Forward Osmosis Water Flux Research Articles

Coupling of photovoltaic thermal with hybrid forward osmosis-membrane distillation: Energy and water production dynamic analysis

This study proposes a novel solar photovoltaic thermal (PVT)-driven forward osmosis (FO) and membrane distillation (MD) system for desalinating brackish water, addressing water scarcity issues by combining the advantages of FO's low operating cost with MD's ability to treat hypersaline water. A physics-based dynamic model was developed for the system, and the model equations were discretized and solved using an open-source algebraic modeling language. Model validation involved verifying the consistency of outputs between successive unit operations and conducting sensitivity analysis by varying one operating condition at a time. The analysis considered varying weather conditions while maintaining constant operating conditions. Increasing the flow rate of brackish water (cooling fluid) from 19.79 to 59.38 kg/h improved thermal efficiency by 28.7 %; however, FO and MD water fluxes decreased by 1.12 LMH and 7.77 kg/m2/h, respectively. Peak thermal efficiency (81.2 %) was achieved at the highest flow rate. Incorporating heat transfer analysis into FO models goes beyond the common focus on mass transfer, allowing for a more comprehensive understanding of energy dynamics within the system. Both FO and MD water fluxes improved with irradiance and ambient temperature but decreased with cooling fluid flow rate and wind velocity. Increasing feed concentration to 10,000 mg/l reduced water flux by 0.66 LMH, and for each 0.5 M increase in draw solution concentration, FO water flux increased by >10 LMH. Compared to MD water flux, FO water flux is more sensitive to changes in concentration than to changes in weather conditions.

Pectin recovery from apple pomace by forward osmosis – Assisted technology

This study evaluates the performance of forward osmosis (FO) to concentrate and dewater apple pomace extract for subsequent pectin recovery. After pretreatment by sieve filtration and centrifugation, the FO water flux during real apple pomace extract concentration was 7.8 L m−2·h−1 and was comparable to the FO process for a one-component model pectin solution. However, due to fouling, at 75% water recovery, up to 70% flux decline was observed. Osmotic backwashing using a spent draw solution as the osmotic agent was effective and could completely restore the water flux (ca. 100% flux recovery) after multiple filtration cycles. A comprehensive techno-economic assessment was also conducted to demonstrate significant reduction in capital investment and operating cost when applying FO for concentrating apple pomace extract prior to pectin recovery. The investment payback period was shortened from over 5 to 2 years, at 80% water recovery. Results in this study highlight the utility of FO to replace the traditional evaporation method for enhance the economic viability and environmental friendliness of pectin recovery.

Approaching ratio as a guideline for substrate design of forward osmosis membranes

Forward osmosis (FO) has been proposed as an ecologically friendly and low carbon footprint technology for concentrating enriched lithium brine from the salt lake using freely available MgCl2 onsite as the draw. In this process, Li+ concentration is raised from a few hundred mg/L to 20-30 g/L (Li+) before precipitation of Li2CO3. To allow FO technology a wide margin in competing with other concentration technologies, it is highly desirable to develop a simple, low cost method to fabricate FO membrane. Besides, due to both feed and draw solutions being of high salinity, FO membranes should also have a defect-free polyamide (PA) separation layer and a low structural parameter (S) substrate. This paper presents a simple guideline called approaching ratio (α) to adjust the substrate pore morphology based on a ternary polysulfone (PSf)/N,N-dimethylacetamide (DMAc)/diethylene glycol (DEG) solution. The α ranging between 0 and 100 % is a metric measuring how close the solution is to the cloud point. The increase of α endows instant phase separation, resulting in the substrate with increased surface porosity and sponge-like structure. Pore connectivity is improved following an increase of α below a threshold value of 50 %. Water permeability dramatically increases from α = 0 % to α = 50 % and declines at above 50 % for forming the closed cellular pores at α = 80 %. The FO water flux shows a similar trend which was found to be closely related to the substrate pore interconnectivity. The FO membrane was applied in the lithium concentration process using saturated MgCl2 as the draw, the experimental results fit well with the FO model. The results demonstrate a simple, low-cost generic method to prepare FO membranes for applications with very high salinity feed and draw.

Support-free interfacial polymerized polyamide membrane on a macroporous substrate to reduce internal concentration polarization and increase water flux in forward osmosis

Macroporous substrates have great potential in the development of high performance thin film composite forward osmosis (TFC FO) membranes. This paper reports on the preparation of TFC FO membrane via support-free interfacial polymerization (SFIP) technology on a macroporous substrate. SFIP technology can effectively break the bottleneck of conventional interfacial polymerization (IP) technology, which makes it difficult to form a complete polyamide (PA) film on the macroporous substrate. Briefly, the complete PA film is formed at the free water-organic phase interface and then attached to the macroporous substrate by vacuum filtration. The monomer concentration and filtration pressure were adjusted to form the optimal SFIP-PA film. Meanwhile, we chose a macroporous polyvinylidene fluoride (PVDF) microfiltration substrate and screened the pore size to reduce the structural parameters and then the internal concentration polarization, which caused the improvement of water flux. The performance of SFIP-PVDF membranes was investigated and discussed. Under the AL-FS mode with DI water and 1.0 M NaCl solution as the feed solution and draw solution, respectively, the SFIP-PVDF membrane, which used a macroporous PVDF substrate with a pore size of 0.45 μm exhibited a water flux (20 L/m2·h) and a reverse salt flux (2.5 g/m2·h). Besides, the membrane showed good stability in the 72 h test. The specific salt flux (Js/Jw) of SFIP-PVDF membranes was much lower than that of IP-PVDF membranes prepared via IP technology, which were incomplete and defective, suggesting that SFIP technology was superior to IP technology. This work effectively exploits the potential of macroporous substrates for the development of high performance TFC FO membranes and provides an insight into the high performance FO membrane design.

Predicting Water Flux in Forward Osmosis with Unknown Feed Solution Composition: An Empirical Approach Based on Thermodynamical Properties

This study investigated the predictability of forward osmosis (FO) performance with an unknown feed solution composition, which is important in industrial applications where process solutions are concentrated but their composition is unknown. A fit function of the unknown solution's osmotic pressure was created, correlating it with the recovery rate, limited by solubility. The osmotic concentration was derived and used in the subsequent simulation of the permeate flux in the considered FO membrane. For comparison, magnesium chloride and magnesium sulfate solutions were used since these show a particularly strong deviation from the ideal osmotic pressure according to Van't Hoff and are, thus, characterized by an osmotic coefficient unequal to 1. The simulation is based on the solution-diffusion model with consideration of external and internal concentration polarization phenomena. Here, a membrane module was subdivided into 25 segments of equal membrane area, and the module performance was solved by a numerical differential. Experiments in a laboratory scale for validation confirmed that the simulation gave satisfactory results. The recovery rate in the experimental run could be described for both solutions with a relative error of less than 5%, while the calculated water flux as a mathematical derivative of the recovery rate showed a bigger deviation.

Fabrication of highly permeable thin-film composite forward osmosis membrane using poly-l-lysine as an additive in polysulfone substrate

Forward osmosis (FO) has received considerable interest for water and energy-related applications in recent years. However, FO has not been commercialized yet because of a few reasons. The lack of a high-performance FO membrane is one of the important barriers. To overcome this issue, a novel high-performance thin-film composite (TFC) membrane was successfully fabricated via interfacial polymerization with poly-L-lysine incorporated polysulfone substrate (PSf). Compared to the pristine PSf substrate, the incorporation of lysine (ranging 1 – 15 wt.%) meaningfully alternates the substrates chemical structure, porosity, contact angle, and morphology leading to an enhancement of the lysine -TFC membranes performance. The results showed that the new substrates with higher porosity, more hydrophilic, and smaller in pore size after the introduction of L-lysine. The membrane achieved the highest FO water flux at 15% concentration of lysine and the maximum FO water flux was 35 L/m2.h (LMH) with a comparable specific salt flux (Js/Jw) of 0.002 g/L in the active layer facing the feed side (AL-FS) when 1M NaCl was applied as draw solution. The water flux was increased with increasing concentration of lysine. The addition of poly-L-Lysine in casting solution resulted in a more porous and hydrophilic support layer.

Rapid synthesis strategy of ultrathin UiO-66 separation membranes: Ultrasonic-assisted nucleation followed with microwave-assisted growth

The Metal-Organic Framework (MOF) materials are ideal molecular sieving membrane materials due to the regular pores with high-density and good designability, which have been widely studied in gas separation, desalination, and nanofiltration, etc. However, most preparation methods of MOF polycrystalline membranes are always time-consuming and the as-synthesized MOF membranes are thick. Here in this work, the ultrathin 210 nm-UiO-66 polycrystalline membranes are rapidly synthesized in 1 h, where sonication is utilized to generate massive tiny nucleation followed with rapid microwave-assisted membrane growth. The Na+ rejection of the UiO-66 membrane maintains at 99.6% for 700 h long-term experiment with 0.16 L/(m2 h bar) of water flux in forward osmosis, indicating the good quality and excellent stability of the as-synthesized membrane. This strategy is also expected to synthesize many other continuous defect-free MOF membranes with ultrathin thickness rapidly.

Introduction of poly(acrylic acid) sodium into traditional draw solution to enhance its driving capacity in forward osmosis process.

In this study, poly(acrylic acid) sodium (PAA-Na) salt was selected as representative polymer additive and the effect on forward osmosis (FO) performance of traditional draw solute NaCl was investigated. Results showed that PAA-Na increased water flux in both FO and PRO mode at 25 °C (up to 50%). Water flux and specific RSF firstly increased and then kept stable with the increasing concentration of PAA-Na additive. However, PAA-Na cannot enhance water permeation effectively at 35 and 45 °C. PAA-Na influenced FO performance by (1) increasing membrane hydrophilicity, which can increase water permeation, and was dominant at low temperature, and (2) causing pore-clogging, leading water flux decline, which was significant at high temperature. Furthermore, the influence of PAA-Na was compared with another polymer PAM and divalent salts MgCl2. The addition of PAM increased water flux slightly (lower than 25%), but increased RSF at the same time, due to the negative charge. Although MgCl2 decreased RSF and kept water flux fixed, its role was not obvious. In all, PAA-Na had advantages to improve FO performance.

Taking advantage of large water-unstable Zn4O(BDC)3 nanoparticles for fabricating the PMM-based TFC FO membrane with improved water flux in desalination process

Developing the forward osmosis (FO) membranes to enhance their efficiency is of great importance as this technology is an important option to overcome water scarcity. In the present study, the water-unstable Zn4O(BDC)3 (where BDC = 1,4-benzodicarboxylate) nanoparticles of different sizes were embedded into the polyethersulfone (PES) matrix to form the porous-matrix membranes (PMMs) as the support layers in the forward osmosis FO thin-film composite (TFC) membranes. The main idea of this approach is to suppress the negative effect of the dilutive internal concentration polarization (DICP) in the FO mode by increasing the mean pore size and porosity of the support layer of the TFC FO membranes, leading to an enhanced FO water flux. According to the results, the water flux (Jw) increased from 26 L/m2.h in the pristine membrane (TFC-C) to 34 L/m2.h in the TFC-MOF-2 membrane fabricated with the large size Zn4O(BDC)3 nanoparticles (108 nm particle size and 2 wt. % loadings). Also, this membrane was used for the Caspian seawater desalination, and the water flux of 28.10 L/m2h (18.72 for the TFC-C) and the water flux reduction of 6 % (18.48 % for the TFC-C) during the long-term experiment were obtained.

Synergistic effect of highly porous microstructured support and co-solvent assisted interfacial polymerization on the performance of thin-film composite FO membranes

Internal concentration polarization (ICP) in a dense support layer is one of the main reasons holding back forward osmosis (FO) process. In this regard, a highly porous microstructured support (HPμS) featuring a quasi-sponge-free sublayer pore structure can be considered a suitable alternative to develop high-performance FO membranes. However, it has not been tested for its effects on FO. This study demonstrates that a TFC membrane prepared using the HPμS works out for FO by inducing 3.35 times higher water flux without compromising a reverse salt flux (Js) compared to a control TFC membrane prepared without support adjustment. The performance improvement could be achieved by HPμS's almost no sponge-like region and lateral walls, which were desirable to minimize ICP. Furthermore, we verified that it is possible to leverage co-solvent assisted interfacial polymerization (CAIP) to further improve FO membrane performances by creating a more permeable active layer. The in-house TFC membrane optimized by the HPμS and CAIP displayed 5.3 times higher FO water flux than the control membrane, while keeping comparable Js. We expect that this research could contribute to kicking the FO membrane performance up a notch by providing a practical example of simultaneous optimization of both support and active layers.

FO–MD integrated process for nitrate removal from contaminated groundwater using seawater as draw solution to supply clean water for rural communities

Access to clean water has become a global concern in recent years, especially in rural communities due to the contamination of groundwater induced by intensive anthropogenic activities. The current study proposed a solution for this issue by the evaluation of the feasibility of forward osmosis (FO) coupled with membrane distillation (MD) to treat nitrate-contaminated groundwater using seawater as draw solution. The studied groundwater had high nitrate levels of 150 mg/L. The evaluation of different operating conditions indicated that working at lower FS concentration, higher DS concentration, higher DS temperature and under active layer draw solution (AL-DS) mode had positive effects on FO water flux. However, reverse solute flux and nitrate flux showed an increment with increasing FS concentration, DS concentration and DS temperature. Application of optimal operating conditions on real groundwater using seawater as DS, during 15 h of continuous operating time, led to obtain FO water flux of 6.25 LMH, MD permeate flux of 12.44 LMH, nitrate flux of 0.69 gMH, reverse solute flux of 20.24 gMH, FO rejection rate of 98.34% and MD salt rejection rate of 99.05%. Moreover, FO–MD process produced freshwater with almost free-nitrate content and very low conductivity of 78 µS/cm suitable for drinking and irrigation purposes. Thus, the integrated FO–MD process can be applied efficiently to remove nitrate from contaminated groundwater.

Improved thin-film-composite forward-osmosis membrane for coal mine water purification

During the emergency rescue, such as coal mining disasters, potable water was the primary factor to ensure the safety of people trapped underground, and it was easy to be obtained by the filtration of coal mine water. As a membrane separation technology, forward osmosis (FO) membranes were expected to be used in the emergency filtration of coal mine water with higher contents of SO42− and F−. In this paper, a thin film composite (TFC) FO membrane was prepared by phase conversion and interfacial bonding methods, and the influence of compound modification by TiO2, polyvinyl alcohol (PVA) and polydopamine (PDA) on the morphology and permeability of the TFC FO membrane was studied. The results show that the large size TiO2 (50 nm) was only physically deposited on the polysulfone (PSF) membrane, and PVA increased the binding strength of the PDA membrane to the polyamide (PA) membrane. As a result, 2 wt% TiO2 and 2 wt% PVA and PDA co-doping led to a low water contact angle of 27° and a high FO water flux performance of 12.9 LM−2H−1 using a 2 M NaCl draw solution. Furthermore, the composite membrane showed better hydrophilicity, and the rejection of SO42− and F− were 92.1% and 89.3%, respectively, indicating that TiO2 improved the internal channels of the TFC FO membrane and PVA and PDA increased the hydrophilicity of the PA layer. Therefore, the novel TFC FO membrane exhibited good rejection and reproducibility, and this study demonstrated that TFC FO membrane was a good candidate for the emergency filtration of coal mine water.

Gas responsive magnetic nanoparticle as novel draw agent for removal of Rhodamine B via forward osmosis: High water flux and easy regeneration

The effective draw agent is vital for developing the forward osmosis (FO) process in water reclamation applications. We have explored the feasibility of using gas-responsive magnetic nanoparticles (NPs) as a novel draw agent for the FO-based separation process. These NPs were fabricated by growing CO2-responsive poly[2-(dimethylamino)ethyl methacrylate] on magnetic Fe3O4 NPs surface (Fe3O4@PDMA). The successful growth of PDMA brushes on the Fe3O4 NPs was confirmed by FTIR, XRD, SEM, VSM, EDS, DLS, Zeta and TGA analysis. Then, the FO water flux, pH and CO2-responsibility, regeneration and dye-removal performance of Fe3O4@PDMA were thoroughly evaluated. The Fe3O4@PDMA NPs were exhibited considerable water flux in acidic conditions. Moreover, the CO2 purging time on water flux was studied. Experimental results revealed that the FO water flux increased with the increase in CO2-purging time. The water flux driven by the Fe3O4@PDMA NPs was found to be a strong function of the net polymer coverage on M NPs, that is, net available hydrophilic groups. The results showed that the water flux of Fe3O4@PDMA-12 h (high content) was much higher than that of Fe3O4@PDMA-4 h (low content). In addition, tunable protonation/deprotonation of PDMA brushes allows us to recycle the draw agent using an external magnetic field with minimum energy consumption. Furthermore, high water flux was achieved for Fe3O4@PDMA in colored wastewater treatment via the FO process.

Application of Waste Glycerol as a Draw Solution for Forward Osmosis.

Waste glycerol generated during biofuel production accounts for ~10% of total biodiesel volume. Increasing the use of renewable energy sources, including so-called biodiesel, will significantly increase the amount of waste glycerol for disposal. One possible route for waste glycerol reuse is to use it as a draw solution in forward osmosis (FO). Glycerol solutions are particularly suited as FO draw solutions due to their high osmotic pressures. In this work, the effects of waste glycerol composition on FO draw solution osmotic pressures, as well as the effects of membrane type and linear flow velocities on FO water and reverse flux, were investigated. Those results indicated the feasibility of using waste glycerol as a draw solution in FO, allowing the reuse of significant amounts of this by-product.

Optimization of Magnetic Nanoparticles Draw Solution for High Water Flux in Forward Osmosis

In this study, bare iron oxide nanoparticles were synthesized using a co-precipitation method and used as a draw solute in forward osmosis. The synthesis conditions of the nanoparticles were optimized using the Box-Behnken method to increase the water flux of the forward osmosis process. The studied parameters were volume of ammonia solution, reaction temperature, and reaction time. The optimum reaction conditions were obtained at reaction temperature of 30 °C, reaction time of 2.73 h and 25.3 mL of ammonia solution. The water flux from the prediction model was found to be 2.06 LMH which is close to the experimental value of 1.98 LMH. The prediction model had high correlation factors (R2 = 98.82%) and (R2adj = 96.69%). This study is expected to be the base for future studies aiming at developing magnetic nanoparticles draw solution using co-precipitation method.

High-Performance Thin-Film nanocomposite forward osmosis membranes modified with Poly(dopamine) coated UiO66-(COOH)2

• Surface functionalization of UiO-66 with polydopamine (UiO-PDA). • Thin film nanocomposite (TFN) forward osmosis (FO) membranes were fabricated by incorporating UiO-PDA. • UiO-PDA as a hydrophilic nanomaterial enhanced the separation performance of TFN-FO membranes. • The UiO-PDA modified TFN membrane exhibited better anti-fouling performance and Cu +2 ions rejection in comparison with bare TFC one. In this study, a new family of thin-film nanocomposite forward osmosis (TFN-FO) membranes was synthesized by embedding polydopamine (PDA) coated UiO-66-(COOH) 2 (UiO-PDA) nanofiller in polyamide (PA) rejection layer via interfacial polymerization (IP). The PDA coating assisted the UiO dispersion in MPD/water media, resulting in better chemical miscibility between the UiO-PDA and PA matrix. The impact of the UiO-PDA incorporation on the physicochemical properties (surface chemical composition, hydrophilicity, morphology, and roughness) of the TFN membranes are systematically examined via different characterization techniques. Besides, the effect of UiO-PDA concentration on the overall performances (FO water flux, reverse salt flux, antifouling tendency) of the obtained UiO-PDA modified TFN-FO membranes were investigated in a cross-flow FO system. Compared with the pristine thin film composite (TFC) membrane, the modified TFN membranes presented higher selectivity, water flux, and anti-fouling tendency. Finally, the TFN-UC.2 (modified with 0.03 wt% UiO-PDA) membrane exhibited greater Cu 2+ ions removal in FO mode (feed solution in contact with PA active layer) than the control TFC membrane, arising from their improved PA rejection layer characteristics.

Forward Osmosis Absorption Heat Pumps for Space Conditioning and Graywater Purification: Cycle Development and Working Fluids Selection

Abstract A thermodynamic model is developed for a forward osmosis (FO) absorption heat pump capable of purifying graywater and providing year-round space conditioning with low-temperature heat as the primary energy input. The model is applied to 16 potential absorbents, and six are selected for parametric studies on desorber temperature, absorber temperature, condenser temperature, and heat sink temperature to determine the effects on the energy ratio (defined as the ratio of total useful output to total power input) of the cycle and the required graywater flowrate. Experiments are conducted to test the water flux and reverse solute flux in FO for the most promising absorbents. Of the six selected absorbents, four to two salt-organic mixtures and two pure salts appear to have the most promising thermodynamic behavior, while an ionic liquid demonstrates the best FO behavior.

The effect of nanosheets on polymer hydrogels performance in Rhodamine B dye removal by forward osmosis process

This study provides a novel and straightforward method for preparing nanocomposite polymer hydrogels (NPHs) as high-performance forward osmosis (FO) draw agents. Pure polymer hydrogel was synthesized via in-situ free-radical copolymerization of acrylic acid (AA) and N-vinyl pyrrolidone (NVP) monomers. Precisely, NPHs were fabricated through the same procedures except for the use of different nanosheets (clay and graphene oxide, GO). The successful incorporation of clay and GO into the hydrogel matrix was confirmed by different analyses. Then, the effect of nanofiller type on the microstructure characteristics (surface porosity), swelling ratio, and FO-performance (FO water flux and water recovery) of the modified NPHs were systemically studied. Compared to the pure hydrogel, clay and the GO-modified NPHs (with 0.5 wt% nanofiller) presented higher FO water flux due to improved swelling ratio, osmotic pressure gradient, and hydrogel surface porosity. In addition, the NPHs were recovered and reused four times without any significant reduction in FO water flux. Finally, the best performing clay and GO-modified NPHs were used as proper draw agents to treat the water-soluble Rhodamine B dye from an aqueous solution (200 ppm). Therefore, this study provides a simple method for preparing highly porous and hydrophilic NPHs, which can probably have potential applications in the FO process.

News on alginate recovery by forward osmosis: Reverse solute diffusion is useful

The water content in the recycled alginate solutions from aerobic granular sludge was nearly 100%. Forward osmosis (FO) has become an innovative dewatering technology. In this study, the FO concentration of sodium alginate (SA) was investigated using calcium chloride as a draw solute. The reverse solute flux (RSF) of calcium ions in FO had a beneficial effect, contrary to the findings of previous literature. The properties of the concentrated substances formed on the FO membrane on the feed side were analyzed by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy, verifying that calcium alginate (Ca-Alg), which can be used as a recycled material, was formed on the FO membrane on the feed side owing to the interaction between SA and permeable calcium ions. Water flux increased significantly with the increase in calcium chloride concentration, while the concentration of SA had little influence on the water flux in FO. Based on this discovery, we propose a novel method for the concentration and recovery of alginate, in which the RSF of calcium ions is utilized for recovering Ca-Alg by FO, with calcium chloride as a draw solute.

A novel concept of Vertical Up-Flow Forward Osmosis reactor: Design, performance and evaluation

Performance of the forward osmosis (FO) process is limited due to the decline in water flux and increase in reverse salt flux. In this study, a novel Vertical Up-Flow Forward Osmosis (VUF-FO) reactor was designed and evaluated for eight different contacting patterns of feed and draw agent (DA). The best contacting pattern was compared with the basic H-shape reactor. Pulsating inlets were used for the recirculation of the feed and DA which helped in improving the performance by reducing the concentration polarization on membrane. Water flux in FO (active layer facing feed side) and PRO (active layer facing draw side) mode was 12.75 and 16.28 L/m2hr (LMH) respectively for the contacting pattern R3 and R5 after 8 h of the process. While the water flux in the H-shape reactor was 9.12 and 12.54 LMH for FO and PRO mode respectively. Diffusional behavior of water flux and reverse salt flux were also evaluated for both the FO reactors. Water flux in the H-shape reactor was declined to more than 60% from its initial value in both the modes (i.e. FO and PRO) due to the concentration polarization on membrane. Only 10% decline in water flux was observed for the VUF-FO reactor. This showed a better consistency of water flux in the VUF-FO reactor. The reverse salt flux in the VUF-FO reactor was less than 85% compared to the H-shape reactor. Therefore, a novel designed reactor improved the overall performance of FO in terms of water flux and reverse salt flux.