Rejection of trace organic water contaminants by an Aquaporin-based biomimetic hollow fiber membrane

Recent advances in surface tailoring of thin film forward osmosis membranes: A review

The recent advancements in fabricating forward osmosis (FO) membranes have shown promising results in desalination and water treatment. Different methods have been applied to improve FO performance, such as using mixed or new draw solutions, enhancing the recovery of draw solutions, membrane modification, and developing FO-hybrid systems. However, reliable methods to address the current issues, including reverse salt flux, fouling, and antibacterial activities, are still in progress. In recent decades, surface modification has been applied to different membrane processes, including FO membranes. Introducing nanochannels, bioparticles, new monomers, and hydrophilic-based materials to the surface layer of FO membranes has significantly impacted their performance and efficiency and resulted in better control over fouling and concentration polarization (CP) in these membranes. This review critically investigates the recent developments in FO membrane processes and fabrication techniques for FO surface-layer modification. In addition, this study focuses on the latest materials and structures used for the surface modification of FO membranes. Finally, the current challenges, gaps, and suggestions for future studies in this field have been discussed in detail.

Forward Osmosis Application for the Removal of Emerging Contaminants from Municipal Wastewater: A Review

Forward osmosis (FO) has attracted special attention in water and wastewater treatment due to its role in addressing the challenges of water scarcity and contamination. The presence of emerging contaminants in water sources raises concerns regarding their environmental and public health impacts. Conventional wastewater treatment methods cannot effectively remove these contaminants; thus, innovative approaches are required. FO membranes offer a promising solution for wastewater treatment and removal of the contaminants in wastewater. Several factors influence the performance of FO processes, including concentration polarization, membrane fouling, draw solute selection, and reverse salt flux. Therefore, understanding and optimizing these factors are crucial aspects for improving the efficiency and sustainability of the FO process. This review stresses the need for research to explore the potential and challenges of FO membranes to meet municipal wastewater treatment requirements, to optimize the process, to reduce energy consumption, and to promote scalability for potential industrial applications. In conclusion, FO shows promising performance for wastewater treatment, dealing with emerging pollutants and contributing to sustainable practices. By improving the FO process and addressing its challenges, we could contribute to improve the availability of water resources amid the global water scarcity concerns, as well as contribute to the circular economy.

Membrane technology for pesticide removal from aquatic environment: Status quo and way forward

The noxious side effects of pesticides on human health and environment have prompted the search of effective and reliable treatment techniques for pesticide removal. The removal of pesticides can be accomplished through physical, chemical and biologicals. Physical approaches such as filtration and adsorption are prevailing pesticide removal strategies on account of their effectiveness and ease of operation. Membrane-based filtration technology has been recognized as a promising water and wastewater treatment approach that can be used for a wide range of organic micropollutants including pesticides. Nanofiltration (NF), reverse osmosis (RO) and forward osmosis (FO) have been increasingly explored for pesticide removal from aquatic environment owing to their versatility and high treatment efficiencies. This review looks into the remedial strategies of pesticides from aqueous environment using membrane-based processes. The potentials and applications of three prevailing membrane processes, namely NF, RO and FO for the treatment of pesticide-containing wastewater are discussed in terms of the development of advanced membranes, separation mechanisms and system design. The challenges in regards to the practical implementation of membrane-based processes for pesticide remediation are identified. The corresponding research directions and way forward are highlighted. An in depth understanding of the pesticide nature, water chemistry and the pesticide-membrane interactions is the key to achieving high pesticide removal efficiency. The integration of membrane technology and conventional removal technologies represents a new dimension and the future direction for the treatment of wastewater containing recalcitrant pesticides.

Micropollutant removal capacity and stability of aquaporin incorporated biomimetic thin-film composite membranes

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Aquaporins increase the micropollutant removal capacity of TFC nanofiltration membranes.

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Biomimetic membrane prepared with Halomonas elongata aquaporin is applicable for micropollutant rejection.

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Aquaporin incorporated membrane is stable for six months period.

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Type of aquaporin and pore size of the membrane affect micropollutant rejection rates.

Aquaporin incorporated nanofiltration membranes have high potential for future applications on separation processes. In this study, performance of biomimetic thin-film composite membranes containing Halomonas elongata and Escherichia coli aquaporins with different affinity tags for the removal of micropollutants was investigated.% rejection of the membranes for atrazine, terbutryn, triclosan, and diuron varied between 66.7% and 90.3% depending on the type of aquaporin and micropollutant. The highest removal rate was achieved with a membrane containing H. elongata aquaporin for atrazine and terbutryn which have methyl branching in their structure. Electrostatic interactions between micropollutants, thin-film layer of the membrane, and tags of aquaporins may also play important role in rejection of micropollutants. Stability experiments showed that biomimetic membranes can be used for six months period without a remarkable decrease in% rejection. Membrane used 24 times for atrazine removal for a year period lost most of its ability to repel atrazine.

State-of-the-Art Organic- and Inorganic-Based Hollow Fiber Membranes in Liquid and Gas Applications: Looking Back and Beyond

The aggravation of environmental problems such as water scarcity and air pollution has called upon the need for a sustainable solution globally. Membrane technology, owing to its simplicity, sustainability, and cost-effectiveness, has emerged as one of the favorable technologies for water and air purification. Among all of the membrane configurations, hollow fiber membranes hold promise due to their outstanding packing density and ease of module assembly. Herein, this review systematically outlines the fundamentals of hollow fiber membranes, which comprise the structural analyses and phase inversion mechanism. Furthermore, illustrations of the latest advances in the fabrication of organic, inorganic, and composite hollow fiber membranes are presented. Key findings on the utilization of hollow fiber membranes in microfiltration (MF), nanofiltration (NF), reverse osmosis (RO), forward osmosis (FO), pervaporation, gas and vapor separation, membrane distillation, and membrane contactor are also reported. Moreover, the applications in nuclear waste treatment and biomedical fields such as hemodialysis and drug delivery are emphasized. Subsequently, the emerging R&D areas, precisely on green fabrication and modification techniques as well as sustainable materials for hollow fiber membranes, are highlighted. Last but not least, this review offers invigorating perspectives on the future directions for the design of next-generation hollow fiber membranes for various applications. As such, the comprehensive and critical insights gained in this review are anticipated to provide a new research doorway to stimulate the future development and optimization of hollow fiber membranes.

Optimization of Aquaporin Loading for Performance Enhancement of Aquaporin-Based Biomimetic Thin-Film Composite Membranes

The aquaporin-based biomimetic thin-film composite membrane (ABM-TFC) has demonstrated superior separation performance and achieved successful commercialization. The larger-scale production of the ABM membrane requires an appropriate balance between the performance and manufacturing cost. This study has systematically investigated the effects of proteoliposome concentration, protein-to-lipid ratio, as well as the additive on the separation performance of ABM for the purpose of finding the optimal preparation conditions for the ABM from the perspective of industrial production. Although increasing the proteoliposome concentration or protein-to-lipid ratio within a certain range could significantly enhance the water permeability of ABMs by increasing the loading of aquaporins in the selective layer, the enhancement effect was marginal or even compromised beyond an optimal point. Alternatively, adding cholesterol in the proteoliposome could further enhance the water flux of the ABM membrane, with minor effects on the salt rejection. The optimized ABM not only achieved a nearly doubled water flux with unchanged salt rejection compared to the control, but also demonstrated satisfactory filtration stability within a wide range of operation temperatures. This study provides a practical strategy for the optimization of ABM-TFC membranes to fit within the scheme of industrial-scale production.

Laboratory and pilot evaluation of aquaporin-based forward osmosis membranes for rejection of micropollutants

Aquaporin-based forward osmosis (AQP FO) membranes were applied both in laboratory- and pilot-scale for removing micropollutants from water. The effect of operating parameters (feed flow, draw flow, and transmembrane pressure) on the i) rejection of micropollutants, ii) water flux, iii) reverse salt flux, and iv) water recovery of the AQP FO membrane modules was studied. Among the 21 micropollutants spiked, only four compounds, atenolol, propranolol, metoprolol, and citalopram, permeated through the AQP FO membranes to an extent that they could be quantified in the draw solutions of both the laboratory and pilot systems. The rejection rates, based on the full mass balance calculations, were between 96.1% and 99.7%, and all the other 17 compounds showed rejection exceeding 90% on both systems. The pilot AQP FO system was further employed for six days to treat effluent from a membrane bioreactor (MBR) treating municipal wastewater. 35 micropollutants were investigated. 27 of these were identified and quantified in the MBR effluent. Minute fractions of gabapentin, benzotriazole, and metoprolol were detected passing through the AQP FO membranes into the draw side with a constant rejection of around 99.2%, 95.4%, and 99.9%. Almost all other micropollutants' minimum rejection rates exceeded 80%.

Effects of co-existence of organic matter and microplastics on the rejection of PFCs by forward osmosis membrane

Perfluorinated chemical (PFC)-based materials have been widely applied in industry. In this study, the influence of PFCs on the physicochemical properties of membranes and that of the co-existence of organic matter and microplastics on the removal rate in the process of forward osmosis (FO) was examined. The water flux, reverse salt flux, and rejection of PFCs were evaluated under w and w/o contaminants. The lowest rejection rates of PFCs in FO membranes were observed to be 92.2% and 90.4% for FO-TFC and PA-Aqua FO membranes, respectively. The main rejection mechanism of the FO membrane is the sieving effect (p-value: PA-TFC-0.015, PA-Aqua-0.002) based on molecular volume, which is more dominant than the electrostatic repulsive force and hydrophobic interaction, the major rejection mechanisms of existing trace contaminants. In addition, we observed that the effects of co-existing pollutants in raw water have an insignificant effect on the rejection of PFCs because of the physical and chemical stability of PFCs. According to the results of this study, using the FO membrane, PFCs can effectively control not only their self-existence but also when contaminants co-exist with them in water bodies.

Modeling the transport of neutral disinfection byproducts in forward osmosis: Roles of reverse salt flux

The rejection of disinfection byproducts (DBPs) is an important consideration for the application of forward osmosis (FO) in wastewater recycling. However, the transport of organic compounds in FO is not well predicted by existing models, partially because these models have not incorporated the effect of reverse salt flux, a phenomenon previously shown to influence the transport of pharmaceutical compounds. In this study, we investigated the effects of reverse salt flux on DBP transport in FO and the corresponding mechanisms. We used a commercial Aquaporin membrane and tested sixteen DBPs relevant to wastewater recycling. Using draw solutions constituted by NaCl, MgSO₄, or glucose in a bench-scale FO system, we first confirmed that higher reverse salt flux resulted in lower DBP permeance. By integrating results from the bench-scale FO system and those from diffusion cell tests, we showed that two mechanisms contributed to the hindered DBP transport: the steric hindrance in the active layer caused by the presence of the draw solute and the retarded diffusion of DBPs in the support layer via a "salting-out" effect. Lastly, we developed a modified solution-diffusion model incorporating these two mechanisms by accounting for the free volume occupied by draw solute molecules in the active layer and by introducing the Setschenow constant, respectively. The modified model significantly improved the prediction of permeance for halogenated DBPs, and revealed the relative importance of steric hindrance (dominant for large DBPs) and retarded diffusion (dominant for hydrophobic DBPs). The modified model did not accurately predict the permeance of nitrosamines, attributable to their extremely high hydrophilicity or large size.

Recent Progresses of Forward Osmosis Membranes Formulation and Design for Wastewater Treatment

Production of potable water or reclaimed water with higher quality are in demand to address water scarcity issues as well as to meet the expectation of stringent water quality standards. Forward osmosis (FO) provides a highly promising platform for energy-efficient membrane-based separation technology. This emerging technology has been recognized as a potential and cost-competitive alternative for many conventional wastewater treatment technologies. Motivated by its advantages over existing wastewater treatment technologies, the interest of applying FO technology for wastewater treatment has increased significantly in recent years. This article focuses on the recent developments and innovations in FO for wastewater treatment. An overview of the potential of FO in various wastewater treatment application will be first presented. The contemporary strategies used in membrane designs and fabrications as well as the efforts made to address membrane fouling are comprehensively reviewed. Finally, the challenges and future outlook of FO for wastewater treatment are highlighted.

Synthesis of Poly-Sodium-Acrylate (PSA)-Coated Magnetic Nanoparticles for Use in Forward Osmosis Draw Solutions

The synthesis of magnetic nanoparticles (MNPs) coated with hydrophilic poly-sodium-acrylate (PSA) ligands was studied to assess PSA-MNP complexes as draw solution (DS) solutes in forward osmosis (FO). For MNP-based DS, the surface modification and the size of the MNPs are two crucial factors to achieve a high osmolality. Superparamagnetic nanoparticles (NP) with functional groups attached may represent the ideal DS where chemical modifications of the NPs can be used in optimizing the DS osmolality and the magnetic properties allows for efficient recovery (DS re-concentration) using an external magnetic field. In this study MNPs with diameters of 4 nm have been prepared by controlled chemical co-precipitation of magnetite phase from aqueous solutions containing suitable salts of Fe²⁺ and Fe³⁺ under inert atmosphere and a pure magnetite phase could be verified by X-ray diffraction. Magnetic colloid suspensions containing PSA-coated MNPs with three different molar ratios of PSA:MNP = 1:1, 1:2 and 1:3 were prepared and assessed in terms of osmotic pressure, aggregation propensity and magnetization. Fourier Transform Infrared Spectroscopy (FTIR) confirmed the presence of PSA on coated MNPs and pristine PSA-MNPs with a molar ratio PSA:MNP = 1:1 exhibited an osmotic pressure of 30 bar. Molar ratios of PSA:MNP = 1:2 and 1:3 lead to the formation of less stabile magnetic colloid solutions, which led to the formation of aggregates with larger average hydrodynamic sizes and modest osmotic pressures (5.5 bar and 0.2 bar, respectively). After purification with ultrafiltration, the 1:1 nanoparticles exhibited an osmotic pressure of 9 bar with no aggregation and a sufficient magnetization of 25 emu/g to allow for DS regeneration using an external magnetic field. However, it was observed that the amount of PSA molecules attached to the MNPs decreased during DS recycling steps, leaving only strong chelate-bonded core-shell PSA as coating on the MNPs. This demonstrates the crucial role of MNP coating robustness in designing an efficient MNP-based DS for FO.

From channel proteins to industrial biomimetic membrane technology

Biomimetic membrane technology, based on the use of nano-scale functional additives in the form of channel proteins or artificially made channel structures, represents an attractive way of optimizing membrane separation technology. However, the nano-scale nature of the additives inherently points to the challenge in up-scaling the membranes to square meter areas. Thus, the ability to up-scale the processes involved in manufacturing will be crucial for translating the protein/nano-science into technology. Here we discuss how highly selective aquaporin proteins can be used to enhance the performance of the classical thin film composite membrane, and how this can be used in relevant membrane elements and module form factors. A particular up-scaling challenge lies in securing large scale membrane protein production. We demonstrate our framework for making batch amounts which are compatible with the large scale production of biomimetic membranes for water purification based on the use of the E. coli expression system.

Hollow fiber nanofiltration membranes with integrated aquaporin Z

AqpZ reconstituted proteoliposomes integrated into polyamide matrix using different ultrafiltration support membranes successfully with a performance increase of 12 times.