Feed Solution Concentration Research Articles

Parametric analysis of reverse electrodialysis process for improved power generation: Influence of spacer thickness, feed solution flow rate, membrane, and concentration

Reverse electrodialysis (RED) technology produces electrical energy from a salinity gradient by transporting ions through ion-exchange membranes (IEM). Although research into this technology has recently seen considerable growth, there is still interest in improving its efficiency. As a result, a mathematical model to study the RED process was developed using Aspen Custom Modeler software, focusing on three membranes (Fumasep (FAD/FKD), Fujifilm Type 10, and Selemion (AMV/CMV)). A parametric analysis was conducted, considering spacer thickness, salinity gradient, and feed-solution flow rates. Evaluation of internal resistance, gross power density, and net power density was also performed. Results showed that using a thicker spacer (270 μm) in the high compartment and a thinner spacer (150 μm) with a high Reynolds number in the low compartment led to higher net power densities of 2.17 W·mcp−2 and 6.74 W·mcp−2 for Fumasep (FAD/FKD) membrane with (brackish/seawater) and (brackish/brine), respectively. Among the membranes tested, Fumasep (FAD/FKD) and Fujifilm Type 10 had similar results, with the former slightly exceeding the latter. However, the Selemion membrane (AMV/CMV) performed poorly in all tests.

Investigating the Effect of KOH Feed Concentration on a Stainless-Steel Anode Using a 3-Electrode Anion Exchange Water Electrolyser Cell Set-up

Anion-exchange membrane water electrolysers (AEM-WE) have the potential to lower the capital cost of hydrogen production compared to proton-exchange membranes water electrolysers (PEM-WE). The alkaline conditions of AEM-WE result in: (i) a kinetically more favourable oxygen evolution reaction (OER), (ii) the ability to use platinum group metal (PGM)-free metal catalysts, and (iii) reduced cell component costs because of the less corrosive operating conditions. However, AEM-WE is held back from commercialisation by limited current density and durability.1 Compared to conventional alkaline water electrolysis, AEM-WEs have the advantage of lower ohmic resistance thanks to a solid polymer electrolyte which provides intrinsic ionic conductivity instead of relying on 6 M KOH and a porous separator. Most studies show, however, that a dilute KOH feed (< 1 M), rather than pure water, is critical to reaching a high current density in AEM-WE. Varying the concentration of KOH in the feed solution impacts catalyst activity and membrane resistance thereby making performance measurements in AEM-WE more complex. Moreover, the overpotential for the alkaline hydrogen evolution reaction (HER) is significant due to its sluggish kinetics. This means full-cell measurements are insufficient for understanding the behaviour of OER and HER catalysts in AEM-WE. It is therefore crucial to make half-cell measurements in AEM-WEs to decouple the effect of the anode and cathode electrocatalysts from the overall cell performance.In this context, our group recently demonstrated a 3-electrode, 5 cm2 membrane electrode assembly electrolyser cell2 that uses a reference electrode to decouple the anode and cathode contributions to the overall water splitting reaction. The technique was demonstrated for AEM-WEs and is soon to be published by Malone et al. (Figure 1A)3. In this study, we aimed to investigate the effect of KOH concentration in the feed solution on OER by using this 3-electrode cell setup. We used a stainless steel (SS)-felt at the anode as both catalyst and porous transport layer (PTL) in different concentrations of KOH feed while maintaining Pt/C as the cathode catalyst. We also repeated the tests with various anode catalyst layers (IrOx, NiFeOx) in combination with the SS PTL. For each test, full and half-cell polarisation curves and impedance spectroscopy were recorded before and after a sixteen-hour durability test at 1 A cm-2 at 40 °C. The results revealed the catalytic significance of the SS-felt in 1 M KOH as recently shown by Chen et al.4 Additionally, we demonstrated how the SS masks the performance of an IrOx catalyst layer in 1 M KOH. Reducing the KOH concentration to 0.18 M resulted in ≈ 7 % increase in the overall cell voltage at 1 A cm-2 (from 1.88 V to 2.00 V at 40 °C in Figure 1B). Aside from the ≈ 35 % increase in membrane resistance (e.g. 180 to 240 mΩ cm2 at 0.9 A cm-2) in 0.18 M KOH, the higher overpotential arose from the anode (Figure 1C), which could be attributed to the higher OER overpotential of SS-felt in a lower pH solution. Meanwhile, there was no appreciable change in cathode overpotential when the KOH concentration was reduced. These findings demonstrate the importance of 3-electrode cell measurements for understanding the impact of each component in an AEM-WE cell. Furthermore, the results reveal that both the choice of PTL material as well as the concentration of feed solution should be considered when testing different catalysts in AEM-WE.

Novel ternary nanocomposite (TiO2@Fe3O4-chitosan) system for nitrate removal from water: an adsorption cum photocatalytic approach.

Nitrate pollution of water emerging from various anthropogenic activities has become a major environmental concern because of its deleterious effects on natural water resources. The present work deals with the synthesis of the ternary nanocomposite based on chitosan, iron oxide (Fe3O4), and titanium dioxide (TiO2) and its application for the removal of nitrates from model-contaminated water. Fe3O4 derived through a coprecipitation method was incorporated into the chitosan matrix which was fabricated in the form of beads. The wet gel beads were then successfully coated with sol-gel-derived silver-doped titanium dioxide sol followed by drying under suitable conditions to get the functional nanocomposite beads. The synthesized functional materials were further characterized for their structural, morphological, and textural features using X-ray diffraction analysis, physical property measurement (PPMS), Fourier transform infrared (FTIR) analysis, UV visible spectroscopy analysis (UV-vis), BET surface area analysis (BET), field emission scanning electron microscopic (FESEM), and transmission electron microscopy (TEM) analysis. The ternary nanocomposites were further used for the removal of nitrates via adsorption cum photocatalytic reduction technique from the model contaminated water when subjected to an adsorption study under dark conditions and photocatalytic study under UV/visible/sunlight for a definite time. Fe3O4 in the nanocomposite provides enhanced adsorption features whereas the functional coating of titanium dioxide aids in the removal of nitrates through the photocatalytic reduction technique. The functional beads containing 3% Fe3O4 in the wet gel form (CTA-F3) have excellent nitrate removal efficiency of ~ 97% via adsorption cum solar photocatalysis towards the removal of nitrate ions from 50ppm nitrate solution, whereas the dried nanocomposite beads have got a nitrate removal efficiency of ~ 68% in 1h from 100ppm nitrate solution. Continuous flow adsorption cum photocatalytic study was performed further using the oven-dried functional beads in which flow rate and bed height were varied while maintaining the concentration of feed solution as constant. A nitrate removal efficiency of 65% and an adsorption capacity of 4.1 mgg-1 were obtained for the CTA-F3 beads in the continuous flow adsorption cum photocatalysis experiment for up to 5h when using an inlet concentration of 100ppm, bed height 12cm, and flow rate 5.0mlmin-1. A representative fixed-bed column adsorption experiment conducted using CTA-F3 beads for the treatment of a real groundwater sample shows reasonable results for nitrate removal (71.7% efficiency) along with a significant removal rate for the other anions as well. Thus, the novel adsorbent/photocatalyst developed is suitable for the removal of nitrates from water due to the synergistic effect between Fe3O4, chitosan, and titanium dioxide.

Development of an asymmetric cellulose acetate-ionic liquid P6,6,6,14[PHOS] gel membrane for the perstraction of succinic acid from a model fermentation solution of yarrovia lipolytica

This study introduces a novel approach to separate succinic acid (SA) from fermentation mixtures using an asymmetric membrane based on the gelation of the ionic liquid [P6,6,6,14][PHOS] coated with two layers of cellulose acetate. The membrane was designed to explore the synergistic effect of polymer-ionic liquid interfaces according to the solution-diffusion theory. The gelation of the ionic liquid was achieved using 12-hydroxystearic acid at a concentration of 1.5%, allowing the use of ionic liquid gels as new materials for the generation of membranes. The perstraction performance of the membrane was evaluated over 5 h at two different temperatures (25°C and 37°C), with an initial feed solution concentration of 50 kg m−3 for SA and glycerol and pure water as a receiving phase., Several flow rates and phase-volume ratios were studied anda mass transfer model based on the resistance-in-series theory was assessed to understand the behavior of each mass transfer stage considering the distribution in each interphase. Interestingly, optimal perstraction results were obtained at 37°C, with an average transmembrane flux of 0.22 kg m-2h−1 for SA, an extraction percentage of 43.1% for SA and 0.7% for glycerol, and a SA/glycerol selectivity of 54.98. Besides presenting a novel composite membrane, this study reports pioneering perstraction outcomes, highlighting its potential as an innovative SA separation strategy and structured new materials for selective extractions.

Biomimetic interlayer brought unexpected enhancement in permeability and rejection of polyamide nanofiltration membrane

Construction of interlayer between porous substrate and polyamide (PA) layer has been proved to be an effective way in improving membrane separation performance by the regulation of membrane structure and chemical properties. In present study, biomimetic material—1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE) lipid bilayer was selected to serve as the interlayer prepared by suction filtration due to its unique advantages such as smooth, continuous, uniform and hydrophilic surface. The results showed that DOPE interlayer effectively lowered the diffusion rate of piperazine (PIP) from membrane surface to organic phase and thus contributing to the thinner and smoother PA layer. The permeability of the interlayer-based PA membrane reached 35.9 L/m2·h·bar, which was 190 % higher than pure PA NF membranes. More important, the interlayer-based PA membrane exhibited excellent Na2SO4 rejection about 99.8 % accompanied by a good separation selectivity between univalent and bivalent ions. Besides, the interlayer-based PA membrane possessed good stability to the changes of operating pressure, concentration and pH of feed solution, and the long-term NF test. Meanwhile, it performed well in removing NTU, TOC, Mg2+ and SO42− in the treatment of surface water and showed its potential in the practical application. In all, the present work brought new interlayer material in fabricating high-performance NF membrane.

Preparation of PVDF-nSiO2/PVSQ high-flux composite membrane by chemical grafting and separation of composite brine by membrane distillation

The large-scale application of membrane distillation (MD), an important method for desalting seawater, is limited due to membrane fouling. In this study, ethyl orthosilicate (TEOS) was polymerized to obtain different nSiO2 particles. Vinyl triethoxysilane (VTES) was hydrolysed and polycondensation was used to produce spherical polyethylene-sesquioxane (PVSQ) microparticles, which were modified to construct micro/nano particles. Then grafted on the surface of polyvinylidene fluoride (PVDF) composite membrane. The low-surface-energy hydrophobic groups present on the surfaces of the vinyl and ethoxy particles greatly enhanced the membrane hydrophobicity. The particle size of nSiO2 can change the properties of the membrane. The separation performance of the membrane was tested by direct contact membrane distillation (DCMD). In the separation of a constant concentration of feed solution (3.5 wt% NaCl), the membrane flux was relatively stable at 23.8 kg·m−2·h−1, and the salt interception rate reached 99.99 %. In the subsequent separation of a salt/humic acid solution, the flux remained stable and the good anti-fouling performance indicating that this system outperformed the unmodified membrane. Finally, the effect of different cations on the water diffusivity was studied using a molecular simulation method. Both Ca2+ and Mg2+ reduced the diffusion coefficient of water. However, when these two ions were present simultaneously, Ca2+ inhibited the binding of Mg2+ to water, and the diffusion coefficient of water increased. This study provides a novel approach for preparing hydrophobic membranes for the separation of complex brines.

Accumulation of Particles in an Annular Centrifugal Contactor Cascade and the Effect upon the Extraction of Nitric Acid

Centrifugal contactors (CCs) are a technology candidate for the development of advanced reprocessing flowsheets. While they offer many advantages, such as process intensification, there are still uncertainties regarding their industrial deployment. The presence of particles in the process streams in particular may present a challenge to both performance and operability. Preliminary studies have been undertaken to evaluate the accumulation of particles in the contactors and the effect upon the extraction behaviour of nitric acid. Aluminium oxide (Al2O3) particles were suspended in the aqueous feed solution during the operation of a three-stage, 40 mm diameter CC cascade. The presence of insoluble solid particles in the aqueous feed, up to 7 g/L, were not observed to affect phase separation and entrainment under the experimental conditions investigated. The particles were centrifuged out of solution and accumulated as a thin cake/bed in the rotors of each stage. This work also illustrates that particles do entrain through the cascade. The predominant effect on the rate of accumulation was particle concentration in the aqueous feed solution, and increasing solids loading was observed to have an impact upon the extraction of nitric acid across the cascade.

Concentration properties of biopolymers via dead-end forward osmosis

Extracellular polymeric substances (EPSs) in excess sludge of wastewater treatment plants are valuable biopolymers that can act as recovery materials. However, effectively concentrating EPSs consumes a significant amount of energy. This study employed novel energy-saving pressure-free dead-end forward osmosis (DEFO) technology to concentrate various biopolymers, including EPSs and model biopolymers [sodium alginate (SA), bovine serum albumin (BSA), and a mixture of both (denoted as BSA-SA)]. The feasibility of the DEFO technology was proven and the largest concentration ratios for these biopolymers were 94.8 % for EPSs, 97.1 % for SA, 97.8 % for BSA, and 98.4 % for BSA-SA solutions. An evaluation model was proposed, incorporating the FO membrane's water permeability coefficient and the concentrated substances' osmotic resistance, to describe biopolymers' concentration properties. Irrespective of biopolymer type, the water permeability coefficient decreased with increasing osmotic pressure, remained constant with increasing feed solution (FS) concentration, increased with increasing crossing velocity in the draw side, and showed little dependence on draw salt type. In the EPS DEFO concentration process, osmotic resistance was minimally impacted by osmotic pressure, FS concentration, and crossing velocity, and monovalent metal salts were proposed as draw solutes. The interaction between reverse diffusion metal cations and EPSs affected the structure of the concentrated substances on the FO membrane, thus changing the osmotic resistance in the DEFO process. These findings offer insights into the efficient concentration of biopolymers using DEFO.

Techno-economics of multi-stage reverse electrodialysis for blue energy harvesting

Multi-stage reverse electrodialysis (MSRED) offers a promising way for efficient salinity gradient energy harvesting. Here, an improved model of the MSRED system under serial control strategy is proposed. The technical–economic analysis is conducted with considering discount, depreciation and different regional tax and electricity price levels under the maximum net power output conditions. Results reveal that net power output and energy efficiency both increase first with increasing stage numbers, reach their maximum values, and then decrease. For 5 M/0.05 M solutions, the optimal net power output of 4.98 kW is obtained at the stage number n = 12. The optimal stage number corresponding to the maximum net power increases with increasing feed solution concentrations. Due to the compromise between net power generation and capital cost, there exist optimal stage numbers leading to the lowest LCOE and largest NPV, respectively. Higher feed solution concentration can significantly decrease the system LCOE and increase the NPV. The optimal stage number corresponding to the maximum NPV increases with increasing feed solution concentrations. In Germany, for 5 M/0.05 M solutions, the lowest LCOE of 0.061 €·kWh−1 is achieved at n = 3 while the highest NPV over the system lifecycle of 52,005 € is obtained at n = 8. Lower tax, higher electricity price, appropriate membrane price and stage numbers, and high salinity gradient sources can significantly accelerate the commercial completeness of the MSRED systems.

Simulations of novel mixed-patterned membrane surfaces: Enhanced hydrodynamics and concentration polarization to mitigate fouling in water treatment

The accumulation of particles and salt ions on the membrane surface is the main challenge in different water treatment applications, such as microfiltration (MF), ultrafiltration (UF), reverse osmosis (RO), and nanofiltration (NF), undesirably affecting the membrane's water permeance and salt rejection. This study used computational fluid dynamics (CFD) simulations to investigate novel mixed triangular-rectangular (mixed tri-rec) shaped patterned membrane surfaces toward reducing membrane fouling and increasing water flux. These outcomes were compared with previously reported flat, triangular (tri), and rectangular (rec) patterned surfaces. The fluid flow behavior and transport of diluted species under laminar flow conditions were investigated in the vicinity of different patterned membrane surfaces. Parameters such as diffusion coefficient, pressure difference across the membrane, and feed solute concentration remained fixed during the investigation. The key parameters evaluated were the velocity streamline profile, shear stress, concentration polarization (CP), and permeate flux (PF). The overall wall shear stress (OWSS) and local wall shear stress (LWSS) were also evaluated, and unobvious behavior was observed in both cases. Also, interesting behavior emerged when the averaged CP and PF were analyzed as a function of varying crossflow velocities. Further, the results indicate that pattern geometry significantly affects the PF. Additional simulations varying pattern sizes parametrically were performed, and the influence of pattern size ratio on CP, PF, and consequently, boundary layer thickness was investigated. Overall, this study presents a new understanding of fouling mitigation and enhanced permeate flux while comparing a novel mixed tri-rec-shaped membrane surface with previously reported homogeneous patterned surfaces.

High performance and antifouling zeolite@polyethersulfone/cellulose acetate asymmetric membrane for efficient separation of oily wastewater

Microfiltration membranes have emerged as a promising alternative for oily wastewater treatment due to their high efficiency, low cost, and ease of operation. In this study, polyethersulfone (PES), cellulose acetate (CA), and 4A zeolite were blended to fabricate asymmetric membranes by the phase inversion technique and examined in oily wastewater treatment. Kerosene was chosen as a model polluting oil. The fabricated pure PES membrane (P), PES membranes incorporating 4A zeolite (ZP), PES membrane blended with CA (PC), and PES/CA blended membranes with 4A zeolite (ZPC) were characterized using field emission scanning electron microscopy, atomic force microscopy, Fourier-transform infrared spectroscopy, porosity, and contact angle to study the structure properties of these membranes. The performance of membranes was examined by water permeation, oil permeation flux, oil rejection, flux recovery ratio, and relative flux reduction. The ZPC membranes showed the highest performance in comparison with other prepared membranes. Incorporating 4A zeolite nanoparticles with 0.5 wt% into the PES/CA blended membrane significantly enhanced the microfiltration performance and decreased the contact angle of the P membrane from 70° to 29.8°. The effect of operation parameters such as transmembrane pressure (1–4 bar), feed temperature (25–50 ºC), and concentration of oil feed solution (250–1000 mg/L) on the permeation flux and oil rejection was studied on the PES/CA blended membrane containing 0.5 wt% 4A zeolite (0.5%ZPC). The 0.5%ZPC membrane showed improved porosity of 87.7% and it gave the highest value of pure water flux of 91.1 L/m2.h, oil permeation flux of 75.55 L/m2.h, maximum oil rejection of 98.8%, flux recovery ratio of 97.7%, and relative flux reduction of 21.8%. The permeation flux given by the 0.5%ZPC membrane was improved by about 8 times that of the P membrane. Re-usability studies verified the durability of the blended membranes and their performance in oily wastewater treatment.

Synthesis and characterization of an innovative sodium alginate/polyvinyl alcohol bioartificial hydrogel for forward-osmosis desalination.

Recently, hydrogels have been widely applied as draw agents in forward osmosis (FO) desalination. This work aims to synthesize bioartificial hydrogel from a blend of sodium alginate (SA) and polyvinyl alcohol (PVA) using epichlorohydrin (ECH) as a crosslinker. Then this prepared hydrogel was applied as a draw agent with cellulose triacetate membrane in a batch (FO) cell. The effects of the PVA content in the polymer blend and the crosslinker dose on the hydrogel's swelling capacity were investigated to optimize the hydrogel's composition. Furthermore, the water flux and the reverse solute flux of the optimum SA/PVA hydrogel were evaluated in a batch (FO) unit under the effect of the hydrogel's particle size, feed solution (FS) temperature, FS concentration, and membrane orientation. Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray diffraction (XRD) and compression strength tests were used to characterize the prepared hydrogel. Results revealed that the equilibrium swelling ratio (%) of 5228 was achieved with a hydrogel that had 25% PVA and a crosslinking ratio of 0.8. FO experiments revealed that the maximum water flux of 0.845 LMH achieved, when distilled water was used as FS, average hydrogel's particle size was 60µm, and the FS temperature was 40°C.

A Study on the Treatment and Recovery of Sodium Sulfate (Na&lt;sub&gt;2&lt;/sub&gt;SO&lt;sub&gt;4&lt;/sub&gt;) Generated When Recovering Valuable Metals (Ni, Co, Mn, Li) from Waste Lithium Ion Batteries(LIBs)

Concerns have arisen regarding the high concentrations of sodium sulfate in wastewater resulting from the waste Li-ion battery wet recycling process. In addressing this issue, Bipolar electrodialysis was employed to desalinate high-concentration sodium sulfate and recover it as sulfuric acid and sodium hydroxide. The investigation encompassed various experimental variables, such as applied voltage (maintained at a constant level), feed solution concentration, the initial concentrations of sulfuric acid and sodium hydroxide, and volume ratio (F/A/B). Optimal conditions were determined by assessing water migration (%), the recovery rates (%) of sulfuric acid and sodium hydroxide, concentration of the recovered substances, process time, and energy consumption. A higher applied voltage was found to reduce process time while increasing energy consumption, with the 25 V condition considered preferable. When utilizing a high-concentration feed solution, energy consumption rises; however, it decreases per unit of processed solution, rendering a 1.30 M Na&lt;sub&gt;2&lt;/sub&gt;SO&lt;sub&gt;4&lt;/sub&gt; feed solution preferable. Increasing initial concentrations of sulfuric acid and sodium hydroxide substantially prolonged process time and increased energy consumption, emphasizing the advantage of commencing with low initial concentrations. Adjusting the volume ratio facilitated the concentration and recovery of sulfuric acid and sodium hydroxide with minimal impact on process time or energy consumption. Under the identified optimal conditions, the recovery of 1.70 M sulfuric acid and 2.44 M sodium hydroxide was achieved.

Isopropanol concentration by osmotically assisted reverse osmosis

Isopropanol (IPA) is a versatile solvent used in a wide range of industrial and consumer applications, and its disposal may pose high costs and environmental concerns. In this work, the osmotically assisted reverse osmosis (OARO) technology was employed to demonstrate the effective treatment and concentration of IPA wastewater. The effect of various operating parameters, including feed solution concentration, number of membrane modules, flow rate, and applied pressure, was systematically investigated. Both permeance and IPA rejection decreased with an increase in IPA concentration, due to increase of feed solution osmotic pressure and occurrence of membrane swelling. By adjusting the feed flow rate and applied pressure, we can effectively control the final IPA concentration. Specifically, lowering the feed flow rate will result in higher IPA concentration, and increasing the applied pressure will also lead to higher IPA concentration. Long-term operational stability was also investigated, and results showed that the OARO process could maintain stable operation over an extended period of 180 days. Lastly, real IPA wastewater sourced from an electronics devices factory was treated using the OARO system and the wastewater sample was concentrated for more than four times. The results of this work exhibit the great practical application potential of the OARO process for the concentration of IPA wastewater.

Synthesis and characterization of an innovative sodium alginate/flaxseed gum green hydrogel for forward osmosis desalination

Recently, fresh water resources have been limited globally. Thus, desalination has been the most recommended solution to overcome this issue. Forward osmosis (FO) is an affordable and developing desalination technique. In this current study, a cutting-edge green hydrogel was prepared from a polymer blend of flaxseed gum (FG) and sodium alginate using epichlorohydrin (ECH) as a crosslinker and polyethylene glycol (PEG) as a semi-interpenetrating network polymer. The impact of PEG incorporation on the hydrogel’s response was investigated, and the influence of different mass contents of FG and ECH on the swelling measurements of the hydrogel was studied to optimize the composition of the hydrogel. The optimum hydrogel was characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, and X-ray diffraction and the compressive strength test. Furthermore, the behavior of the present hydrogel was examined as a draw agent in a batch FO unit. The water flux and the reverse solute flux were measured at various values of average hydrogel particle size and feed solution (FS) temperature and concentration. The optimal hydrogel of 0.3 PEG/polymer blend mass ratio, 12% FG, and 0.95 ECH/polymer blend mass ratio exhibits a swelling ratio (%) of 1800 after an hour and an equilibrium swelling ratio (ESR) (%) of 5300. The results of the FO experiments revealed that raising FS temperature and reducing FS concentration and average hydrogel particle size enhance water flux.

On the evaluating membrane flux of forward osmosis systems: Data assessment and advanced intelligent modeling.

As an emerging desalination technology, forward osmosis (FO) can potentially become a reliable method to help remedy the current water crisis. Introducing uncomplicated and precise models could help FO systems' optimization. This paper presents the prediction and evaluation of FO systems' membrane flux using various artificial intelligence-based models. Detailed data gathering and cleaning were emphasized because appropriate modeling requires precise inputs. Accumulating data from the original sources, followed by duplicate removal, outlier detection, and feature selection, paved the way to begin modeling. Six models were executed for the prediction task, among which two are tree-based models, two are deep learning models, and two are miscellaneous models. The calculated coefficient of determination (R2 ) of our best model (XGBoost) was 0.992. In conclusion, tree-based models (XGBoost and CatBoost) show more accurate performance than neural networks. Furthermore, in the sensitivity analysis, feed solution (FS) and draw solution (DS) concentrations showed a strong correlation with membrane flux. PRACTITIONER POINTS: The FO membrane flux was predicted using a variety of machine-learning models. Thorough data preprocessing was executed. The XGBoost model showed the best performance, with an R2 of 0.992. Tree-based models outperformed neural networks and other models.

A study on the influence of feed and draw solution concentrations on the performance of the pilot-scale forward osmosis-membrane distillation system

The increasing demand for freshwater and scarcity of natural sources of freshwater have led the world to turn to seawater as a main source to produce freshwater through conventional desalination processes. Multi-stage flash distillation (MSF) and reverse osmosis (RO) technologies are currently being utilized in the existing desalination plants. However, these technologies are energy-intensive and have their own limitations such as scaling and fouling. Therefore innovation in non-conventional desalination technologies has produced a number of promising systems including the newly developed integrated membrane system using forward osmosis (FO) and membrane distillation (MD). The scope of this study will assess the viability and efficiency of an FO-air gap MD (AGMD) integrated system of capacity 5 m3/day for desalination application using different concentrations of NaCl as feed and draw solutions. The FO-AGMD system performance was majorly evaluated in terms of water recovery. At a fixed DS concentration of NaCl at 70000 ppm, the highest water recoveries in the range of 50–60% were observed for the lowest FS concentration i.e. DI water attributed to the highest ∆Π difference across the FO membrane. The increased DS concentration at a fixed concentration of the FS decreased the average water recovery of the system attributed to the unique design of the FO-AGMD system. For the fixed NaCl concentration of FS at 5000 ppm, the FO-MD process with 35,000 ppm solution of NaCl as DS showed higher water recovery in the range of 46–51% compared to the DS concentration of 150,000 ppm NaCl, which showed water recovery in the range of 30–41% at the operating temperature of MD at 85 °C.

Effect of pH, NaCl concentration, and mAb concentration of feed solution on the filterability of Planova™ 20N and Planova™ BioEX.

Virus filtration is one of the most important steps in ensuring viral safety during the purification of monoclonal antibodies (mAbs) and other biotherapeutics derived from mammalian cell cultures. Regarding the various virus retentive filters, including Planova filters, a great deal of data has been reported on the virus retention capability and its mechanism. Along with the virus retention capability, filterability is a key performance indicator for designing a robust and high-throughput virus filtration step. In order to obtain higher filterability, optimization of the feed solution conditions, and filter selection is essential; however, limited data are available regarding the filtration characteristics of Planova filters. Furthermore, for Planova 20N and Planova BioEX, the virus retention characteristics were reported to differ due to their respective membrane materials and layer structures. Whether these filters differ in their filtration characteristics is an interesting question, but no comparative evaluations have been reported. In this study, the filterability of the two filters was investigated and compared using 15 feed mAb solutions of a single mAb selected by design of experiments with different combinations of pH, NaCl concentration, and mAb concentration. The filterability of Planova 20N was affected not only by the feed solution viscosity, but also by the mAb aggregate content of the feed mAb solution and mAb-membrane electrostatic interactions. In contrast, the filterability of Planova BioEX decreased under some buffer conditions. These findings and the established design spaces of these filters provide valuable insights into the process optimization of virus filtration.

A hybrid process combining ion exchange resin and bipolar membrane electrodialysis for reverse osmosis remineralization

A new reverse osmosis (RO) permeate remineralization process combining ion exchange resin and bipolar membrane electrodialysis (BMED) was developed. Its feasibility for hardness ions recovery and RO permeate remineralization was investigated. The effect of several operation conditions on the efficiency of the combined remineralization process was studied. Highly efficient cation exchange resin loading was achieved at a low flow rate and low feed solution concentration. The recovered calcium purity and yield considerably improved under gradient elution methods in comparison with commonly applied conventional isocratic elution methods using the same eluent quantity. The purity of the produced acid and base using BMED dropped noticeably with increasing feed NaCl concentration, presumably related to decreased permselectivity of the ion-exchange membranes. The drop in the purity of the calcium recovered when eluting the cation exchange resin with BMED-produced HCl in comparison with commercially available acid at 50 % yield was shown not to affect the remineralization process, where a dilution factor could be applied. This study confirmed the technical feasibility of the developed process for RO permeate remineralization. However, its application can be limited by the water source characteristics, the energy-intensive bipolar membrane process, and applied operational conditions, where more investigation is still needed.

Integration of electrochemical processes in a treatment system for landfill leachates based on a membrane bioreactor

The use of electrocoagulation (EC) and anodic oxidation (AO) processes was studied for improving a treatment system for landfill leachates based on a membrane bioreactor (MBR) and a nanofiltration step. The main limitation of the current full-scale system is related to the partial removal of organic compounds that leads to operation of the nanofiltration unit with a highly concentrated feed solution. Application of the EC before the MBR participated in partial removal of the organic load (40 %) with limited energy consumption (2.8 kWh m−3) but with additional production of iron hydroxide sludge. Only AO allowed for non-selective removal of organic compounds. As a standalone process, AO would require a sharp increase of the energy consumption (116 kWh for 81 % removal of total organic carbon). But using lower electric charge and combining AO with EC and MBR processes would allow for achieving high overall removal yields with limited energy consumption. For example, the overall removal yield of total organic carbon was 65 % by application of AO after EC, with an energy consumption of 21 kWh m−3. Results also showed that such treatment strategy might allow for a significant increase of the biodegradability of the effluent before treatment by the MBR. The MBR might then be dedicated to the removal of the residual organic load as well as to the removal of the nitrogen load. The data obtained in this study also showed that the lower electric charge required for integrating AO in a coupled process would allow for strongly decreasing the formation of undesired by-products such as ClO3− and ClO4−.