Draw Solution Recovery Research Articles

Investigating novel thin-film nanocomposite membranes for sustainable water recovery using fertilizer-driven forward osmosis – Experimental and machine learning approaches

Water recovery from municipal wastewater can augment freshwater resources to meet increasing demand. An osmotic-driven membrane separation process- forward osmosis (FO) is currently being explored as a sustainable technology. This work proposes to address the challenges associated with FO namely (i) robust membrane and (ii) draw solute (DS) recovery. Robust thin-film nanocomposite membranes incorporating a) nickel ferrite or b) nitrogen-enriched nanoporous polytriazine (NENP-1) covalent organic framework were fabricated with enhanced hydrophilicity, surface roughness and anti-fouling properties. The optimum membranes M2 and C2 displayed a pure water flux of 4.86 ± 0.11 and 5.4 ± 0.2 L/m2h respectively and a specific reverse solute flux (SRSF) <<1 when using 1 M NaCl solution as the DS (feed solution – DI water). Fertilizer-driven FO (FDFO) was proposed as the diluted DS need not be recovered but could be used directly for irrigation. The pure water flux for both M2 and C2 membranes were in the following order for the fertilizers used as DS (1 M) - (NH4)2SO4 + (NH₄)₂HPO₄ > (NH4)2SO4 > (NH₄)₂HPO₄ which indicates that the mixed ions in the DS enhanced the water permeance. In all cases, the SRSF was < 1 g/L indicating the feasibility of the process. The membranes exhibited a TOC removal of > 90 % from synthetic municipal wastewater containing persistent organic pollutants and personal & pharmaceutical care products and the membranes could be regenerated after washing with a 10 mM solution of SDS for 5 cycles of operation. Further, ANN was used to develop a predictive model for water flux in FO membranes and the optimized architecture of 7–5–50–40–1 displayed a remarkable overall R2 value of 0.98 (MSE= 0.027). The FDFO process using the fabricated thin-film nanocomposite membranes holds enormous potential to be investigated in larger-scale studies.

Selection of optimal draw solution recovery technology for forward osmosis desalination system using analytical hierarchy process

Water scarcity poses a significant threat to global food and water security, prompting a need for practical solutions. With 97% of Earth’s water situated in oceans, desalination emerges as a viable option. Among desalination technologies, forward osmosis (FO) using membrane-based technology stands out for its potential to reduce costs and energy requirements. The focus on energy consumption in FO has prompted an exploration of optimal technology selection through the Analytical Hierarchy Process (AHP), a multi-criteria decision-making method. Value judgments were collected through a questionnaire in consultation with two experts. Environmental aspects emerged as the most critical factor, weighted at 0.3963. The AHP analysis revealed nanofiltration (NF) as the optimal system, attaining a total weight of 0.2612. The NF scored highest in terms of environmental impact (C3), operating and maintenance costs (S6), and energy requirements (S4). Conversely, membrane distillation ranked as the least preferred alternative, with a total score of 0.1335, mainly due to lower maturity of technology (S3), higher capital costs (S5), and negative environmental impact (C3). Sensitivity analysis was conducted to investigate how changing weights for sub-criteria might affect the preferred technology. Notably, Reverse Osmosis became the most favored technology when efficiency (S1) and S3 weights were set at 0.3 and 0.2, respectively. Conversely, thermal separation gained preference when the weights for resistance to scaling and fouling (S2) and S5 were set at 0.3. Changes in S4, S6, and C3 have showed the most minor sensitivity.

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.

Sodium functionalised carbon nanofibers draw solution for a solar-thermal forward osmosis water desalination system

Desalination offers the potential to bridge the demand-supply gap in the increasing global freshwater scarcity, with the forward osmosis (FO) technique appearing as an attractive solution amongst the various desalination technologies. However, the significant energy demand encountered during the draw-solute recovery process in FO desalination is considered the major anathema amongst other contending factors for which the allure of FO as a desalination technology becomes questioned. Consequently, a potentially innovative draw solution (DS) regeneration strategy, enabling the circumvention of the energy requirements associated with the recovery stage in FO desalination, is evaluated. The direct solar thermal FO (DSTFO) desalination concept is predicated on engineering and applying solar absorptive DS to directly leverage solar energy for solute recovery without recourse to electric power. In advancing the DSTFO concept, this study fabricated and evaluated a novel and highly osmotic sodium functionalised carbon nanofibres (Na/CNF) DS having a high osmotic pressure (93.9 bar), a low reverse solute flux (RSF) of 0.24 gMH, and a photothermal conversion efficiency of 63.49%, resulting in an evaporation rate of 1.85 kg/m2/hr under 2 suns of solar radiation. The DSTFO strategy offers a low-cost solution for enhancing water recovery and decreasing energy use in FO desalination systems.

Continuous purification of drugs by ionic liquid-drawn organic solvent forward osmosis and solute recovery

Classical purification of pharmaceuticals is energy-intensive and employs toxic solvents that are discarded, calling for more sustainable methods. Here, we purified tetracycline by organic solvent forward osmosis using ionic liquids. Results show the osmotic enrichment of feed solutions containing different concentrations of tetracycline in methanol. The solvent flux during the filtration process is mainly influenced by solvent properties, such as molecular size, viscosity, polarity, and the solvent–membrane interaction. We evaporated the diluted draw solution to recover the draw solute for reuse. Overall ionic liquids appear as suitable draw solutes for organic solvent forward osmosis for pharmaceutical compound enrichment with draw solute recovery and reuse.

Microwave Synthesis of Poly(Acrylic) Acid-Coated Magnetic Nanoparticles as Draw Solutes in Forward Osmosis.

Polyacrylic acid (PAA)-coated magnetic nanoparticles (MNP@PAA) were synthesized and evaluated as draw solutes in the forward osmosis (FO) process. MNP@PAA were synthesized by microwave irradiation and chemical co-precipitation from aqueous solutions of Fe2+ and Fe3+ salts. The results showed that the synthesized MNPs have spherical shapes of maghemite Fe2O3 and superparamagnetic properties, which allow draw solution (DS) recovery using an external magnetic field. Synthesized MNP, coated with PAA, yielded an osmotic pressure of ~12.8 bar at a 0.7% concentration, resulting in an initial water flux of 8.1 LMH. The MNP@PAA particles were captured by an external magnetic field, rinsed in ethanol, and re-concentrated as DS in repetitive FO experiments with deionized water as a feed solution (FS). The osmotic pressure of the re-concentrated DS was 4.1 bar at a 0.35% concentration, resulting in an initial water flux of 2.1 LMH. Taken together, the results show the feasibility of using MNP@PAA particles as draw solutes.

Concentration of skim milk by forward osmosis using delactosed permeate as an innovative draw solution

Forward osmosis (FO) is proposed as a sustainable alternative to evaporation and reverse osmosis, but its commercial application is limited by energy-intensive draw solution recovery and solute permeation through the membrane. To mitigate this, the dairy by-product delactosed permeate has potential as a draw solution for concentration of dairy products, where permeation of solutes and draw solution recovery are not a concern. In this study, skim milk was concentrated from 9 to 18% dry matter by FO using delactosed permeate as the draw solution. The influence of temperature on filtration performance was assessed whereby average fluxes of 3.6 and 4.8 kg h−1 m−2 were obtained at 10 and 30 °C, respectively. Energy savings of ∼57% per kg of water removed compared with reverse osmosis were observed. This, together with the absence of undesirable solute permeation during FO, highlights the potential of delactosed permeate as a draw solution for concentration of dairy streams.

Water and nutrient recovery from stored urine by forward osmosis with an ammonium bicarbonate draw solution

Forward osmosis with an ammonium bicarbonate draw solution was investigated as a low energy non-sewered sanitation solution, to recover nutrients and water from source separated urine. Stored urine collected from Urine Diversion Dry Toilets in the eThekwini Municipality (Durban), South Africa was used as the feed solution. Water recoveries of up to 45.9% with water fluxes up to 6.0 L m−2 h−1 were achieved using undiluted stored urine over an 8-h operating period with a 2.5 M draw solution. Rejections of up to 95% for phosphates, 85% for nitrogen and chlorides, and 75% for potassium and sodium were achieved. Low fouling of the membrane was observed after multiple runs and cleaning the membrane by circulation of deionized water or by osmotic backwash was sufficient to recover &amp;gt;95% of the original water flux. Little irreversible fouling was detected, assumed to be caused by carbonate calcium scaling from SEM-EDX analysis. This study suggests that forward osmosis with an ammonium bicarbonate solution could be integrated as a closed loop nutrient recycling technology for source separated urine with the prospect of clean water and draw solution recovery that could use waste heat from, for example, fecal sludge combustion.

A novel highly osmotic K/Fe3O4/CNF magnetic draw solution for salty water desalination

Forward osmosis (FO) is increasingly being studied as an alternative desalination technique to the other conventional desalination technologies, owing primarily to its low energy potential. However, the co-opted energy limitations in the draw solution (DS) regeneration stage in FO desalination processes and the lack of effective DS have hampered FO's implementation for potable water application on an industrial scale. In this work, we explored the Donnan principle to engineer a DS material having the duality of magnetic and solar-thermal separability functionalities from a sustainability viewpoint whilst exploiting a careful selection of material properties. A novel potassium functionalised iron oxide doped carbon nanofibres (K/Fe3O4/CNF) magnetic nanoparticles (MNPs) was successfully synthesised for FO desalination applications, utilising an eco-friendly strategy that improves hydrophilicity of DS without polymers. The novel DS obtained a significant osmotic pressure (86.1 bar), whilst it FO performance showed a small reverse salt flux (RSF) and specific reverse salt flux (SRSF) values of 0.10 gMH and 0.004 g/L, respectively. These values compare to at least <10 % of most RSF and SRSF values reported in the literature. The facile DS synthesis strategy adopted herein will potentially open a new route to preparing other DS nanomaterials with unique multi functionalities and enhanced hydrophilicity devoid of polymers. Whilst magnetic DS re-concentration may be achievable, additional research is required to appraise this methodology's overall energy implications and economic advantages over existing DS recovery methods.

Engineering pressure retarded osmosis membrane bioreactor (PRO-MBR) for simultaneous water and energy recovery from municipal wastewater

Osmotic membrane bioreactors (OMBR) have gained increasing interest in wastewater treatment and reclamation due to their high product water quality and fouling resistance. However, high energy consumption (mostly by draw solution recovery) restricted the wider application of OMBR. Herein, we propose a novel pressure retarded osmosis membrane bioreactor (PRO-MBR) for improving the economic feasibility. In comparison with conventional FO-MBR, PRO-MBR exhibited similar excellent contaminants removal performance and comparable water flux. More importantly, a considerable amount of energy can be recovered by PRO-MBR (4.1 kWh/100 m2·d), as a result of which, 10.02% of the specific energy consumption (SEC) for water recovery was reduced as compared with FO-MBR (from 1.42 kWh/m3 to 1.28 kWh/m3). Membrane orientation largely determined the performance of PRO-MBR, higher power density was achieved in AL-DS orientation (peak value of 3.4 W/m2) than that in AL-FS orientation (peak value of 1.4 W/m2). However, PRO-MBR suffered more severe and complex membrane fouling when operated in AL-DS orientation, because the porous support layer was facing sludge mixed liquor. Further investigation revealed fouling was mostly reversible for PRO-MBR, it exhibited similar flux recoverability (92.4%) to that in FO-MBR (95.1%) after osmotic backwash. Nevertheless, flux decline due to membrane fouling is still a restricting factor to power generation of PRO-MBR, its power density was decreased by 38.2% in the first 60 min due to the formation of fouling. Overall, in perspective of technoeconomic feasibility, the PRO-MBR demonstrates better potential than FO-MBR in wastewater treatment and reclamation and deserves more research attention in the future.

EDTA-Na2 as a recoverable draw solute for water extraction in forward osmosis

Regeneration and reuse of draw solute (DS) is a key challenge in the application of forward osmosis (FO) technologies. Herein, EDTA-Na2 was studied as a recoverable DS for water extraction by taking advantages of its pH-responsive property. The FO system using EDTA DS achieved a higher water flux of 2.22 ± 0.06 L m−2 h−1 and a significantly lower reverse salt flux (RSF) of 0.06 ± 0.01 g m−2 h−1, compared to that with NaCl DS having either the same DS concentration or the same Na+ concentration. The suitable pH range for the application of EDTA DS was between 4.0 and 10.5. A simple recovery method via combined pH adjustment and microfiltration was employed to recover EDTA DS and could achieve the recovery efficiency (at pH 2) of 96.26 ± 0.48%, 97.13 ± 1.03% and 98.56 ± 1.40% by using H2SO4, H3PO4 and HCl, respectively. The lowest acid cost for DS recovery was estimated from 0.0012 ± 0.0001 to 0.0162 ± 0.0003 $ g−1 by using H2SO4. The recovered EDTA DS could be reused in the subsequent FO operation and the overall recovery efficiency was 94.4% for four reuse cycles. These results have demonstrated the feasible of EDTA-Na2 DS and a potentially cost-effective recovery approach, and encouraged further exploration of using EDTA-based compounds as a draw solute for FO applications.

Evaluation of cellulose triacetate hollow fiber membrane for volume reduction of real industrial effluents through an osmotic concentration process: A pilot-scale study

The current article tackles the challenge of reducing wastewater volumes generated from the gas industry. A forward osmosis (FO) pilot unit, deployed as osmotic concentration (OC) process without the draw solution (DS) recovery step, was applied as an option for volume reduction of real industrial effluents. A commercial hollow fiber (HF) FO membrane fabricated from Cellulose Triacetate (CTA) was firstly tested with synthetic feed solution (FS) to investigate the separation properties of the membrane and to identify the optimum operating conditions of the pilot unit. The pilot plant was then challenged with real industrial wastewater for an extended period of operation, primarily to assess membrane-fouling propensities and other performance parameters. Results revealed that according to the operating conditions, the CTA membrane can achieve feed recoveries between 60%–90%, at water fluxes between 2.24-1.65 L.m −2 h −1 (LMH)). The operation at 75% feed recovery was identified as the optimum condition since it showed the lowest specific solute flux (20.93 mmol L −1 ) at a water flux of 1.94 LMH. Outcomes of pilot testing with the real wastewater demonstrated operational stability for over 50 h of continuous operation. The pilot system recovered 75% of the wastewater feed at a stable flux trend with minimal flux decline. Water flux of 1.76 LMH was recorded along with reverse solute flux of 292 mmol h −1 . The water flux was observed to decline slightly by only 5.6%, which was attributed to inorganic scaling on the membrane surface where cleaning with citric acid solution demonstrated efficacy in restoring the initial flux. • The technical viability of osmotic concentration (OC) technology at a pilot scale was appraised. • The performance of a commercial CTA HF membrane was evaluated. • The role of operating conditions in the performance of the pilot unit was examined. • OC pilot unit successfully recovered 75% of real wastewater generated from the gas industry. • Stable flux was observed during 50 h of continuous operation with minimal membrane fouling.

Electrolysis-assisted recovery of reverse-fluxed solutes in forward osmosis

Reverse solute flux (RSF) is a key issue for operating forward osmosis (FO) systems and can cause the loss of draw solute (DS) and salt accumulation in the feed. Herein, an electrolysis-assisted FO (e-FO) system was developed for simultaneous RSF reduction and recovery of the reverse-fluxed DS. Applying a voltage of 1.5 V led to RSF of 3.34 ± 0.01 mmol m−2 h−1 (0.47 g m−2 h−1) in the e-FO system, 67.5 ± 0.5% lower than that of the control system; in addition, the e-FO system recovered ~0.32 g L−1 of the reverse-fluxed DS and this could not be realized in the control. When the e-FO system was examined with three types of the mimicked fertilizer, RSF reduction and DS recovery were largely affected by the individual components of a fertilizer DS. The energy consumption of the e-FO system was reduced by ~90%, from 0.38 ± 0.01 to 0.04 ± 0.01 kWh m−3 when the recirculation rate decreased from 60 to 15 mL min−1. Those results have demonstrated the technical feasibility of an e-FO system that is capable of reducing RSF and recovering the lost DS and will encourage further investigation by addressing several identified challenges.

Enhanced solar-driven evaporation process via f-MWCNTs/PVDF photothermal membrane for forward osmosis draw solution recovery

Product water recovery and draw solution (DS) reuse is the most energy-intensive stage in forward osmosis (FO) technology. Sucrose solution is the most suitable DS for FO application in food and beverages. However, sucrose DS recovery by conventional pressure-driven or thermal-driven concentration techniques consumes high energy. Herein, we developed a spontaneous and sustainable solar-driven evaporation process based on a photothermal membrane for the concentration and recovery of sucrose solution. The photothermal membrane composed of multi-walled carbon nanotubes (f-MWCNTs) phtotothermal layer on a hydrophilic polyvinylidene fluoride (PVDF) substrate. The f-MWCNTs photothermal layer with rough surface and interconnected network structures not only improves the light harvesting and light-to-heat conversion performance, but also facilitates the transport of water molecules. The hydrophilic PVDF substrate can promote the rapid transport of water for adequate water supply to photothermal layer. As a result, the optimized f-MWCNTs/PVDF photothermal membrane exhibits an excellent light absorption of 95%, and a high surface temperature of 74 °C at 1 kW m−2. Besides, it realizes an evaporation rate of 1.17 kg m−2 h−1 for 5% (w/v) of sucrose solution, which is about 5 times higher than that of the natural evaporation. The designed photothermal evaporation process is capable of concentrating sucrose solution efficiently from 5% to 75% (w/v), which has great potential in FO process and juice concentration.

Forward osmosis using highly water dispersible sodium alginate sulfate coated-Fe3O4 nanoparticles as innovative draw solution for water desalination

The remarkable advancement of forward osmosis (FO) as a promising technology for water treatment encounter difficulties due to the synthesis and recovery of a suitable draw solution (DS). The easy recyclability of the draw solution and energy consumption are the critical issues in FO processes. In this work, we have introduced the magnetic core-hydrophilic shell nanoparticles as an efficient draw solute for FO processes. The surface of nanoparticles was modified with sodium alginate sulfate (SAS) as a biocompatible, low toxic and relatively low-cost hydrophilic material. In this regard, the dispersibility and stability of Fe3O4 nanoparticles in aqueous solution was enhanced. The average water flux of 0.06 g mL–1 Fe3O4@SiO2-SAS was determined as 12.8 and 8.5 L m–2 h–1 with a reverse solute flux of 1.48 and 0.23 g m–2 h–1 in PRO and FO modes, respectively. Concentrations of 0.05, 0.1 and 0.2 M NaCl have been used as feed solution to study the performance of the DS for desalination process. Moreover, the optimum DS was successfully used for treatment of a real wastewater. Eventually, the synthesized draw solution was recovered by a magnetic field and its reusability was tested. High stability and simple regeneration of DS decreases the cost of water production.

Industrial wastewater volume reduction through osmotic concentration: Membrane module selection and process modeling

Osmotic concentration (OC), a form of forward osmosis (FO) but without draw solution recovery, can be applied for reducing wastewater disposal volumes in the oil & gas industry. Within this industry, wastewater is often disposed of by injection through disposal wells into deep underground reservoirs. By reducing wastewater disposal volumes, the sustainability of the disposal reservoir is improved. In this application of OC, seawater or brine from a desalination plant serves as the draw solution and the diluted seawater is discharged to the sea. This study compared 3 commercial hollow-fiber FO membranes (CTA, TFC, aquaporin proteins) for reducing the volume of low salinity wastewater generated during liquified natural gas (LNG) production. Additionally, a model was developed to predict the performance of commercial full-scale membranes by identifying optimum operating conditions, taking into consideration the trade-off between feed concentration factor and water flux. Bench-scale tests were conducted using synthetic and actual wastewater from an LNG facility to evaluate OC technology performance and validate model predictions.Based on model results with a feed mimicking the salinity of actual wastewater, a 4x concentration factor produced a reasonable compromise between feed recovery and draw solution dilution and was considered the optimum for future tests. At higher concentration factors, the increased dilution of the draw solution negatively impacted flux. In bench tests with real wastewater, the TFC chemistry had a ≈5x higher water flux (9.7 vs. 1.9 L/m2-h) and a ≈3x lower specific reverse solute flux (192 vs. 551 mg/L) compared to the CTA chemistry. However, both membranes showed less than 5% fouling and a specific forward organic solute flux of less than 0.5 mg/L of total organic carbon (TOC). Pilot testing for >50 h showed stable performance, comparable to bench scale data and model predictions.

Pilot-scale investigation of flowrate and temperature influence on the performance of hollow fiber forward osmosis membrane in osmotic concentration process

Forward osmosis (FO) relying on the osmotic pressure difference across semi-permeable membrane draws permeate by the effect of saline draw solution (DS) turning diluted and leaving the feed solution (FS) concentrated. However, the energy intensive step of DS recovery makes FO a challenging process. The energy benefit of FO emerges when recovery step is obviated and FO is applied as an osmotic concentration (OC) process. OC implementations for volume reduction are still at bench-scale and the investigation at larger scale is among the breakthroughs. In this paper, the performance of hollow fiber (HF) membrane in pilot-scale OC process for reducing volume of feed was investigated. The impact of operating conditions such as flowrates and temperature was evaluated. FS and DS flowrates of 1.35 and 0.35 L.min-1 respectively are optimum conditions with 75% feed recovery and 1.90 LMH water flux. Reverse solute flux increased at higher flowrates. Results indicated the role of high DS flowrate and temperature in improving the performance. DS flowrate of 0.35 L.min-1 at constant FS flow of 1.10 L.min-1 and 27 °C was most suitable for achieving 84.5% feed recovery and 1.82 LMH water flux. Above all, the long-term performance of OC pilot-plant was demonstrated through 48 h of continuous operation where stable flux trend at an average water flux of 1.66 LMH was successfully achieved. Lastly, the permeability coefficients of HF membrane were enhanced at higher temperature.

The Water Flux Dynamic in a Hybrid Forward Osmosis-Membrane Distillation for Produced Water Treatment.

Standalone membrane distillation (MD) and forward osmosis (FO) have been considered as promising technologies for produced water treatment. However, standalone MD is still vulnerable to membrane-wetting and scaling problems, while the standalone FO is energy-intensive, since it requires the recovery of the draw solution (DS). Thus, the idea of coupling FO and MD is proposed as a promising combination in which the MD facilitate DS recovery for FO—and FO acts as pretreatment to enhance fouling and wetting-resistance of the MD. This study was therefore conducted to investigate the effect of DS temperature on the dynamic of water flux of a hybrid FO–MD. First, the effect of the DS temperature on the standalone FO and MD was evaluated. Later, the flux dynamics of both units were evaluated when the FO and DS recovery (via MD) was run simultaneously. Results show that an increase in the temperature difference (from 20 to 60 °C) resulted in an increase of the FO and MD fluxes from 11.17 ± 3.85 to 30.17 ± 5.51 L m−2 h−1, and from 0.5 ± 0.75 to 16.08 L m−2 h−1, respectively. For the hybrid FO–MD, either MD or FO could act as the limiting process that dictates the equilibrium flux. Both the concentration and the temperature of DS affected the flux dynamic. When the FO flux was higher than MD flux, DS was diluted, and its temperature decreased; both then lowered the FO flux until reaching an equilibrium (equal FO and MD flux). When FO flux was lower than MD flux, the DS was concentrated which increased the FO flux until reaching the equilibrium. The overall results suggest the importance of temperature and concentration of solutes in the DS in affecting the water flux dynamic hybrid process.

Forward osmosis for industrial effluents treatment – sustainability considerations

Access to clean water resources has become a global challenge in recent times, especially in developing countries, where huge amounts of highly polluted industrial and municipal effluents are produced and discharged into the receiving environments. Applications of membrane technologies to deal with effluents from various origins have recently received a great deal of attention due to their inherent advantages compared to other physico-chemical methods developed so far. Forward osmosis (FO) is among one of the efficient membrane-based processes adopted by wastewater treatment facilities, with various configurations currently being transferred from laboratory and pilot-scales to large-scale applications. Still, FO technologies are plagued with drawbacks such as fouling, internal concentration polarization (ICP), reverse solute flux and draw solution recovery, which invariably increases the cost of operation and restricts the feasibility for large-scale and long-term use because economic considerations are the most important sustainability criteria when selecting a wastewater treatment technique among the various alternatives. Several modifications have been introduced in recent years to overcome the existing limitations, such as incorporation of engineered nanomaterials onto the membrane surface to mitigate membrane fouling and to enhance their life-time, thereby minimizing the cleaning and (when necessary) replacement costs. Several FO based pre-treatment technologies have also been introduced for complex effluents treatment to minimize the operational costs arising from cleaning and replacement activities. Therefore, assessing the performance of such technologies according to sustainability indicators is the key to ensure long-term benefits from the application of FO technologies for the treatment of highly polluted effluents. In this review, treatment and water reclamation from industrial effluents using FO process and the current states of the standalone and hybrid technologies considering sustainability criteria are discussed. Scaling-up opportunities for the existing lab-scale modules have been evaluated and environmental footprint of the under-developed technologies are discussed. This review will therefore aid in selecting the most suitable configurations of FO technologies (standalone/hybrid) to deal with the highly polluted effluents for real world applications and to direct future studies in this emerging area. Perspectives and recommendations for future studies are also included.

Recovery of iodide as triiodide from thin-film transistor liquid crystal display wastewater by forward osmosis

Triiodide, a larger charged molecule compared to iodide, is thermodynamically favored with the presence of both iodide and iodine, and is easier to be retained by membrane processes. For the first time, iodide was recovered in the form of triiodide by forward osmosis (FO) for thin-film transistor liquid crystal display industries by preoxidation of iodide to triiodide. Partial oxidation by NaOCl was used to convert the iodide to iodine and then to form triiodide. Ethylenediaminetetraacetic acid disodium salt (EDTA-2Na), a commonly used chelating agent in the industry, was used as the draw solute because of its low reverse salt flux. The results revealed that the ideal efficiency of iodide recovery was at pH 3 with a preoxidation (adding 0.0150 M NaClO) for the 0.048 M iodide wastewater with a recovery of 98.5%. Additionally, the Pourbaix diagram and starch indicator were used to verify the formation of triiodide. Membrane distillation was demonstrated to recover the EDTA-2Na draw solute, and more than 99% of recoveries for the draw solutes with initial water flux of 12.0 L/m2 h were achieved, indicating that simultaneous recovery of the EDTA-2Na draw solute and water is feasible.