Regenerable biocatalytic nanofiltration membrane for aquatic micropollutants removal

Rejection of an emerging small neutral organic micropollutant by in-situ nanofiltration membrane modification for water treatment

Nanofiltration (NF) membranes are recognized for their potential in removing organic micropollutants (OMPs). However, the limited efficiency of commercial NF membranes in removing small and neutral emerging OMPs has impeded its wide use. This study explores the effectiveness of in-situ modification of commercial NF270 membranes using two monomers for the removal of 1H-benzotriazole (BTA). For the first time, this work investigates the physicochemical properties of commercial NF270 membranes grafted with these two monomers, 3-(trimethoxysilyl)propyl methacrylate and 2-(diethylamino)ethyl methacrylate, using different surface characterization techniques. The study also evaluates the performance of both unmodified and modified membranes in the rejection of BTA and compares the results with state-of-the-art monomers. The 2-(diethylamino)ethyl methacrylate-grafted membranes show a modest enhancement of 12 % in BTA rejection. In contrast, the 3-(trimethoxysilyl)propyl methacrylate-modified membranes exhibit a remarkable 107 % improvement in BTA rejection compared to the virgin NF270 membrane, achieving the highest increase in OMP removal among current state-of-the-art monomer-modified membranes reported in previous research. This approach effectively removes BTA primarily through the mechanisms of size exclusion and hydrophobic interactions. This research presents a comprehensive strategy for surface modification of NF membranes, offering potential improvements in the rejection of small and neutral OMPs for water treatment.

Ultrafiltration and composite microfiltration biocatalytic membrane activity and steroid hormone micropollutant degradation at environmentally relevant concentrations

Biocatalytic degradation of micropollutants has been extensively explored in both batch and membrane reactors in µg/L to mg/L concentrations and variable water compositions. The degradation of micropollutants by biocatalytic membranes at environmentally relevant concentrations of ng/L range found in natural surface water matrices has not yet been investigated, presumably because of the challenging concentration analysis. This study investigated the limitations of biocatalytic degradation of estradiol (E2) micropollutant at environmentally relevant concentrations by a biocatalytic membrane. The contributions of solute flux, hydraulic residence time (HRT) and water matrix composition on reaction kinetics, the apparent rate of disappearance (or reaction rate) and enzyme activity were examined. Two biocatalytic membranes were used: i) laccase entrapped in an ultrafiltration (UF) membrane support (namely UF-SNPs) and, ii) laccase covalently bound to the nanofiber matrix of a composite microfiltration (MF) membrane. The three main findings are reported. Firstly, the apparent rate of E2 disappearance decreases significantly by four orders of magnitude at a low micropollutant concentration of 0.1 µg/L, resulting in undetectable degradation during filtration, irrespective of the biocatalytic membrane. Secondly, the solute mass transfer and HRT control the biocatalytic degradation through the membranes resulting in different E2 removal. For the UF-SNPs membrane, a removal of 31 % is achieved only by increasing the concentration to 3000 µg/L and at a flux of 60 L/m².h (HRT of 4.5 s) due to an increase in solute flux by an order of magnitude similar to the apparent rate of disappearance. In contrast, the nano-MF membrane is ineffective in achieving biocatalytic degradation regardless of E2 concentration, as the HRT is approximately seven times lower (0.6 s) than that of the UF-SNPs, and thus insufficient for E2 to reach the catalytic site. Thirdly, the composition of the aqueous matrix plays a crucial role in the control of laccase activity irrespective of the membrane. Indeed, laccase is inactivated predominantly by chloride ions in synthetic carbonate buffer, since the typical NaCl concentration is about two orders of magnitude higher than E2 concentration. This study highlights that the slower kinetics achieved in the biocatalytic UF-SNPs and MF membranes are ineffective in removing steroid hormone micropollutants at realistic concentrations in surface water matrices. Further research is suggested to accelerate the reaction kinetics at such low concentrations and prolong the residence time within the membrane.

Immobilized enzymatic membrane surfaces for biocatalytic organics removal and fouling resistance

This research reported on the immobilization of environmentally friendly enzymes, such as horseradish peroxidase (HRP) and laccase (L), along with the hydrophilic zwitterionic compound l-DOPA on nano-filtration (NF) membranes. This approach introduced biocatalytic membranes, leveraging combined effects between membranes and enzymes. The aim was to systematically assess the efficacy of the enzymatic modified membrane (HRP-NF) in degrading colors in the wastewater, as well as enhancing the membrane resistance toward organic fouling. The enzymatic immobilized membrane demonstrated 96.3 ± 1.8% to 96.6 ± 1.9% removal of colors, and 65.2 ± 1.3% to 67.2 ± 1.3% removal of TOC. This result was underpinned by the insights obtained from the radical scavenger coumarin, which was employed to trap and confirm the formation of PRs through the reaction of enzymes and H2O2. Furthermore, membranes modified with enzymes exhibited significantly improved antifouling properties. The HRP-NF membrane experienced an 8% decline in flux, while the co-immobilized HRP-L-NF membrane demonstrated as low as 6% flux decline, contributed by the synergistic effect of increased hydrophilicity and biocatalytic effects. These findings confirmed that the immobilized enzymatic surface has added function of degrading contaminants in addition to separation function of nanofiltration membrane. These l-DOPA-immobilized enzymatic membranes offered a promising hybrid biocatalytic membrane to eliminate dyes and mitigate membrane fouling, which can be applied in many industrial and domestic water and wastewater treatment.

Amine-Rich Hydrogels for Molecular Nanoarchitectonics of Photosystem II and Inverse Opal TiO2 toward Solar Water Oxidation

Solar water oxidation is a crucial process in light-driven reductive synthesis, providing electrons and protons for various chemical reductions. Despite advances in light-harvesting materials and cocatalysts, achieving high efficiency and stability remains challenging. In this study, we present a simple yet effective strategy for immobilizing natural photosystems (PS) made of abundant and inexpensive elements, using amine-rich polyethylenimine (PEI) hydrogels, to fabricate organic/inorganic hybrid photoanodes. Natural PS II extracted from spinach was successfully immobilized on inverse opal TiO2 photoanodes in the presence of PEI hydrogels, leading to greatly enhanced solar water oxidation activity. Photoelectrochemical (PEC) analyses reveal that PS II can be immobilized in specific orientations through electrostatic interactions between the positively charged amine groups of PEI and the negatively charged stromal side of PS II. This specific orientation ensures efficient photogenerated charge separation and suppresses undesired side reactions such as the production of reactive oxygen species. Our study provides an effective immobilization platform and sheds light on the potential utilization of PS II in PEC water oxidation.

Bioinspired laccase-mimicking catalyst for on-site monitoring of thiram in paper-based colorimetric platform

A long-standing goal has been to create artificial enzymes with natural enzyme-like catalytic activity. Herein, a laccase-mimicking catalyst (GSH-Cu) is designed by simulating the copper active sites and spatial amino acid microenvironment of natural enzymes. In particular, the engineered GSH-Cu shows a catalytic function that conforms to Michaelis-Menten kinetics of natural laccase. The high catalytic activity of GSH-Cu can be easily inhibited by thiram through surface passivation to produce copper nanoparticles. We demonstrate that the developed GSH-Cu with high stability and recyclability can be used to fabricate effective colorimetric sensor for sensitive detection of thiram. The resulting absorption intensity can be employed to quantify thiram in the range of 2.5-250 ng mL^-1, which meets the detection requirement in fruit. Bestowed with the feasibility analysis of colorimetric output, a portable platform is designed by integrating GSH-Cu based test paper with a conventional smartphone for conveniently on-site quantified thiram. The proposed strategy about engineering enzyme-mimicking catalysts with excellent catalytic performance will open avenues for boosting the sensing application.

Biocatalytic membranes for combating the challenges of membrane fouling and micropollutants in water purification: A review

Over the last few years, the list of water contaminants has grown tremendously due to many anthropogenic activities. Various conventional technologies are available for water and wastewater treatment. However, micropollutants of emerging concern (MEC) are posing a great threat due to their activity at trace concentration and poor removal efficiency by the conventional treatment processes. Advanced technology like membrane technology can remove MEC to some extent. However, issues like the different chemical properties of MEC, selectivity, and fouling of membranes can affect the removal efficiency. Moreover, the concentrate from the membrane filtration may need further treatment. Enzymatic degradation of pollutants and foulants is one of the green approaches for removing various contaminants from the water as well as mitigating membrane fouling. Biocatalytic membranes (BCMs), in which enzymes are immobilized on membranes, combines the advantages of membrane separation and enzymatic degradation. This review article discussed various commonly used enzymes in BCMs for removing MEC and fouling. The majorly used enzymes were oxidoreductases and hydrolases for removing MEC, antifouling, and self-cleaning ability. The various BCM synthesis processes based on entrapment, crosslinking, and binding have been summarized, along with the effects of the addition of the nanoparticles on the performances of the BCMs. The scale-up, commercial viability, challenges, and future direction for improving BCMs have been discussed and shown bright possibilities for these new generation membranes.

Nanofiltration for separation and purification of saccharides from biomass

Saccharide production is critical to the development of biotechnology in the field of food and biofuel. The extraction of saccharide from biomass-based hydrolysate mixtures has become a trend due to low cost and abundant biomass reserves. Compared to conventional methods of fractionation and recovery of saccharides, nanofiltration (NF) has received considerable attention in recent decades because of its high selectivity and low energy consumption and environmental impact. In this review the advantages and challenges of NF based technology in the separation of saccharides are critically evaluated. Hybrid membrane processes, i.e., combining NF with ultrafiltration, can complement each other to provide an efficient approach for removal of unwanted solutes to obtain higher purity saccharides. However, use of NF membrane separation technology is limited due to irreversible membrane fouling that results in high capital and operating costs. Future development of NF membrane technology should therefore focus on improving material stability, antifouling ability and saccharide targeting selectivity, as well as on engineering aspects such as process optimisation and membrane module design.

Ultra-low pressure cellulose-based nanofiltration membrane fabricated on layer-by-layer assembly for efficient sodium chloride removal

Cellulose is a renewable, biodegradable, biocompatible, and sustainable material. A bamboo cellulose-based nanofiltration membrane (LBL-NF-CS/BCM) was prepared with a combination of layer-by-layer assembly and spraying methods. The chemical structure, morphology, and surface charge of the resultant LBL-NF-CS/BCM composite membranes were characterized based on Thermo Gravimetric Analysis (TGA), X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), and X-ray Photoelectron Spectroscopy Scanning (XPS). The nanofiltration performance of the LBL-NF-CS/BCM composite membranes was evaluated using 500 ppm NaCl solutions under 0.3 MPa pressure. It was found that the LBL-NF-CS/BCM composite membranes had a rejection rate of about 36.11 % against a 500 ppm NaCl solution under the conditions tested, and membrane flux of about 12.08 L/(m² h) was reached. The combined layer-by-layer assembly and spraying provides a scalable and convenient process concept for nanofiltration membrane fabrication.

Biocatalytic membrane: Go far beyond enzyme immobilization

Biocatalytic membrane takes advantages of reaction-separation integration as well as enzyme immobilization, which has attracted increasing attentions in online detection and biomanufacturing. However, the high preparation cost, inferior comprehensive performance, and low stability limit its applications. Thus, besides enzyme immobilization, more efforts should be made in biocatalytic membrane configuration design for a specific application to enhance the synergistic effect of reaction and separation and improve its operating stability. This review summarized the recent progress on biocatalytic membrane preparation, discussed different membrane configurations for various applications, finally proposed several challenges and possible solutions, which provided directions and guides for the development and industrialization of biocatalytic membrane.

Sharpening Nanofiltration: Strategies for Enhanced Membrane Selectivity

Nanofiltration plays an increasingly large role in many industrial applications, such as water treatment (e.g., desalination, water softening, and fluoride removal) and resource recovery (e.g., alkaline earth metals). Energy consumption and benefits of nanofiltration processes are directly determined by the selectivity of the nanofiltration membranes, which is largely governed by pore-size distribution and Donnan effects. During operation, the separation performance of unmodified nanofiltration membranes will also be impacted (deleteriously) upon unavoidable membrane fouling. Many efforts, therefore, have been directed toward enhancing the selectivity of nanofiltration membranes, which can be classified into membrane fabrication method improvement and process intensification. This review summarizes recent developments in the field and provides guidance for potential future approaches to improve the selectivity of nanofiltration membranes.

Biomimetic dynamic membrane (BDM): Fabrication method and roles of carriers and laccase

Biomimetic dynamic membrane (BDM) has been employed as a promising membrane separation technology regarding water/wastewater treatment (Model pollutant is methylene blue). Given its catalytic function on micro-pollutant removal and fouling control, detailed mechanism for impacts of fabrication method, carriers (CNT and GO) and laccase on the construction of biomimetic layer and enzyme immobilization have not been clear so far. In this work, the BDM performance with various fabrication methods, carriers and laccase were investigated and verified. The BDM fabrication tests demonstrated that BDM with mixed filtration method had better filtration performance (up to 120 L m^-2 h^-1 flux and 80% removal rate) than BDM with stepwise filtration method. Moreover, the laccases immobilized on GO exhibited a stronger laccase activity than those on CNT. Increasing CNT or GO dosage strengthened removal rate, but lowered flux, meanwhile flux and removal rate exhibited a significant fluctuation with certain laccase dosage. At 25 g m^-2 CNT or GO dosage and 50 g m^-2 laccase dosage, the optimized flux and removal rate values were obtained. Further study investigated the surface morphology and property of BDM, showing that BDM with mixed filtration method turned out to be the optimized enzyme immobilization mechanism and fabrication method. In addition, during multiple filtration cycles, with the optimized conditions, the removal rate, flux and laccase activity of BDM could maintain at high levels. On account of the finding of the present study, selecting a suitable fabrication method, appropriate CNT or GO dosage and laccase dosage can indeed optimize the structure of biomimetic layer and enzyme immobilization, expanding its possibility on sustainable operation.

A novel cellulose/chitosan composite nanofiltration membrane prepared with piperazine and trimesoyl chloride by interfacial polymerization

Bamboo cellulose (BC) is one of the most abundant renewable, hydrophilic, inexpensive, and biodegradable organic materials. The cellulose membrane is one of the best materials for replacing petroleum-based polymer films used for water purification. In this study, N-methylmorpholine-N-oxide (NMMO) was used as a solvent to dissolve cellulose and chitosan, and a regenerated cellulose/chitosan membrane (BC/CSM) was prepared by phase inversion. A new kind of cellulose/chitosan nanofiltration membrane (IP-BC/CS-NFM) was obtained by the interfacial polymerization of piperazine (PIP) and trimesoyl chloride (TMC). The IP-BC/CS-NFM was characterized by Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), thermal gravimetric analysis (TGA), the retention rate, and water flux. FT-IR analysis showed that polypiperazine amide was formed. Additionally, FE-SEM and AFM showed that a uniform roughness and dense functional layer was formed on the surface of the IP-BC/CS-NFM. Furthermore, TGA analysis showed that the thermal stability of IP-BC/CS-NFM is better than that of BC/CSM. The inorganic salt retention of IP-BC/CS-NFM was measured using a membrane performance evaluation instrument, following the order R(Na2SO4) > R(MgSO4) > R(MgCl2) > R(NaCl). At a pressure of 0.5 MPa, the retention rates for NaCl, Na2SO4, MgSO4, MgCl2, Methyl Orange, and Methyl Blue were 40.26%, 71.34%, 62.55%, 53.28%, 93.65%, and 98.86%, and the water flux values were 15.64, 13.56, 14.03, 14.88, 13.28, and 12.35 L m-2 h-1, respectively. The IP-BC/CS-NFM showed better water flux and a higher rejection rate in aqueous dye-salt solutions, and had a good separation performance under different operating pressure conditions.

A comprehensive review of the structures and properties of ionic polymeric materials

This review focuses on the mechanistic approach, the structure–property relationship and applications of ionic polymeric materials.

Photo-Fenton-like degradation of bisphenol A by persulfate and solar irradiation

This work evaluates the feasibility of a solar-enhanced Fenton-like process using S₂O₈^2- (PS) and Fe²⁺ for the elimination of BPA, a model endocrine-disruption compound. This comparative study of BPA removal showed that among the approaches employed, the effectiveness of BPA degradation (10 mg/L) decreased in the order: Solar/PS/Fe²⁺> Solar/PS > PS/Fe²⁺> Solar/Fe²⁺> Solar. The complete degradation of BPA was achieved by Solar/PS/Fe²⁺ treatment at a [PS]:[BPA] ratio of 20 in less than t_30W 5 in deionised water. The high efficiency of the Solar/PS/Fe²⁺ process revealed a synergistic effect (ϕ = 2.38) between the applied activation agents on the formation of reactive oxygen species (ROS) and subsequent decomposition of BPA. The treatment was accompanied by total organic carbon (TOC) removal (44%) in 45 min. Sequential generation of reactive oxygen species has made Solar/PS/Fe²⁺ a kinetically effective process for removing BPA without accumulation of toxic intermediates. The reaction rate followed pseudo-first-order kinetics that increased with increasing PS and Fe²⁺ concentrations. Experimental evidence suggests that exposure to solar irradiation maintains suitable quantities of free Fe²⁺ in the reaction mixture, even at low catalyst concentrations (the molar ratio of [PS]:[Fe²⁺] varied from 1:0.01 to 1:0.08). The effects of HCO₃^-, SO₄^2-, and Cl^- were also examined. As expected, HCO₃^- and SO₄^2- inhibited BPA oxidation. The effect of Cl^- on the oxidation efficiency of BPA in Fenton-like systems depends not only on actual Cl^- concentrations but it is also highly influenced by molar ratios of Cl^- to oxidant and catalyst. Inhibition, which was caused by Cl^- in the mM range can be overcome by prolonging the reaction time or increasing the initial Fe²⁺concentration. Finally, the efficiency of Solar/PS/Fe²⁺ process was examined in diluted natural surface water and wastewater effluent. On eliminating the buffering action of HCO₃^-/CO₃^2- ions by lowering the pH value to 4.5, complete BPA degradation was achieved in all real water matrices.

Enzymatic Cascade Catalysis in a Nanofiltration Membrane: Engineering the Microenvironment by Synergism of Separation and Reaction

Microenvironment plays a significant role in enzymatic catalysis, which directly influences enzyme activity and stability. It is important to regulate the enzyme microenvironment, especially for the liquid with unfavored properties (e.g., pH and dissolved oxygen). In this work, we propose a methodology that can regulate pH and substrate concentration for enzymatic catalysis by a biocatalytic membrane, which is composed of glucose oxidase (GOx) and horseradish peroxidase (HRP) co-immobilized in a polyamide nanofiltration (NF) membrane (i.e., beneath the separation layer). By virtue of the selective separation function of NF membrane and in situ production of organic acid/electron donor with GOx, a synergism effect of separation and reaction in the liquid/solid interface was manipulated for engineering the microenvironment of HRP to enhance its activity and stability for micropollutant removal in water. The outcome of this work not only provides a new methodology to precisely control enzymatic reaction but also offers a smart membrane system to efficiently and steadily remove the micropollutants in portable water.

Gravity-driven catalytic nanofibrous membrane with microsphere and nanofiber coordinated structure for ultrafast continuous reduction of 4-nitrophenol

Silver loaded nanofibrous membrane with high catalytic performance for 4-nitrophenol under continuous gravity-driven filtration was developed in this study. A polydopamine (PDA) microsphere and nanofiber coordinated composite structure was fabricated through an in situ PDA synthesis to achieve a high catalyst loading and controllable residence time of 4-nitrophenol. The incorporated PDA microspheres played an important role for the enhancement of catalytic performance due to the increased surface area (23% increase compared with PAN and PAN-PDAs-Ag) and reduced membrane porosity. Silver loading amount and the residence time of 4-nitrophenol was increased by more than 108% (from 1.2 wt% to 2.5 wt%) and 45% (from 0.79 s to 1.15 s) when comparing with PAN-PDAc-Ag and PAN-PDAs-Ag nanofibrous membrane. The conversion rate of 4-nitrophenol in a gravity-driven filtration process was as high as 97% when PAN-PDAs-Ag nanofibrous membrane was used, which was much higher than the PAN-PDAc-Ag membrane (80%). In addition, the PAN-PDAs-Ag nanofibrous membrane exhibited excellent recycle performance, the conversion rate was maintained as high as 93% after five times of reuse. The microsphere and nanofiber coordinated structure with enhanced surface area and controllable residence time of contaminants proposed in this study might advance the real applications of electrospun nanofibrous membrane for catalytic removal of contaminants.

A Novel Nanocomposite Membrane Combining BN Nanosheets and GO for Effective Removal of Antibiotic in Water

Residual antibiotics in water have become a primary source of water pollution due to their misuse. Recently, membranes, produced by layered nanomaterials such as graphene oxide (GO), boron nitride (BN) and transition metal dichalcogenides, have been used in water purification, desalination and molecule separation as they are energy saving and simple to operate. The performance of membranes is closely related to their structure and the properties of the nanomaterials used. In this work, BN nanosheets (BNNSs) and GO were used to fabricate a two-dimensional nanocomposite membrane in order to improve the membrane’s permeance. It should be mentioned that the corresponding equal mass of the pure GO membrane was almost impermeable for the antibiotic solution. Multi-walled carbon nanotubes (MWCNTs) were inserted into the GO layers to increase the interlayer spacing and adsorb more antibiotics from the water. The resultant MWCNTs/BNNSs/GO membranes showed improved permeance and stable sieving capability for the antibiotic and small species. Specifically, permeance reached 30.2 L m⁻² h⁻¹ bar⁻¹, which was much higher than pure GO membrane and the antibiotic rejection was 96.1%.

Non-Polyamide Based Nanofiltration Membranes Using Green Metal-Organic Coordination Complexes: Implications for the Removal of Trace Organic Contaminants

Polyamide-based thin film composite (TFC) membranes are generally optimized for salt rejection but not for the removal of trace organic contaminants (TrOCs). The insufficient rejection of TrOCs such as endocrine disrupting compounds (EDCs) by polyamide membranes can jeopardize product water safety in wastewater reclamation. In this study, we report a novel nonpolyamide membrane chemistry using green tannic acid-iron (TA-Fe) complexes to remove TrOCs. The nanofiltration membrane formed at a TA-Fe molar ratio of 1:3 (TA-Fe3) had a continuous thin rejection layer of 10-30 nm in thickness, together with a water permeability of 5.1 Lm^2-h^-1bar^-1 and a Na₂SO₄ rejection of 89.7%. Meanwhile, this membrane presented significantly higher rejection of EDCs (up to 99.7%) than that of polyamide membranes (up to 81.8%). Quartz crystal microbalance results revealed that the sorption amount of a model EDC, benzylparbaen, by TA-Fe3 layer was nearly 2 orders of magnitude less than that by polyamide, leading to reduced transmission and higher rejection. Further analysis of membrane revealed a much greater water/EDC selectivity of the TA-Fe3 membrane compared to the polyamide membranes.

Solution Blown Nylon 6 Nanofibrous Membrane as Scaffold for Nanofiltration

In this work, a nylon 6 nanofibrous membrane was prepared via solution blowing technology and followed hot-press as scaffold for nanofiltration. The structure and properties of the hot-pressed nylon 6 nanofibrous membrane (HNM) were studied the effect of hot-pressing parameters and areal densities. Then an ultra-thin polyamide (PA) active layer was prepared by interfacial polymerization on HNM. The effects of nanofibrous scaffolds on the surface properties of ultra-thin nanofiltration membranes and their filtration performance were studied. Results showed that the nylon 6 nanofibers prepared at a concentration of 15 wt % had a good morphology and diameter distribution and the nanofibers were stacked more tightly and significantly reduced in diameter after hot pressing at 180 °C under the pressure of 15 MPa for 10 s. When the porous scaffold was prepared, HNM with an areal density of 9.4 and 14.1 g/m² has a better apparent structure, a smaller pore size, a higher porosity and a greater strength. At the same time, different areal densities of HNM have an important influence on the preparation and properties of nanofiltration membranes. With the increase of areal density, the uniformity of HNM increased while their surface roughness and pore size decreased, which is beneficial to the establishment of PA barrier layer. With areal density of 9.4 and 14.1 g/m², the as-prepared nanofiltration membrane has a smoother surface and more outstanding filtration performance. The pure water flux is 13.1 L m⁻² h⁻¹ and the filtration efficiencies for NaCl and Na₂SO₄ are 81.3% and 85.1%, respectively.

Separation and purification using GO and r-GO membranes

Many materials with varied characteristics have been used for water purification and separation applications. Recently discovered graphene oxide (GO), a two-dimensional derivative of graphene has been considered as a promising membrane material for water purification due to its excellent hydrophilicity, high water permeability, and excellent ionic/molecular separation properties. This review is focussed on the possible versatile applicability of GO membranes. It is also known that selective reduction of GO results in membranes with a pore size of ∼0.35 nm, ideally suited for desalination applications. This article presents the applicability of graphene-based membranes for multiple separation applications. This is indeed the first review article outlining a comparison of GO and r-GO membranes and discussing the suitability for applications based on the porosity of the membranes.

This review article outlines a comparison of GO and r-GO membranes for separation and purification applications.