Forward Osmosis Applications Research Articles

Forward osmosis for concentrating lithium-enriched brine: From membrane performance to system design

Using concentrated salt-lake brine as the draw solution (DS), forward osmosis (FO) has been proposed as the low carbon footprint concentration technology for extracting water from lithium-enriched brine. From membrane modules to a process, there exist tremendous risks when considering total cost in time and investment for a trial. To address this issue, a bridge between the FO membrane/ module characteristics and a FO system design is highly desirable. This study for the first time developed a system design model using hollow fiber (HF) FO membrane modules for FO concentration of lithium-enriched brine. The concentration polarization along the module, the membrane structural parameters (S), crossflow velocity, and DS concentration were the main factors considered in the model. The effect of all factors on module water flux and total membrane area was systematically investigated for a typical industrial output of 10 k ton of Li2CO3. A master curve of the water flux verse feed concentration for the tailor-made HF modules was utilized as the basis. On a module scale, the structural parameter S is of first importance and indicates requirement of FO membranes with low S. The crossflow velocity has relatively small impact to the membrane area, but not negligible. On a system scale, the empirical equation of the structural parameters and crossflow velocity on the theoretical minimum system membrane area was summarized. The results show that increasing the stages can reduce the number of modules and required DS flow. Increasing DS dilution rate in system design efficiently utilizes the osmotic pressure of DS. The present model serves as a practical solution for process optimization and FO membrane selection. The methodology is valuable for other FO applications using HF FO membranes.

Forward osmosis membrane process: A review of temperature effects on system performance and membrane parameters from experimental studies

Forward osmosis (FO) offers a promising solution for concentration and material recovery, characterized by its low energy consumption and high separation efficiency. Temperature exerts a significant influence on FO, affecting permeation performance, membrane characteristics, and solution chemistry. The review article shows that increasing temperatures enhance forward permeate flux and solvent recovery by modifying mass transfer coefficients, membrane structure, and solution properties like osmotic pressure, diffusivity, and viscosity. This helps alleviate concentration polarization, a key challenge in FO applications. However, higher temperatures can exacerbate reverse solute flux, diminish solute rejection, and amplify membrane fouling, impacting operational efficiency and effluent quality. Studies involving thermoresponsive compounds or high-solute-content solutions yield conflicting results, further complicated by thermo-osmosis in scenarios with temperature gradients between solutions. In water and wastewater treatment, a huge quantity of solutions is treated, and temperature control is difficult. Managing solution temperatures through the utilization of waste hot streams or available heat sources can offer a viable strategy for enhancing system efficiency and mitigating the detrimental impacts of temperature fluctuations, while the solution volume should be effectively reduced before the treatment. A nuanced comprehension of temperature’s impacts is imperative for refining FO systems and addressing challenges across various industrial and environmental sectors.

Recycling scale inhibitor wastes into pH-responsive complexes to treat wastewater produced from spent lithium-ion battery disposal

A large amount of organophosphorus-containing wastewater is produced in spent lithium-ion battery disposal. Forward osmosis (FO) offers unique advantages in purifying this kind of wastewater if suitable draw solutes – the core of FO technology, are available. Herein we synthesize several pH-sensitive zinc complexes, namely ZnATMP-iNa (i = 0, 1, 2, 3, 4), from ZnSO4 and amino tris(methylene phosphonic acid) (ATMP) obtained from scale inhibitor wastes for organophosphorus-containing wastewater remediation. Among these ZnATMP-iNa, ZnATMP-3Na best meets the standards of an ideal draw solute. This makes ZnATMP-3Na outperform other reported draw solutes. 0.6 M ZnATMP-3Na produces a water flux of 12.7 LMH, 136 % higher than that of NaCl and a solute loss of 0.015 g/L, lower than that of NH4HCO3 (0.83 g/L). In organophosphorus-containing wastewater treatment, ZnATMP-3Na has higher water recovery efficiency (8.3 LMH) and sustainability than NaCl and NH4HCO3, and is sufficient to handle large quantities of wastewater. Remarkably, the pH-responsive property allows ZnATMP-3Na to be readily recovered through pH-control and reused in FO. The ionic property, expanded cage-like structure and easy-recycling make ZnATMP-3Na achieve sustainable FO separation and superior to other draw solutes. This study provides inspiration for draw solute design from wastes and extends FO application to organophosphorus-containing wastewater remediation.

Thermo- and CO2-Responsive Copolymers for Forward Osmosis Applications

Thermo- and CO₂-Responsive Copolymers for Forward Osmosis Applications

Optimal synergy between FO membrane and draw solute for high-efficient fruit juice concentration and simultaneous fruiter fertigation

The technology of forward osmosis (FO) has garnered increasing research interest for its excellent advantages in producing high-quality concentrated juice. However, the practical application of FO to concentrate juice is hindered by the lack of an appropriate FO membrane and matched draw solution. To address this challenge, several additives containing high-valence ions were investigated to improve the feasibility of the FO process for juice concentration, using a nanofiltration(NF)-like FO membrane with an interlayer constructed by MOFs-based nanoparticles. The prepared NF-like FO membranes exhibited negative potential, superior hydrophilicity, and uneven crosslinking, which matched well with five selected additives (C6H8O7, K2SO4, C6H5K3O7, MgSO4, and KH2PO4), potentially preventing bacterial growth on the membrane surface during the concentration process and contributing to the growth of plants. A comprehensive comparison of selected five additives indicated that, with the exception of MgSO4, these additives at their saturated concentration exhibited marginally higher osmotic pressure than that of the fresh juice, indicating their limited suitability for further concentration of the fresh juice. However, during the pre-concentration phase of the fresh juice, the juice concentration is lower than that of the fresh juice due to the additional water incorporated during the juice production process. C6H5K3O7 was the optimal draw solution for pre-concentrating apple juice, while MgSO4 was better suited for further concentrating fresh juice. The concentrations of C6H5K3O7 and MgSO4 in the final juice were well below their limit value. Based on these results, a proposal for a dual-stage and dual-cycle FO process has demonstrated to achieve highly efficient concentration of fruit juice and seamless integration of juice production and fertigation of fruit trees, without the need to consider draw solution recovery.

Optimal cross-linking of MXene-based membranes for high rejection and low adsorption with long-term stability for water treatment

The unique layered structure and abundant 2D nanochannels of MXene membranes have demonstrated outstanding permeability, indicating their great potential in the field of water treatment. However, their unstable interlayer spacing and irregular layer structure have limited their ability to separate small molecular pollutants effectively. In this study, we successfully prepared composite MXene membranes with high rejection and low adsorption properties by exploiting the differences in the surface functional groups and chain lengths of dopamine (DA) and polyethylene glycol (PEG) through an optimal cross-linking approach. These composite membranes exhibited excellent stability in terms of interlayer spacing and mitigated the adverse effects of stacking defects. Compared to MXene membranes, the composite membranes achieved a 1.76-fold increase in dye rejection efficiency, reaching 98.7% at most, with an adsorption ratio of only 1.8%. Moreover, outstanding performances were also exhibited in pressure and concentration load tests. Furthermore, in the context of forward osmosis applications, the composite membranes demonstrated excellent Na+ rejection of 99.9%. More importantly, these membranes showed no performance deterioration throughout 50 filtration cycles, with only a slight increase in permeance of 19.3% over a 38-day testing period. Thus, this work presents a novel solution for fabricating MXene composite membranes with low swelling, minimal defects, and high stability, enhancing its potential in the field of water and wastewater treatment.

A feasibility study of hybrid forward osmosis-solar evaporation process using melamine sponge loaded with polypyrrole (PPy@MS) solar evaporator for desalination of brackish water

The application of the osmotic pressure-driven forward osmosis (FO) process is limited due to the high costs for regeneration and replacement of draw solution. A hybrid FO-solar evaporation (SE) hybrid process was systematically investigated to produce fresh water from desalination of brackish water. The melamine sponge loaded with polypyrrole (PPy@MS) composite material was synthesized by loading light-absorbing polypyrrole (PPy) into a network of melamine sponge (MS) substrates. As a solar evaporator, PPy@MS material showed high light absorption, water evaporation, and anti-pollution abilities in the FO-SE process. Feasibility for operating the hybrid desalination process was studied in terms of solar evaporation rate, salinity tolerance, hydrophilicity, and mechanical strength of PPy@MS, and desalination performance, including water flux, ion removal, reverse salt flux, and membrane fouling. Characterization results indicated that PPy@MS performed a high interfacial molecular transformation, solar energy accessing ability, salt-tolerance, and mechanical stability in a long-term FO-SE operation, achieving an evaporation rate up to 2.80 kg·m−2·h−1 (1 sun, 1 h) and ion removal rate of 99.9 %. A maximum evaporation flux of 17.4 L·m−2·h−1 was monitored in the FO-SE process using 2 M NaCl as the draw solution (FO film area: 5 cm2). Solar-driven evaporation via PPy@MS was able to assist the continuous operation of the FO-SE process with high water flux. This work proposes a novel sustainable hybrid FO-SE technology for FO desalination of brackish water and other saline water bodies.

Systematic investigation of MAX phase (Ti3AlC2) modified polyethersulfone membrane performance for forward osmosis applications in desalination

The current work presented an in-depth investigation of the design and fabrication of thin film membranes for desalination applications by forward osmosis (FO). This includes manipulating the substrate membrane structure aiming to optimize the final thin film composite membrane characteristics. In this context, the MAX phase (Ti3AlC2) as a 2D material has been harnessed to impart novel desirable traits on the prepared membrane. MAX phase has been impregnated in two disparate concentrations and three different scenarios including the substrate membrane and the polyamide layer in both the aqueous and organic phases during the interfacial polymerization. Membranes were comprehensively characterized by a series of experimental tools and methodologies including Atomic Force Microscopy, Scanning Electron Microscopy, Contact Angle, Fourier-transform infrared spectroscopy, pore size and porosity. Results disclosed that substrate membrane structure has a pivotal impact on final TFC/TFN membrane performance. Besides, the MAX phase (Ti3AlC2) could significantly enhance the morphological characteristics of the membrane and ultimately the performance in terms of water flux and reverse salt flux based on the content and the way impregnated. The permeation properties of the composite membranes were significantly superior to the pure PES membrane and the mean pore size also increased with the addition amount of MAX phase (Ti3AlC2) increased.

Dynamic relationship between membrane fouling and reverse diffusion of inorganic draw solutes in forward osmosis

Both membrane fouling and reverse diffusion limit the application of forward osmosis (FO), and the combined effects further decrease water generation. Herein, the effects of typical inorganic draw solutes (DSs) were investigated on the dynamic relationship between membrane fouling from two organic pollutants and reverse diffusion. The formation of a membrane fouling layer decreased the amount of Ca2+ ions reverse-diffusing from a CaCl2 DS and increased the amount of NH4+ ions reverse-diffusing from a NH4Cl DS. When sodium alginate was used as the feed solute, reverse-diffused ions from the CaCl2/NH4Cl DS resulted in the formation of a three-dimensional network structure, further exacerbating membrane fouling. Moreover, greater reverse diffusion of NH4+ from the NH4Cl DS resulted in more membrane fouling in comparison with the CaCl2 DS (i.e., water recovery of 246.4 ± 4.7 g), resulting in a lower water recovery value of 151.4 ± 10.6 g. During the filtration of humic acid, the membrane fouling layer caused by the CaCl2 DS led to the formation of a cake filtration layer that was more severe than that formed when the NH4Cl DS was used. This study provides a reliable basis for draw solute optimization to extend the application of FO systems.

Rejection of organic micropollutants from greywater with forward osmosis: A matter of time

Forward osmosis (FO) has popularized lately due to its lower fouling propensity, higher pollutant rejection, and potentially lower energy consumption than other membrane technologies. Greywater (GW) is a good candidate for FO treatment for its further reuse due to its lower organic and solids content than other wastewater streams, but it contains organic micropollutants (OMP) that might pose a risk for its reuse. Seawater (NaCl) is widely used as draw solution, but the use of fertilizers instead offers the advantage of applying the diluted draw solution for irrigation. This study evaluated the performance of FO for GW treatment focusing on OMP rejection, by means of tests with fertilizers or NaCl as draw solutions and deionized water or GW as feed solutions. The main GW constituents were well rejected, except for sodium, which diffused to the draw solution. Excellent OMP rejection was obtained (>95% in most cases, average 98.5% rejection at the end of the experiments), which was influenced by experimental conditions and OMP properties. Highest rejections were observed for negatively charged OMP and for neutral/positive charged OMP with large molecular weight. Feed type and contact time between feed and draw solutions had the biggest influence on OMP rejection, which decreased over time and by using GW instead of deionized water as feed solution. The diluted draw solution proved safe for irrigation water reuse purposes although sodium content could be of concern. Further studies on the contact time between the solutions are required to foster further applications of FO, as it clearly influenced the rejection of OMP, aspect that is crucial for safe water reuse applications.

Source-separated urine treatment based on forward osmosis technology: Performance, applications and future prospects

Human urine has been historically regarded unwanted in wastewater treatment plants due to its abundant and imbalance nutrients for biological treatment processes. Recently, comprehensive understanding and investigation of urine has received increasing interests to turn it into valuable resources for urine-based fertilizer production. This review aims to comprehensively evaluate the performance of forward osmosis (FO) membrane technology for urine treatment for water and nutrients recovery. Among different urine-based FO approaches, the fertilizer driven forward osmosis (FDFO) consumes less specific energy and produces higher valuable products comparing with other urine treatment technologies. But to remove micropollutants in urine, FDFO should couple with Advanced Oxidation Processes (AOPs). Moreover, the combination of FO and membrane distillation (MD) has great potential for completely recovering nutrients and water from human urine. In addition, current challenges and limitations of urine-based FO applications are discussed. Future perspectives on the development of urine-based FO applications are also proposed. It is suggested that further research should focus on developing high performance FO membranes to maximize the water flux as well as recovering nutrients and reject micropollutants in urine. Besides, there is also a great need to develop ideal environmentally friendly draw solutions to accelerate the urine-based FO applications. Above all, a comprehensive life-cycle impact assessment is needed before the large-scale application.

Preparation of Thin Film Composite (TFC) Membrane with DESPs Interlayer and Its Forward Osmosis (FO) Performance for Organic Solvent Recovery.

To explore the application of forward osmosis (FO) technology in the organic solvent recovery field, we prepared a new solvent-resistant triple layer thin film composite (TFC) membrane on the PI (polyimide) substrate. The deep eutectic supramolecular polymers (DESPs) interlayer was constructed on the substrate to improve the separation performance and solvent resistance. DESPs interlayer was formed by mixing and heating with cyclodextrin as the hydrogen bond acceptor and L-malic acid as the hydrogen bond donor. The chemical changes, surface property and morphology of the composite membrane with DESPs interlayer were characterized. The separation performance and stability of the triple layer composite membrane in organic solvent FO were studied. For the monascorubrin-ethanol system, the permeation flux of TFC/DESPs5-PI membrane could reach 9.51 LMH while the rejection rate of monascorubrin was 98.4% (1.0 M LiCl/ethanol as draw solution), which was better than the pristine membrane. Therefore, this solvent-resistant triple layer composite FO membrane has good potential for the recovery of organic solvents.

Support-free multi-walled carbon nanotubes-based membrane for forward osmosis applications

This study aims to fabricate a thin-film composite membrane with high water flux and low reverse solute flux for the application in a forward osmosis (FO) system. Instead of using traditional non-woven fabric or polymer materials, multi-walled carbon nanotubes (MWCNTs) layers prepared via the vacuum filtration method to reinforce the membrane are fabricated. In this work MWCNTs are modified by the mixture of polydopamine (PDA) and polyvinyl alcohol (PVA) to enhance the mechanical strength and hydrophilicity of the membrane, which is denoted as PVAm pCNTn. Finally, a polyamide (PA) active layer, used as molecular selection, is synthesized on the PVAmpCNTn film using the interfacial polymerization method, which is assigned as PVAmpCNTn-PA. Experimental results show that PDA and PVA improve adherence among the MWCNTs, strengthening the tolerance and increasing hydrophilicity of the membrane. Membrane performance is also affected by the amount of PVA(m) and PVA(n), and thickness can be controlled by adopting various amounts of MWCNTs suspension during the vacuum filtration process; the thinner membrane results in higher water flux because of lower flow resistance. In addition, the PVA concentration influences the pore size distribution and configuration within the membrane, as a result, affects the FO performance. The best FO performance are achieved by PVA0.25pCNT3-PA, with a water flux of 30.16 L m−2 h−1 and reverse solute flux of 9.34 g−2 h−1. The excellent FO performance and the simple process used in this study indicate the great potential of this work in the FO application.

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.

State-of-the-Art of Forward Osmosis Technology: Prospects and Limitations

Forward osmosis is considered as an emerging technology that can compete with existing methods of desalination, purification and concentration of natural and wastewater on the global water market. This review presents possible applications of forward osmosis, technological schemes and the most striking case studies. The issues of forward osmosis membranes development and improvement, composition and regeneration of draw solutions, membrane fouling are considered. Special attention is paid to the problems arising during forward osmosis operation, to energy and economic assessment of new technology. Conclusions are drawn about the status of the commercial implementation of forward osmosis and the main barriers that stand in the way of its development.

Characterization of a Model Bioreactive Membrane for the Simultaneous Separation and Hydrolysis of Lipopolysaccharides

The design of functionalized selective layers to develop novel membranes is essential to provide potential solutions that meet the continuously growing demand of providing safe water. Herein, we present the interfacial response of an enzymatic thin-film composite (E-TFC) membrane displaying dual functionality and fabricated as a proof-of-concept for both efficient lipopolysaccharide (LPS) separation and ester bond hydrolysis. The enzymatic membrane model was constructed by employing lipase b from Candida antarctica (CALB) covalently coupled via chemically activated bisepoxide groups onto the surface of the di-block copolymer polystyrene-b-poly(4-vinyl pyridine) (PS-b-P4VP) layer. Our results show a complete rejection of size-excluded LPS molecules when using the fabricated E-TFC membrane in a forward osmosis (FO) application. Moreover, the immobilized enzyme was able to retain 97% of its enzymatic activity when using 4-nitrophenyl acetate (pNPA) and up to 74% to liberate free fatty acids from LPS molecules within the feed side of the FO system. This work provides fundamental insights into new emerging functional biomaterials that find applications in hybrid catalytic filtration processes that also selectively remove LPS molecules from water sources.

On performance and anti-fouling properties of double-skinned thin film nanocomposite hollow fiber membranes in forward osmosis system

This study involves the preparation of a double-skinned thin film composite (TFC) and thin film nanocomposite (TFN) hollow fiber (HF) membrane for forward osmosis (FO) applications. The porous substrate consisted of a Polyvinyl chloride (PVC) / Polycarbonate (PC) blend HF membrane. Interfacial polymerization (IP) was then applied to coat a polyamide (PA) layer on the lumen surface and the porous substrate's outer surface. In addition, the impact of the outer PA active layer and the addition of nanoparticles to the outer selective layer on the FO flux and internal concentration polarization (ICP) were studied. By adding the second active layer to the substrate, water flux, reverse salt flux and ICP decreased. Also, the decline of water flux decreased over time due to the fouling agent. To compensate for the decrease in water flux in the double-skinned membrane, graphene oxide (GO) nanoparticles with 0.05% and 0.1%wt were added to the outer active layer. Addition of 0.1%wt graphene oxide nanoparticle to the outer active layer can help to improve water flux about 78% without spoiling the reverse salt flux. Moreover, the performance of double-skinned membranes against osmotic dilution process for oily wastewater treatment was investigated. The findings of this study demonstrated that the novel double-skinned TFN HF membrane exhibited high FO performance with low ICP and fouling.

A novel Solution-Diffusion-Flory-Rehner model to predict flux behavior during forward osmosis with thermo-responsive hydrogel as draw agent

Although hydrogels as excellent draw agents have been extensively investigated, the relationship between the driving force of hydrogel and mass transfer behavior during forward osmosis (FO) remains unclear. The hydrogel-driven FO requires a mass transfer model to clarify its driving mechanism, yet no model was available at present. In the current study, a water flux model driven by thermal-responsive hydrogel was first developed by coupling solution-diffusion model and Flory-Rehner model (SDFR). Considering the diffusion characteristics of hydrogel, a redefined parameter DH corresponding to water diffusion coefficient in hydrogel matrix was introduced to the SDFR model. The validity of the model and DH were verified by comparing experimental water flux data for different concentrations of feed solution with the corresponding simulating results from SDFR model. The SDFR model successfully predicted the flux behavior of FO under wide varieties of operating conditions. Furthermore, the existence of internal concentration polarization phenomenon in hydrogel-driven FO was unveiled by modeling the pressure distribution across FO membrane, and its effect on flux behavior was quantified. The SDFR model was also employed to design a novel ionic thermal-responsive hydrogel with better FO performance. The new insights gained from the SDFR model in this study will help to develop more efficient FO applications with hydrogel-based draw agents.

Research Progress of Water Treatment Technology Based on Nanofiber Membranes.

In the field of water purification, membrane separation technology plays a significant role. Electrospinning has emerged as a primary method to produce nanofiber membranes due to its straightforward, low cost, functional diversity, and process controllability. It is possible to flexibly control the structural characteristics of electrospun nanofiber membranes as well as carry out various membrane material combinations to make full use of their various properties, including high porosity, high selectivity, and microporous permeability to obtain high-performance water treatment membranes. These water separation membranes can satisfy the fast and efficient purification requirements in different water purification applications due to their high filtration efficiency. The current research on water treatment membranes is still focused on creating high-permeability membranes with outstanding selectivity, remarkable antifouling performance, superior physical and chemical performance, and long-term stability. This paper reviewed the preparation methods and properties of electrospun nanofiber membranes for water treatment in various fields, including microfiltration, ultrafiltration, nanofiltration, reverse osmosis, forward osmosis, and other special applications. Lastly, various antifouling technologies and research progress of water treatment membranes were discussed, and the future development direction of electrospun nanofiber membranes for water treatment was also presented.

Self‐Assembly in “Matrix‐Free” Functionalized Boron Nitride Sheets as Free‐Standing Thin Film Sieves for Stable Forward Osmosis and Robust Dye Removal Applications

AbstractHerein, a facile “matrix‐free” thin film membrane strategy is reported that exploits polymer brushes grafted hydroxyl‐functionalized hexagonal boron nitride nanosheets (h‐BNOH) toward forward osmosis desalination and dye rejection application. The functionalized nanosheets are characterized using Fourier transform infrared spectroscopy (FTIR), high‐resolution transmission electron microscopy (HRTEM), X‐ray diffraction (XRD), Nuclear magnetic resonance (NMR), UV–visible spectrophotometry, and thermogravimetric analysis (TGA). Covalently functionalized nanosheets of poly methyl methacrylate (PMMA) termed as boron nitride grafted PMMA (BN‐g‐PMMA) obtained via RAFT polymerization are deployed toward “matrix‐free” nanocomposite membranes. The membranes exhibit ≈5260 L /m−2 h−1 at a moderate pressure of 0.21 MPa in cross‐flow mode and a 70% of flux retention ratio against bovine serum albumin as protein foulant. The matrix‐free membranes exhibit ≈93% salt rejection for NaCl and >99% rejection for MgCl2 and Ca(NO3)2·4H2O for 2000 ppm draw solution (water TDS benchmark for domestic purifiers) while 90% NaCl, and >96% rejection for MgCl2 and Ca(NO3)2·4H2O for 5000 ppm draw. In simulated domestic water salinity, 97.8% rejection is observed for 2000 ppm and 94.5% for 5000 ppm draw solution, respectively. The matrix‐free membranes also achieve almost 100% dye rejection for eight model dye pollutants at 1 ppm and >96.6% for 10 ppm concentrations, respectively.