Membranes For Water Treatment Research Articles

Selective O2-to-H2O2 Electrosynthesis by a High-Performance, Single-Pass Electrofiltration System Using Ibuprofen-Laden CNT Membranes.

Producing H2O2 through a selective, two-electron (2e) oxygen reduction reaction (ORR) is challenging, especially when it serves as an advanced oxidation process (AOP) for cost-effective water decontamination. Herein, we attain a 2e-selectivity H2O2 production using a carbon nanotube electrified membrane with ibuprofen (IBU) molecules laden (IBU@CNT-EM) in an ultrafast, single-pass electrofiltration process. The IBU@CNT-EM can generate H2O2 at a rate of 25.62 mol gCNT-1 h-1 L-1 in the permeate with a residence time of 1.81 s. We demonstrated that an interwoven, hydrophilic-hydrophobic membrane nanostructure offers an excellent air-to-water transport platform for ORR acceleration. The electron transfer number of the ORR for IBU@CNT at neutral pH was confirmed as 2.71, elucidating a near-2e selectivity to H2O2. Density functional theory (DFT) studies validated an exceptional charge distribution of the IBU@CNT for the O2 adsorption. The adsorption energies of the O2 and *OOH intermediates are proportional to the H2O2 selectivity (64.39%), higher than that of the CNT (37.81%). With the simple and durable production of H2O2 by IBU@CNT-EM electrofiltration, the permeate can actuate Fenton oxidation to efficiently decompose emerging pollutants and inactivate bacteria. Our study introduces a new paradigm for developing high-performance H2O2-production membranes for water treatment by reusing environmental functional materials.

Superhydrophilic‐underwater superoleophobic polyvinyl alcohol membranes for oily water treatment

AbstractPolyvinyl alcohol (PVA) and potato starch‐based porous hydrogels have been fabricated and studied for their wettability. The starting material was crosslinked by glutaraldehyde performed via co‐polymerization reaction at room temperature and low temperature (freeze–thaw). The gels were characterized by Fourier transform infrared (FT‐IR), field emission scanning electron microscope (FE‐SEM), thermogravimetric (TG), and powder X‐ray diffraction (PXRD) analysis. The wetting studies of the gels were evaluated at ambient and submerged conditions by considering both oil and water drops as probe liquids. The gels tend to absorb oil and water in air, however, water‐wet gels demonstrated a very high oil contact angle (>150°). The gels demonstrated superoleophobicity, and the underwater oil CA >172° as the concentration (wt%) of PVA was increased in the gels. Overall, the freeze–thaw gels demonstrated higher underwater oil CA, however, both (room temperature and freeze–thaw fabricated) gels demonstrated similar affinity for under‐oil–water absorption and separation. The hydrogel can retain water easily and thus remove water (even dye dissolved in water) with high separation efficiency and recyclability.

Fabrication and performance evaluation of polycarbonate/polyvinyl alcohol–titanium dioxide thin‐film nanocomposite membranes for water treatment

AbstractIn recent years, there has been growing interest in using polymer nanocomposite membranes as a more advanced method for removing pollutants from water and treating wastewater for various purposes. In this study, thin‐film nanocomposite (TFN) membranes of polycarbonate/polyvinyl alcohol–titanium dioxide thin‐film (PC/PVA–TiO2) were fabricated by dip‐coating a PC substrate in a PVA/TiO2 solution. Various methods, including attenuated total reflectance‐Fourier transform infrared (ATR‐FTIR) spectroscopy, field emission scanning electron microscopy (FE‐SEM), atomic force microscopy (AFM), and water contact angle were utilized to assess the structural characteristics of the produced membranes. The PC/PVA thin‐film composite (TFC) and PC/PVA–TiO2 TFN membranes were then examined in a submerged membrane system to evaluate their effectiveness in filtering humic acid (HA) under various vacuum transmembrane pressure (0.3 and 0.6 bar) condition. The FTIR‐ATR results confirmed the formation of the active layer of PVA/TiO2 nanoparticles (NPs). It was observed that adding 1 wt.% of TiO2 NPs to the active layer of PVA/TiO2 significantly enhanced the water contact angle from 77.5° for PC support to 55.3° for PC/PVA–TiO2 (0.1) TFN membranes. Furthermore, the FE‐SEM results confirmed the formation of an active layer of PVA/TiO2 with a thickness of 237.87 nm. The pure water flux increased from 101.64 L/m2h for the PC/PVA TFC membrane to 144.02 L/m2h and 199.09 L/m2h for the PC/PVA–TiO2 (0.05) and PC/PVA–TiO2 (0.1) TFN membranes, respectively. Also, the results revealed that at lower transmembrane pressure, all membranes showed higher value in HA removal as compared to when higher transmembrane pressure was used.

Regulating molecules/ions sieving channels of MXene-based membranes by edge-capping strategy

Regulating molecules/ions transport within two-dimensional (2D) sub-nanometer channels to achieve a higher separation efficiency is of considerable interest for MXene membranes in sustainable water treatment. Herein, sodium tripolyphosphate (STPP) was introduced into Ti3C2Tx nanosheets to construct a series of modified STPP-MXene membranes based on the edge-capping strategy. The critical role of edge-capping in modulating selective molecules/ions separation within 2D sub-nanometer channels was highlighted. The edge-capping method was demonstrated to moderately narrow the shoulder spacing between adjacent Ti3C2Tx nanosheets and impaired their positive electric field intensity. In addition, the DFT results showed that the cations exhibited a much lower relative energy with STPP-Ti3C2Tx (-0.0024 eV) compared to Ti3C2Tx nanosheets (-0.2092 eV), causing cations to permeate more readily through the STPP-MXene membrane. As a result, the appropriately designed and prepared STPP-MXene membrane demonstrated an excellent molecules/ions selectivity (CR/NaCl selectivity = 52.6, CR/Na2SO4 selectivity = 30.3), much higher than that of the pristine MXene membrane. Moreover, by protecting the Ti at the edges of Ti3C2Tx nanosheets, the STPP-MXene membrane retained its original two-dimensional structure to maintain a stable separation performance, even when exposed to a water environment for up to 60 days. In contrast, the pristine MXene membrane was completely oxidized due to its weak stability. This study provides a theoretical basis for the feasibility of edge-capping strategy as a broad modification alternative to design high-efficiency molecular/ionic sieving MXene membranes.

Fabrication of ultra-permeable membranes with antibiofouling capability by incorporating bifunctionalized zeolite

Poor water permeance and biofouling significantly limit the application of nanofiltration (NF) membranes in wastewater treatment and seawater desalination. Herein, bifunctionalized FAU-Ag-OH zeolites, featuring abundant hydroxyl groups and silver ions on their surface, were designed and incorporated into polyamide (PA) layer of a thin-film nanocomposite (TFN) membrane, effectively enhancing the antibiofouling properties and water permeance of membrane. The plentiful hydroxyl groups and well-dispersed silver ions on the bifunctionalized FAU-Ag-OH zeolites impart the membrane with more negative surface charge, increased hydrophilicity, and superior antibiofouling property. Additionally, the doped FAU-Ag-OH zeolites can retard the diffusion of piperazine during interfacial polymerization (IP) process and have improved chemical compatibility with polymers, which results in desirable membrane structure. Consequently, the optimal M–0.05 membrane containing FAU-Ag-OH zeolites exhibited a 2.3-fold increase in water permeance (18.8 ± 2.0 L m−2 h−1 bar−1) and enhanced antibiofouling ability (with antibacterial efficiency up to 95.4 % and flux recovery ratio up to 85 %) compared with the TFC membrane. The successful fabrication of such membrane with enhanced antibiofouling properties and enhanced water permeance is expected to promote the application of NF membranes in water treatment.

Construction of CS-SDAEM long-chain polysaccharide derivative on TA@CNTs coated PVDF membrane with effective oil-water emulsion purification and low contamination rate

Currently, the most effective way to improve the anti-fouling performance of water treatment separation membrane is to enhance the hydrophilicity of the membrane surface, but it can still cause contamination, leading to the occurrence of flux reduction. The construction of a strong hydration layer to resist wastewater contamination is still a challenging task. In this study, a defect-free hydration layer barrier was achieved by grafting chitosan polysaccharide derivatives (CS-SDAEM) on the membrane, which achieved in effective fouling prevention and low flux decline rate. A layer of tannic acid-coated carbon nanotubes (TA@CNTs) has been uniformly deposited on the commercial PVDF membrane so that the surface was rich in -COOH groups, providing sufficient reaction sites. These reactive groups facilitate the grafting of amphiphilic polymers onto the membrane. This modification strategy achieved in enhancing the antifouling performance. The modified membrane achieved low contamination rate with DR of 16.9 % for wastewater filtration, and the flux recovery rate was above 95 % with PWF of 1100 (L·m−2·h−1). The membrane had excellent anti-fouling performance, which provided a new route for the future development of water treatment membrane.

Dynamic Deposition of PDA on a Hollow Fiber Ceramic Membrane for Oily Water Treatment.

Ceramic membranes have been widely used in oil-water treatment; however, membrane fouling remains a challenge that must be addressed to improve the process feasibility. A thin layer of polydopamine (PDA) was dynamically deposited on the surface of the alumina hollow fiber membranes to reduce oil adhesion. The PDA-alumina membranes were characterized by using SEM-EDS, AFM, and water contact angle measurements. The performance of the modified membranes was evaluated using synthetic crude oil emulsions (100 mg·L-1) in a crossflow system. Membranes modified with PDA exhibited 97% oil rejection, and a stabilized permeate flux of 463 L·h-1·m-2 with a relative flux reduction of 60% and a flux recovery ratio of 75% was observed after cleaning, indicating lower oil adhesion and better fouling reversibility. The most predominant fouling mechanism for the modified membranes seems to be cake filtration because of the reduction in pore size due to the deposition of the PDA layer.

Activating peroxymonosulfate with MOF-derived NiO-NiCo2O4/titanium membrane for water treatment: A non-radical dominated oxidation mechanism

Traditional peroxymonosulfate (PMS) catalytic membranes dominated by radical pathways often face interference from complex components in water bodies. Herein, we employed a controlled electro-deposition technique to coat a Ni-Co metal–organic framework (MOF) precursor onto titanium hollow fiber membrane (THFM), followed by high-temperature calcination to synthesize a MOF-derived NiO-NiCo2O4/THFM (M−NNCO−THFM) PMS catalytic membrane. Then, the M−NNCO−THFM filtration integrated with PMS activation (MFPA process) for water treatment. Experimental results demonstrated that the M−NNCO−THFM MFPA process successfully achieved complete phenol (PE) removal via a non-radical-dominated degradation pathway, involving singlet oxygen (1O2) and electron transfer, while exhibiting wide pH adaptability and exceptional stability in complex water matrices. Mechanism analysis revealed that the electron transfer process was significantly enhanced by the MOF-derived heterojunction structure, which increased the flat-band potential from 0.39 eV to 0.56 eV, thereby facilitating efficient electron transfer for PE removal. The non-radical 1O2 pathway was primarily due to the cycling of metal valence states (Ni2+/Co3+), leading to the reduction of Co2+ and its reaction with PMS, resulting in the generation of reactive species. Furthermore, electrochemical measurements indicated that the M−NNCO−THFM exhibited lower charge transfer resistance and enhanced charge transfer efficiency compared to non-MOF-derived NNCO-THFM, corresponding to the superior catalytic performance and electrochemically active surface area of M−NNCO−THFM.

Phthalocyanine-enabled technologies for water treatment and disinfection strategies

Water treatment and disinfection are critical factors in ensuring a safe and sustainable water supply. Phthalocyanines (Pcs), a class of versatile and robust organic compounds, have garnered significant attention for their application in various water treatment processes. This review paper offers a groundbreaking investigation of Pc-enabled technologies within the domain of water treatment applications. The core aim of this review is to meticulously analyze the chemical and optical properties of Pcs, elucidate their photosensitization mechanism and establish the crucial connection between their chemical structure and photodynamic efficacy. The various modes of Pcs application in water treatment processes - whether in solution, immobilized, or integrated into water treatment membranes - emphasizing the strategies for their integration and effectiveness in disinfection and decontamination has also been extensively investigated. Moreover, it sheds light on the latest advancements and challenges in the field, providing valuable insights into future research for employing Pcs in environmentally sustainable water treatment methods.

Research Progress on Water Treatment Membranes based on New Photocatalytic Materials

Research Progress on Water Treatment Membranes based on New Photocatalytic Materials

Surface Grafting of Magnetic Carbon Nanotubes and Their Vertical Alignment in PVDF Asymmetric Ultrafiltration Membranes for Fast Nanochannel Construction

The application of carbon nanotubes (CNTs) in water treatment membranes can increase the permeability and selectivity of the membranes. However, traditional CNTs are usually affected by van der Waals forces, which makes them prone to agglomerate in polymer membranes, and their non-directional arrangement in the membranes limits their transport efficiency as water channels in the membranes. In this paper, a reversible addition-fragmentation chain transfer (RAFT) polymerization method was used to synthesize propargyl methacrylate - random copolymerization - poly (ethylene glycol) methacrylate - block - polymethyl methacrylate [P(PgMA-r-PEGMA) -b-PMMA]. The P(PgMA-r-PEGMA)-b-PMMA grafting rate was 60.4% on the surface of magnetic sulfhydryl functionalized carbon nanotubes (mCNTs-SH) by click-reaction grafting. Poly (vinylidene fluoride) (PVDF)/CNTs composite ultrafiltration membranes were prepared using vapor-induced phase separation (VIPS) combined with magnetic field arraying. When the mCNTs-g-P(PgMA-r-PEGMA)-b-PMMA were vertically aligned in the PVDF membrane through a magnetic field, the effective construction of the vertical nanochannels was realized, and an increased purified water flux from 25.6 LMH to 35.8 LMH, with the composite ultrafiltration membranes was obtained. In addition, the membranes also showed excellent hydrophilicity, mechanical properties, and polyethylene glycol 1200 (PEG1200) rejection. The water contact angle was reduced from 105° to 79°, the rejection of PEG1200 was increased from 44% to 91% of the 0.5 g/L PEG aqueous solutions, and excellent mechanical properties (tensile strengthes up to 9.3 MPa) were achieved. By designing the interface structure of the CNTs and studying the orientation of the CNTs in PVDF membranes, this work provides a new research idea for the field of water treatment ultrafiltration membranes.

Effect of Nanophotocatalyst WO3 Addition on PVDF Membrane Characteristics and Performance

The addition of photocatalyst materials in the membrane has great potential to increase membrane performance and characteristics. In this study, nano photocatalysts WO3 were added to the polyvinylidene fluoride (PVDF) membrane for process water treatment from rubber industry. The results of SEM and XRD showed the presence of nano photocatalyst WO3, indicating the successfully embedded nano photocatalyst in PVDF membranes. The addition of nano photocatalyst materials has increased hydrophilicity by increasing the membrane's water uptake ability and decreasing the membrane's contact angle. The PVDF-WO3-2%wt membrane showed the highest flux value at 64.29 L m−2 h−1 with 96.40%, 85.61%, and 93.88% of chemical oxygen demand (COD), total dissolved solid (TDS), and ammonia rejection, respectively. The photocatalytic degradation effect of PVDF-WO3 is proven by a significant difference in the filtration results under vis-light irradiation. Membrane resulted in a better performance in photo-filtration (visible light) than in the dark condition. The PVDF-WO3-2%wt membrane also showed an excellent reusability after being used for 8 hours of the photo-filtration process. This research is promising to increase the use of photocatalytic membranes in rubber wastewater treatment into clean water.

Surface Microstructure Drives Biofilm Formation and Biofouling of Graphene Oxide Membranes in Practical Water Treatment.

Significant progress has been made previously in the research and development of graphene oxide (GO) membranes for water purification, but their biofouling behavior remains poorly understood. In this study, we investigated the biofilm formation and biofouling of GO membranes with different surface microstructures in the context of filtering natural surface water and for an extended operation period (110 days). The results showed that the relatively hydrophilic and smooth Fe(OH)3/GO membrane shaped a thin and spatially heterogeneous biofilm with high stable flux. However, the ability to simultaneously mitigate biofilm formation and reduce biofouling was not observed in the weakly hydrophilic and wrinkled Fe/GO and H-Fe(OH)3/GO membranes. Microbial analyses revealed that the hydrophilicity and roughness distinguished the bacterial communities and metabolic functions. The organic matter-degrading and predatory bacteria were more adapted to hydrophilic and smooth GO surfaces. These functional taxa were involved in the degradation of extracellular polymeric substances (EPS), and improved biofilm heterogeneity. In contrast, the weakly hydrophilic and wrinkled GO surfaces had reduced biodiversity, while unexpectedly boosting the proliferation of EPS-secreting bacteria, resulting in increased biofilm formation and aggravated biofouling. Moreover, all GO membranes achieved sustainable water purification during the entire operating period.

Chemistry of zeolites and zeolite based composite membranes as a cutting-edge candidate for removal of organic dyes & heavy metal ions: Progress and future directions

The quality of water has become a serious concern due to excessive industrial effluent production and poor wastewater treatment. Membrane technology has received immense attention due to its mild operating conditions, and highly efficient process. Polymer-based membranes are generally applied in various separation operations for their highly reproducible fabrication and low-cost approaches. Fouling aspects and the trade-off between selectivity and permeability are the main disadvantages of polymeric membranes. In this regard, zeolites are an attractive and promising candidate with 3D crystalline microporous systems, large and medium-pore molecular sieves, low-cost, and due to their distinct framework, are considered potential ceramic membranes for water treatment. Incorporating inorganic zeolite particles into the polymer matrix improves permeability while maintaining selectivity, and promotes mechanical strength in challenging environments and fouling conditions. Zeolite-based composite membranes can remove heavy metals and dye effluents from the aqueous medium thanks to their high adsorption capability and well-defined pore size. In this review, we focused on the significance of membranes in water treatment, structural/chemical features of zeolite-based membranes, and their design. The various strategies involved in integrating zeolites to obtain composite based membranes, an overview of toxicity issues of dyes, and heavy metals followed by an exploration of zeolite based composite membranes for the treatment of various dyes and heavy metal pollutants. Also, we tried to provide a cost analysis of zeolite-based membranes followed by commercial and industrial outlooks. Lastly, conclusion and future perspectives are drawn for the zeolite-based composite membranes.

Development and life cycle assessment (LCA) of super-oleophobic (under water) and super-hydrophilic (in-air) mesh membrane for oily water treatment

This paper reports the fabrication, characterization, and environmental impact analysis of a super-oleophobic (under water) and super-hydrophilic mesh membrane for oily water treatment. In order to prepare mesh membrane, Titania nanoparticles (NPs) were spray coated on mesh stainless steel followed by calcination at 500 °C. After that, the Titania-coated mesh membrane was characterized using contact angle goniometry (CA), XRD, FE-SEM, EDX and elemental mapping. The FE-SEM, EDX, elemental mapping and XRD results confirmed that the Titania NPs were successfully coated on the surface of mesh membrane. CA results demonstrated that the prepared mesh membrane is super-hydrophilic and super-oleo phobic under water conditions, making it suitable for oil/water separation. Subsequently, life cycle assessment (LCA) was performed to determine the environmental impacts of Titania NPs-coated mesh membrane fabrication process. LCA results indicate that electricity and nitrogen contributed the most toward the eighteen environmental impact categories considered for this study.

Highly permeable carbon nanotube membranes for efficient surface water treatment through separation and adsorption–electrochemical regeneration

Membrane-based processes feature many advantages for surface water treatment over other technologies; however, the trade-off between membrane selectivity and permeability usually results in the failure to obtain high-quality filtrate at a high permeance. In this study, we report a highly permeable sodium alginate/glutaraldehyde cross-linked carbon nanotube (CNT/SA-GA) membrane with high adsorption ability for surface water treatment. The CNT/SA-GA membranes have a well-formed hollow fiber morphology and good conductivity of 166–261 S/m. They could reject >98 % of large-sized molecules (e.g., Alcian Blue 8GX and Congo Red) at high permeances of 137–227 L/(m2·h·bar). Moreover, they could remove ~100 % of smaller molecules (e.g., Rhodamine B (RhB)) through dynamic adsorption with a capacity of ~57.3 mg/g. Benefiting from their good conductivity, the CNT/SA-GA membranes could easily decompose the pollutants after adsorption saturation through electrochemical oxidation and then regenerated themselves. Though the switch between adsorption and electrochemical oxidation (2.0 V), the CNT/SA-GA membranes could remove ~100 % RhB at a high permeance of 342 L/(m2·h·bar), which is one order of magnitude higher than those of nanofiltration membranes. When used for surface water treatment, the CNT/SA-GA membranes exhibited a much higher TOC removal rate than commercial poly(acrylonitrile) (PAN) membranes (56.2 % vs. 7.2 %). LC-MS/MS analysis showed that many small molecules such as caffeine could be effectively removed by the CNT/SA-GA membranes. In addition, they exhibited a higher fouling resistance than PAN membranes, evidenced by their lower permeance decline ratio (10.1 % vs. 43.7 %). This study will promote the development and applications of the CNT-based membranes for water purification.

A review on hydrophobic electrospun nanofibers-based materials and membranes for water treatment: Challenges, outlook, and stability

Membrane technology is well recognized as a dependable means of supplementing the availability of potable water through processes such as water purification and desalination. Electrospun nanofiber membranes have garnered significant attention because of their advantageous features, including a greater specific surface area, increased porosity, reduced thickness, and popularity. Consequently, ENMs have emerged as an up-and-coming contender in several applications. The various methods employed for fabrication involve inorganic deposition, polymer coating, and interfacial polymerization. Electrospun nanofiber membranes’ efficacy in removing diverse water pollutants, including heavy metals, dyes, and antibiotics, has been exceptional. The enhancement of polymer membrane performance can be achieved through the precise adjustment of polymer structure, manipulation of surface properties, and reinforcement of total membrane porosity. The study investigates the fundamentals of electrospun nanofibers and their utilization in electrospun nanofibrous membranes and composites for environmental remediation applications. The final section discusses the opportunities and significant challenges concerning the application of engineered nanomaterials in the water treatment sector. The advancement of engineered nanomaterials is anticipated to facilitate the growth and application of multiple industries, including water treatment and sustainability.

Fabrication of PVDF membranes via γ-ray irradiation and investigation into their membrane formation mechanisms and water treatment properties

Polyvinylidene fluoride (PVDF) membrane is a cheap and commonly used separation material, but its inherent hydrophobicity results in significant membrane contamination, which limits its engineering application and further development. The hydrophilic PVDF-g/co-NVP membrane was prepared through low-dose γ-ray irradiation and using N-vinyl-2-pyrrolidinone (NVP) as a modifier in this study. The effects of γ-ray dose and incorporating NVP additive on the microstructure, hydrophilicity, anti-fouling capability, and mechanical capacity of membranes were discussed. Molecular dynamics (MD) simulation method was used to comprehensively investigate the impact of the NVP on the physicochemical characteristics of membrane structure. Under a specific NVP load, the water contact angle of the membrane decreases from 87.92° to 52.66°. The pure water permeance reaches 362.1 L/m2 h, and the porosity increases to 55.21 %±1.29 %, which indicates that γ-ray irradiation with NVP addition can effectively adjust the pore structure and hydrophilicity of the membrane. During anti-fouling test against bovine serum albumin (BSA), the modified membrane exhibits remarkable anti-fouling characteristics, including reduced BSA accumulation, enhanced flux recovery, lower irreversible contamination level, and extended cleaning cycle compared with the original pure PVDF membrane because of its higher hydrophilicity and positive zeta-potential value. This study elucidates the mechanism underlying γ-ray graft modification of PVDF membranes, thereby providing valuable insights into the development of efficient functional membrane materials.

Process optimization for the removal of sodium diclofenac from water using a green polymeric membrane

New polymeric membranes for water treatment have been regularly developed and reported by the scientific community; however, process optimization based on the application purpose is necessary to achieve the best performance. In this work, a previously developed “green” polymeric membrane was employed to investigate the influence of process parameters on the removal of sodium diclofenac (DCF) from water. The “green” classification relies on the membrane components (poly(vinyl alcohol) – PVA, citric acid, glycerol, and green synthesized silver nanoparticles) and the mild conditions for its preparation. The parameters studied were the compaction and operational pressure (1.0 – 5.0 bar), feed temperature (10 – 25 °C), DCF concentration (0.002 – 0.010 g L−1), and feed pH (4.0 – 10.0). The results showed a positive influence of pressure on DCF removal (from 54 % to 75 %, within a range of 1.0–5.0 bar) due to the PVA structure densification, as well as the temperature (from 61 % to 82 %, within a range of 10–25 °C) because of the increased water affinity. The DCF concentration influenced the absorption of DCF into the membrane, reaching the maximum of 73 % of DCF removal at 0.007 – 0.010 g L−1. The feed pH determined the mechanism of removal but had a minor influence on the final performance (from 73 % of DCF removal at acidic pH to 77 % at alkaline conditions). The optimized conditions of 5 bar, 25 °C, 0.008 g L−1 DCF, and pH ∼5.75 promoted a permeability of 0.024 L m−2 h−1 bar−1 with 80 % DCF removal. This performance is comparable to that observed for commercial nanofiltration membranes but offers the advantage of a membrane fabricated and operated using a sustainable approach.

Sustainable membrane technology for water purification—Manufacturing, recycling and environmental impacts

Water pollution has become a serious threat to our ecosystem. Water contamination due to human, commercial, and industrial activities has negatively affected the whole world. Owing to the global demanding challenges of water pollution treatments and achieving sustainability, membrane technology has gained increasing research attention. Although numerous membrane materials have focused, the sustainable water purification membranes are most effective for environmental needs. In this regard sustainable, green, and recyclable polymeric and nanocomposite membranes have been developed. Materials fulfilling sustainable environmental demands usually include wide-ranging polyesters, polyamides, polysulfones, and recyclable/biodegradable petroleum polymers plus non-toxic solvents. Consequently, water purification membranes for nanofiltration, microfiltration, reverse osmosis, ultrafiltration, and related filtration processes have been designed. Sustainable polymer membranes for water purification have been manufactured using facile techniques. The resulting membranes have been tested for desalination, dye removal, ion separation, and antibacterial processes for wastewater. Environmental sustainability studies have also pointed towards desired life cycle assessment results for these water purification membranes. Recycling of water treatment membranes have been performed by three major processes mechanical recycling, chemical recycling, or thermal recycling. Moreover, use of sustainable membranes has caused positive environmental impacts for safe waste water treatment. Importantly, worth of sustainable water purification membranes has been analyzed for the environmentally friendly water purification applications. There is vast scope of developing and investigating water purification membranes using countless sustainable polymers, materials, and nanomaterials. Hence, value of sustainable membranes has been analyzed to meet the global demands and challenges to attain future clean water and ecosystem.