Forward osmosis using a nanoparticle slurry draw solution with DC-field-driven separation

Slaughterhouse wastewater (SW) contains high organic matter and nutrients, requiring sustainable treatment methods like forward osmosis (FO). This study evaluates the performance of four membranes: M1 (cellulose triacetate), M2 (M1 with carbon nanotubes), M3 (cellulose triacetate/diacetate), and M4 (M3 with carbon nanotubes) for treating SW. It reports the first-time use of CNTs in a hybrid membrane (CTA/CDA) for FO applications. Characterization showed that CNTs improved the mechanical and structural properties of M1, increasing the contact angle from 68 to 75°C and roughness from 499.59 to 542.57nm. However, for M3, the addition of CNTs in M4 decreased the contact angle from 88 to 77° and roughness from 773.088 to 620.001nm. While CNTs enhanced hydrophilicity, they reduced permeability and fouling resistance due to fewer water transport channels. FTIR analysis revealed distinct stretching patterns correlating with variations in contact angles and membrane performance. The evaluation of membranes in forward osmosis (FO) comprised four phases. In Phase 1, membrane M3 excelled with 91.6% water removal and 0.32 LMH flux using 0.5M MgCl₂, outperforming M4 at 80.84% and 0.28 LMH due to Mg²⁺ ion accumulation in M4. Phase 2 confirmed M3's superiority with MgCl₂ among the four 0.5M draw solutions. In Phase 3, M3 demonstrated an enhancement of 93.76% and 0.33 LMH with a 1M solution., while M4's performance reached 90.91% with 1M NH₄HCO₃. Overall, low water flux was attributed to the lower circulation rates of feed and draw solutions. Phase 4 showed that M3's water flux supported the growth of Dunaliella salina, while M4's lower-salinity flux hindered it. This study explores the potential of hybrid membranes reinforced with carbon nanotubes (CNTs) for forward osmosis in treating slaughterhouse wastewater. It reveals a gap in data regarding CTA and CDA blends with CNTs, marking this as a new research area. The findings indicate that CNTs do not enhance the performance of hybrid membranes for this application; therefore, cost-effective membrane (M3) using recyclable solutes like NH₄HCO₃ present a promising solution for sustainable wastewater treatment.

Hybrid desalination systems that combine osmotic and thermal driving forces offer a promising route to improve water recovery and energy efficiency for high-salinity feedwaters where conventional processes face limitations. This study presents a comprehensive mathematical modeling framework and performance analysis of a hybrid forward osmosis-membrane distillation (FO-MD) system for seawater desalination. The novel contributions include: (1) a coupled heat, mass, and solute transport model that explicitly accounts for concentration polarization, temperature polarization, reverse salt flux, and their dynamic interactions through the draw solution loop; (2) a quantitative assessment of the synergistic regeneration effect, showing how MD maintains draw solution concentration and stabilizes FO performance over time; (3) systematic evaluation of parameter sensitivity to polarization effects; and (4) comparative energy analysis quantifying specific energy consumption relative to standalone processes. Model predictions were validated against published experimental data, showing good agreement for both FO and MD fluxes (R2 > 0.94). The MD flux increased from approximately 2-3 LMH at 30 °C to 17 LMH at 50 °C, confirming vapor pressure enhancement. FO water flux increased significantly with draw solution concentration from 0.2 to 1.1 M due to higher osmotic pressure differences. Time-dependent simulations of the integrated FO-MD system showed that MD regeneration reduces draw solution dilution by 60% compared to standalone FO, maintaining FO flux approximately 43% higher after 6 h of operation. Sensitivity analysis revealed that FO predictions are moderately sensitive to mass transfer coefficients (6-9% flux change for 20% parameter variation), while MD shows lower sensitivity to heat transfer coefficients (3-5%). Energy analysis indicates that FO-MD hybridization reduces thermal energy consumption by 15-40% compared to standalone MD, with specific energy consumption of 382 kWh/m3 (40.2 kWh/m3 primary energy equivalent) when using low-grade heat. The obtained results demonstrate that FO-MD hybridization enhances water recovery and operational stability compared to standalone processes, supporting its potential for energy-efficient desalination of high-salinity brines and industrial wastewaters where low-grade heat is available.

Continuous pilot-scale operation using FO membranes to concentrate municipal wastewater with artificial seawater as draw solution

Pressure retarded osmosis (PRO) is a green technology for harvesting Gibbs free energy from mixing solutions with different salinity gradients. Although lab-synthesized membranes showed high PRO performance, there is no available flat-sheet industrial-scale PRO membrane production. Most of the previous studies have focused on enhancing the power density of the PRO process by using a hypersaline draw solution that potentially causes severe internal and external concentration polarization (ICP and ECP) and limits achievable performance. Using the most accessible resources – seawater and commercially available membranes – can be a more practical way to develop a large-scale PRO plant. However, only a limited number of studies have evaluated the PRO performance under such realistic conditions. In our study, we compared the PRO performance of some commercial FO and RO membranes. We observed that, at an elevated feed velocity and temperature, the RO membrane had a significant enhanced water flux and power density. Due to turbulent flow at a high feed velocity and low viscosity at a high feed temperature (30 °C), the RO membrane was able to perform at low concertration polarization, hence maximum power density (5.3 W/m 2 ) could be obtained at half the osmotic pressure (15 bar). • Seawater and commercial RO and FO membranes were used for PRO • An elevated feed velocity and temperature resulted in high power density • Commercial RO membranes outperformed FO membranes in the PRO tests • 5.3 W/m 2 was achieved at 15 bar using a commercial RO membrane

The Smackover Formation brines in southern Arkansas contain a large quantity of lithium, a critical resource for electric vehicle batteries and the global energy transition. To extract the lithium, efficient downstream enrichment technologies are urgently needed. Methods for direct lithium extraction are being explored, followed by further purification and concentration of the lithium salt solution, such as using reverse osmosis, which is energy intensive. Here we use reduced graphene oxide (RGO) membrane-based forward osmosis (FO) as an environment-friendly and near zero-energy input method to concentrate lithium brine. In the FO tests, a saturated NaCl solution serves as a draw solution and either a dilute lithium nitrate (LiNO3) solution (50.4 mM) or an artificial lithium brine (1.00 M NaCl + 12.0 mM LiNO3) as a feed solution, where LiNO3 is selected to mimics the typical LiCl component in lithium brine. Because nitrates have a unique absorption feature at ∼300 nm, their concentrations in both the feed and draw solutions can be monitored by a facile ultraviolet-visible (UV-Vis) absorption spectral method. For the dilute LiNO3 solution, a rejection rate is determined to be 97.9 ± 0.1%, with a water flux of 6.2 ± 0.2 L/hm2. For the artificial brine, a rejection rate of 88.4 ± 0.1% and a water flux of 5.0 ± 0.2 L/hm2 are observed. With further optimization, this forward osmosis approach could provide a more energy-efficient method for lithium salt enrichment, supporting sustainable lithium extraction from Smackover brines.

Abstract The detection of trace antibiotics in aquatic environments poses a critical global challenge, threatening both ecological safety and public health. Forward osmosis (FO) membrane separation technology has emerged as a highly efficient approach for purification of trace antibiotics, characterized by high treatment efficiency and low energy consumption. However, challenges inherent to the recycling of draw solutions restrict the development of FO technology. Herein, we report the synthesis and application of a novel CO 2 -responsive SiO 2 @PDEA nanocomposite as a highly recyclable particulate draw solution. This system leverages CO 2 /heat-triggered reversible switching between hydrophilicity and hydrophobicity to enable facile recovery. The 6 wt% SiO 2 @PDEA solution leads to a significantly enhanced water flux ( J w ) to 5.31 LMH (PRO mode), a threefold increase over bare SiO 2 . Crucially, the ratio of reverse solute flux ( J s ) to J w was minimized to 0.015 g/L, providing a substantial cost advantage over inorganic salts. The efficiency of this approach enabled a threefold concentration of tetracycline. Furthermore, the solution demonstrated outstanding cyclic stability with a solute recovery rate consistently exceeding 99% via mild thermal stimulation. These findings demonstrate that SiO 2 @PDEA is an exceptionally efficient, sustainable, and cost-effective draw solution with substantial potential for the practical remediation of trace antibiotic-containing wastewater.

• Textile wastewater was treated by simultaneous forward osmosis and reverse osmosis. • FO draw solution was continuously concentrated by RO. • Chemical oxygen demand and total organic carbon were rejected above 99%. • Simultaneously, clean water was obtained as the reverse osmosis permeate. The concerning and abundant textile wastewater can be treated by forward osmosis (FO) in order to reduce its volume and simultaneously recover clean water. However, the productivity of FO depends on the concentration of the draw solution that is used. In this work, a simultaneous application of FO and reverse osmosis (RO) is proposed. The HFFO14® FO membrane (Aquaporin, Denmark) was employed to concentrate a real textile wastewater, whereas the SW30-2540 (DuPont, USA) RO membrane was employed to simultaneously regenerate the draw solution, which consisted in a 0.7 M NaCl solution, and to obtain a clean water stream. The concentration of the textile wastewater increased until 90% water recovery was achieved. The rejection values obtained for the chemical oxygen demand and total organic carbon were in the range 99 – 100%. Afterwards, the previously concentrated textile wastewater was again processed until a volume concentration factor of 16.5 was reached. Stable values of permeate flux (around 4 L/h·m 2 ) were obtained in the FO process, whereas the reverse osmosis step permitted the maintenance of a stable conductivity in the draw solution and provided clean water as permeate.

MD simulations of UCST liquid-liquid phase separations of [Hbet][Tf2N]/Water mixtures

Repurposing usage of oil refinery wastewater with retrofitted desalination technology necessitates the optimization of a forward osmosis (FO) technology. Herein, factors such as draw solution concentration (DS-C) and feed and draw solution flow rates (FS-FR, DS-FR) play significant roles. In this study, the individualistic and interaction effects of these factors were explored to ascertain the FO performance. The effects of these operating factors, DS-C (20-50 g/L), DS-FR (7.5-9.4 L/h), and FS-FR (7.5-9.4 L/h), and their interactive effects on the permeation flux and rejection of Cl-, SO42- and CO32- from oil refinery effluent, were studied using the Box-Behnken design (BBD) of response surface methodology (RSM). Statistical models were developed to optimize the operating conditions. The analysis of variance and the developed response models were used to evaluate the data at a 95% confidence level. Three confirmatory runs were conducted based on the optimum conditions (FS-FR: 9.2 L/h; DS-FR: 9.4 L/h; DS-C: 32.6 g/L). At a desirability of 81%, average rejections of 94.59 ± 0.32% for CO32- and 100% for SO42- were obtained. Average Cl- enrichment was 35.5 ± 5.15% and average permeation flux of 3.64 ± 0.13 L/m2 h were achieved, suggesting that RSM was a suitable tool for optimizing FO for desalinating the effluent. In addition, the average recovered permeation flux of 86.01 ± 2.66% demonstrated the effectiveness of the FO membrane after cleaning.

This study examines the application of mining effluents as feed solutions in a bench scale pressure retarded osmosis (PRO) system for energy generation and the prospect of water recycling or safe discharge to the environment. Effluents were characterized and pretreated by ultrafiltration (UF) and nanofiltration (NF) prior to PRO. The PRO process was then conducted over 6 h in a cross flow flat plate cell with an effective membrane area of 34 cm2, a hydraulic pressure of 12.4 bar and a 3M ammonium carbonate (NH4)2CO3 as draw solution. Effluent 1 contained ions such as Cl− (539 mg/L), NO3− (585 mg/L), SO42− (3000 mg/L), Na+ (560 mg/L), and Mg2+ (656 mg/L), with a total dissolved solids (TDS) concentration of 5400 mg/L, chemical oxygen demand (COD) of 136 mg/L, total organic carbon (TOC) concentration of 3.5 mg/L, and acidic pH of 3.8, while effluent 2 was highly dominated by Cl− (32,100 mg/L), NO3− (9720 mg/L), SO42− (6512 mg/L), Na+ (14,306 mg/L), and Mg2+ (5336 mg/L), had a TDS concentration of 73,315 mg/L, COD of 8100 mg/L, TOC concentration of 10.2 mg/L, and pH of 7.4. These physiochemical properties indicated a significant potential of fouling and scaling which necessitated the appropriate pretreatments. It was shown that integrating UF and NF pretreatments was highly effective in refining the quality of effluents with a significant removal efficiency of above 90% for ions and heavy metals by NF, led to fouling mitigation, higher and more stable power density as well as potential water reuse or safe environmental discharge. The achieved water fluxes and power densities were 54 L/m2h and 18.6 W/m2, for effluent 1, and 38 L/m2h and 13 W/m2, for effluent 2, respectively. The outcome of this study is applicable for the mining sector especially in remote areas with the potential for water and energy recoveries to contribute to more sustainable mining operations.

Forward osmosis (FO) has emerged as a highly attractive separation technology owing to its potential low-grade energy consumption and versatile applications. However, a significant gap remains in understanding its performance under dynamic conditions. This study investigates the dynamic performance of the FO process using NaCl and NH4HCO3 draw solutes. This study entails a well-established FO water flux model alongside dynamic molar balances to predict the dynamic profiles of key variables including water flux, salt back-diffusion, cumulative feed and permeate volumes, and concentration/dilution rates. The membrane parameters are evaluated considering the continuous decrease in concentration gradient across the membrane throughout the operating period. These parameters are calculated through a model of the specific salt back-diffusion formulated using Pyomo-AML. Model predictions were compared to experimental data over 20h at 1-min intervals, resulting in mean absolute errors ranging from 0.13 to 3.55% for the studied variables.

Thermally responsive ionic liquids (ILs) exhibit liquid-liquid phase separation into a water-rich (WR) and ionic-liquid-rich (ILR) phase when heated above a lower critical solution temperature (LCST). This phase behavior has been leveraged for applications ranging from forward osmosis (FO) desalination, where the IL acts as a draw solute, to refrigeration and dehumidification cycles, where the IL acts as a liquid desiccant. While significant effort has been devoted to characterizing the thermodynamic and thermophysical properties of LCST ILs, their phase separation kinetics have not been investigated. In this work, we describe the macroscale phase separation kinetics (phase separation time) by gleaning insight into the microscale colloidal behavior of aqueous mixtures of four different materials, P4444TFA (tetrabutylphosphonium-2,4-trifluoroacetate), P4444DMBS (tetrabutylphosphonium-2,4-dimethyl-benzenesulfonate), N4444Sal (tetrabutylammonium salicylate), and P4444Sal (tetrabutylphosphonium salicylate) as a function of IL concentration at a separation temperature of 70 °C. We report the discontinuous microscale size distributions for each material and correlate their theoretical settling velocities to experimental phase separation times. The results indicate that a simple Stokes' law model can predict the phase separation time within reasonable accuracy. Overall, this work lays the foundation for understanding the micro- to macroscale phase separation behavior and kinetics of LCST ILs for various water-energy applications.

Osmotic distillation (OD) was evaluated as a gentle, non-thermal route for partial removal of ethanol from beer using an in-house hydrophobic flat sheet polyvinylidene fluoride (PVDF) membrane to produce a healthy beverage. A 16 wt.% PVDF membrane prepared by non-solvent induced phase inversion was mounted in a transparent acrylic cell that separated circulating feed and NaCl draw solutions at ambient temperature and zero transmembrane pressure. Membrane characterization by SEM, FTIR, and water contact angle confirmed an asymmetric porous structure, chemically intact PVDF, and stable hydrophobicity (θ ≈ 92°), suitable for vapor phase mass transfer without wetting. Ethanol-water model solutions (5 and 8 % v/v) and three commercial beers (Budweiser, Kingfisher Strong, and Kingfisher Lite) were treated with 2-3 M NaCl draws, and ethanol concentrations in both circuits were monitored by refractive index measurements calibrated with matrix-matched standards. For model solutions, the feed ethanol content decreased from 5.0 to ~2.5% and from 8.0 to 3.6%, corresponding to removal efficiencies of ~50% and ~55%, respectively, consistent with the higher vapor pressure driving force at elevated initial concentrations. For beers, single pass OD with 3 M NaCl achieved ethanol reductions of ~52 % (Budweiser), ~53 % (Kingfisher Strong), and ~58 % (Kingfisher Lite) over 24 h, with no evidence of salt passage or liquid breakthrough. These results demonstrate that a simple flat-sheet OD configuration can reproducibly deliver reduced alcohol beers under mild operating conditions and

Dual-functional ionic liquids exhibiting upper critical solution temperature behavior and antibacterial activity as draw solutes for forward osmosis

Integrated in-situ electrochemical-membrane process for ammonia valorization and sustainable water reuse.

Nanoplastics-mediated interfacial processes controlling perfluorooctanoic acid transport in forward osmosis.

Alternated tangential flow millifluidic devices for forward osmosis : mitigation of concentration polarization

Donnan dialysis (DD) is a promising approach for selectively recovering ammonium ions from wastewater, owing to its simplicity and low energy consumption. However, the role of ion sorption and desorption in cation exchange membranes (CEMs), particularly interactions between ammonium ions (NH4 +) and competing ions (e.g., sodium Na+), has often been overlooked. Our experimental results revealed a shift in the Donnan equilibrium caused by the preoccupied counterions in the CEM. For example, when the feed and draw solutions were in a 1:1 concentration ratio, the expected ammonium recovery efficiency was 50%. However, the NH4Cl-presoaked membrane resulted in an increase of 19.1 ± 0.5% in the solution NH4 + concentration and a decrease of 18.8 ± 0.6% in the Na+ concentration. Conversely, the NaCl-soaked membrane showed an 18.9 ± 1.6% reduction in NH4 + and a 23.0 ± 1.3% increase in Na+. The difference indicated that the ion exchange capacity of the membrane and counterion uptake could shift the equilibrium of the DD process. We further analyzed the process kinetics and developed a nonsteady-state model incorporating ion sorption capacity to describe the behavior. Our results confirmed that presoaked ions shifted the final DD equilibrium, potentially due to differences in their affinity and geometry. To summarize, this study provides new insights into the mechanisms of Donnan dialysis by accounting for ion sorption and offers insights for the design of more efficient and effective separation processes for ammonium recovery.

Anaerobic fermentation has emerged as an effective method for carbon recovery in wastewater treatment, especially for sewage sludge. However, the first supernatant from primary settling tanks, despite containing more organic matter than sludge, is rarely used due to its low total organic carbon (TOC) concentration—typically only several tens of mg/L. For efficient methane fermentation, the TOC must be concentrated to at least 600 mg/L. Conventional concentration methods involving phase transitions, such as distillation, are energy-intensive. Forward osmosis (FO), a low-energy process that avoids phase changes, offers an alternative; however, conventional FO membranes concentrate not only organic matter but also inhibitory ionic species, such as Na + , K + , and SO₄ 2− . This study proposes the use of a loose FO membrane and a high–molecular weight draw solute (Pluronic 17R-4, Mw = 2700) to selectively concentrate organic matter while allowing ion leakage. Loose FO membranes cannot effectively reject small ions, such as Na + and Cl − , thus requiring draw solutes with higher molecular weights. Pluronic 17R-4, a thermoresponsive poloxamer, was employed as a high-molecular-weight draw solute. Poloxamers exhibit thermal phase separation, facilitating regeneration using waste heat a promising energy-efficient FO approach. The TOC of the first supernatant was successfully concentrated over 100-fold, reaching more than 2000 mg/L. Methane fermentation of the concentrated solution resulted in successful biogas production, whereas a conventional FO membrane led to inhibition due to ion accumulation. This approach demonstrates the feasibility of FO with loose membranes for low-energy, high-efficiency carbon recovery from dilute wastewater streams. • Loose FO membrane concentrated TOC over 100-fold from sewage supernatant. • Ion leakage through loose FO membrane reduced fermentation inhibition. • Pluronic 17R-4 enabled efficient draw solute recovery via phase separation. • Methane was successfully produced from FO-concentrated sewage supernatant. • Loose FO membrane outperformed normal FO in flux and fermentation compatibility.