes in separation science are explored in detail in this paper. Researchers have also synthesised mixed matrix membranes of MOFs with cellulose and cyclodextrin that have proved to be effective during separation of a variety of materials. The uses of cellulose/MOF and cyclodextrin/MOF membranes for the removal of environmental pollutants are discussed in this review. In addition, the challenges associated with the use of these mixed matrix membranes are explored in this current paper.

Emerging Materials to Prepare Mixed Matrix Membranes for Pollutant Removal in Water

Various pollutants of different sizes are directly (e.g., water-borne diseases) and indirectly (e.g., accumulation via trophic transfer) threatening our water health and safety. To cope with this matter, multifaceted approaches are required for advanced wastewater treatment more efficiently. Wastewater treatment using mixed matrix membranes (MMMs) could provide an excellent alternative since it could play two roles in pollutant removal by covering adsorption and size exclusion of water contaminants simultaneously. This paper provides an overview of the research progresses and trends on the emerging materials used to prepare MMMs for pollutant removal from water in the recent five years. The transition of the research trend was investigated, and the most preferred materials to prepare MMMs were weighed up based on the research trend. Various application examples where each emerging material was used have been introduced along with specific mechanisms underlying how the better performance was realized. Lastly, the perspective section addresses how to further improve the removal efficiency of pollutants in an aqueous phase, where we could find a niche to spot new materials to develop environmentally friendly MMMs, and where we could further apply MMMs.