Osmotic Membrane Distillation Research Articles

Sustainable Low‐Alcohol Beer Production by Combination of Membrane Osmotic Distillation and Pervaporation

AbstractMembrane osmotic distillation (OD) is applied in this work for the partial dealcoholization of beer (5.2 v/v% alcohol content) to diminish its ethanol content by around 50% giving rise to a low alcohol beer. A compromise is sought between the low alcoholic degree achieved and beer sensory properties. Moreover, the feasibility of the membrane OD process intensification is studied thanks to its combination with membrane pervaporation (PV). Two successive PV stages, one hydrophobic and the other hydrophilic, allow the production of recycled water (with less than 0.5 wt% ethanol) for the membrane OD operation and bioethanol (99% ethanol) as valuable byproduct.

Enzymatic Synthesis of Prebiotic Carbohydrates from Lactose: Integration of Osmotic Membrane Distillation with Batch Reactor System

AbstractThis study aimed to enhance galactooligosaccharide (GOS) yield by maintaining high lactose concentration levels using osmotic membrane distillation (OMD) throughout the synthesis. The main problem influencing GOS yield during transgalactosylation is the decrease of lactose concentration over extended reaction periods. By integrating OMD with a continuous stirred batch reactor, water was progressively removed from the reaction medium. Compared to a standard batch reactor, the OMD-integrated system not only increased GOS yield by a maximum of 20.1% but also reduced the time needed for equivalent lactose conversion about 15–90 min. This integration particularly boosted the formation of longer-chain GOS. A consistent GOS yield of 67% was achieved, with up to 28% lactose conversion, surpassing the non-integrated reactor’s performance. The proposed reactor design shows promise for enhancing GOS production efficiency while concurrently concentrating the reaction medium in a single step.

Process optimization of osmotic membrane distillation for the extraction of valuable resources from water streams

The rising demand for sustainable wastewater management and high-value resource recovery is pressing industries involved in, e.g., textiles, metals, and food production, to adopt energy-efficient and flexible liquid separation methods. The current techniques often fall short in achieving zero liquid discharge and enhancing socio-economic growth sustainably. Osmotic membrane distillation (OMD) has emerged as a low-temperature separation process designed to concentrate valuable elements and substances in dilute feed streams. The efficacy of OMD hinges on the solvent’s migration from the feed to the draw stream through a hydrophobic membrane, driven by the vapor pressure difference induced by both temperature and concentration gradients. However, the intricate interplay of heat and mass processes steering this mechanism is not yet fully comprehended or accurately modeled. In this research, we conducted a combined theoretical and experimental study to explore the capabilities and thermodynamic limitations of OMD. Under diverse operating conditions, the experimental campaign aimed to corroborate our theoretical assertions. We derived a novel equation to govern water flux based on foundational principles and introduced a streamlined version for more straightforward application. Our findings spotlight complex transport-limiting and self-adjusting mechanisms linked with temperature and concentration polarization phenomena. Compared with traditional methods like membrane distillation and osmotic dilution, which are driven by solely temperature or concentration gradients, OMD may provide improved and flexible performance in target applications. For instance, we show that OMD—if properly optimized—can achieve water vapor fluxes 50% higher than osmotic dilution. Notably, OMD operation at reduced feed temperatures can lead to energy savings ranging between 5 and 95%, owing to the use of highly concentrated draw solutions. This study underscores the potential of OMD in real-world applications, such as concentrating lithium in wastewater streams. By enhancing our fundamental understanding of OMD’s potential and constraints, we aim to broaden its adoption as a pivotal liquid separation tool, with focus on sustainable resource recovery.

PVDF hydrophobic hollow fiber membrane modules for partial dealcoholization of red wine by osmotic distillation as a strategy to minimize the loss of aromas

Tempranillo red wines were partially dealcoholized (−3 v/v%) by osmotic distillation (OD) with membranes. First, polypropylene (PP) Liqui-Cel3M (3M) hollow fiber membrane modules were applied at 11 and 15 °C to study the effect of the removal of ethanol on the aroma of a certain wine. The influence of both temperatures was evaluated in terms of ethanol flux and aroma losses. Afterwards, two additional wines with different compositions were dealcoholized. The impact of the initial concentration of aromas on achieving a final product with an appealing aroma profile was studied, displaying the three wines a comparable aroma retention. Membrane OD was carried out with two additional hollow fiber membrane modules: another PP module (Zena) with a higher pore size, and a superhydrophobic PVDF module (Polymem). The latter gave rise to a partial dealcoholized wine with an aroma profile very similar to that of the pristine wine.

A novel approach for sterilization and concentration of traditional functional drinks: Membrane‐based nonthermal processes

AbstractThe applicability of microfiltration (MF) and osmotic membrane distillation (OMD) for sterilization and concentration of traditional functional drink constituents, such as Curcuma xanthorrhiza, ginger, lime, Java tea, and sappan wood extracts, was evaluated in this study. MF showed excellent performance in microorganisms elimination, turbidity reduction, and maintaining antihyperglycemic activity performance. However, a reduction of total phenol and antioxidant activity were observed due to the retention by MF. Fouling in MF was challenging and resulted in rapid flux decline. The concentration of sterilized extracts by OMD operation resulted in a concentration factor of 1.15, 1.13, 1.10, 1.24, and 1.24 for ginger, lime, C. xanthorrhiza, Java tea, and sappan wood, respectively. The active compounds were well preserved, with a maximum of 20% reduction compared to sterilized extracts. Despite insignificant foulant deposition, the OMD flux in tests using C. xanthorrhiza, ginger, and lime as the feed decreased over time, indicating reduced driving force.Practical applicationsThe application of membrane technology for juices and liquid foods sterilization and concentration has been widely researched. In this research, we evaluated the performance of MF and OMD for the sterilization and concentration of traditional functional drinks. The results indicated that the functional drink can be sterilized by MF with excellent preservation of the active compounds, such as those responsible for the antihyperglycemic and antioxidant activities. The OMD could also concentrate the traditional functional drink, even though concentration polarization posed a challenge to flux stability. The degradation of phenolic compounds and antioxidant activity of the concentrated traditional functional drink was at a minimal value, indicating the promising application of MF and OMD. We believe this article provides new and exciting insights to push forward the sterilization and concentration process in industrial scale.

Concentration of phycocyanin and coffee extracts in aqueous solutions with osmotically-assisted membrane distillation

Osmotic membrane distillation (OMD) is a dewatering process that exploits combined temperature and osmotic pressure gradients to drive water vapor fluxes under mild operation conditions. In this study, the feasibility of OMD is evaluated for the concentration of phycocyanin and coffee extract solutions, with the goal to safeguard the quality of the extracts. Different feed solution temperatures were studied, namely, 35 °C, 45 °C, 55 °C, while keeping a concentration of 4 M CaCl2 in the extraction solution. The target concentration factor was set to 4, equivalent to a water recovery rate of 75 %. The results suggest that a temperature equal to or below 45 °C should be chosen for the concentration of phycocyanin to prevent degradation and to minimize fouling, while higher temperatures may be used for the recovery of the coffee extract. The combined gradients provided water fluxes around or above 4 L m−2h−1 with both extracts under relatively mild conditions, even at high concentration factors. Qualitative membrane fouling inspection was corroborated by estimating the fraction of productivity lost due to fouling, which was larger for higher feed temperatures and for the phycocyanin extracts, and had values between roughly 20 and 70 %. Results also suggest that the quality of the extracts was maintained, based on the measured purity and content of the target compounds in the concentrated solutions. Specifically, no trace of extraneous compounds was found, and no salt passage was observed from the extraction solution to the feed solution, suggesting that OMD has the potential to concentrate sensitive components.

CFD simulation of osmotic membrane distillation using hollow fiber membrane contactor: Operating conditions and concentration polarization effects

Inorganic salts, when present in high concentrations, can disrupt the osmotic balance of aquatic organisms, leading to physiological and ecological harm. Osmotic membrane distillation (OMD) is an emerging technique for recovering inorganic salts from wastewater. The process involves the transfer of water vapor from a feed solution (FS) to a permeate stream due to the difference in vapor pressure across a hydrophobic membrane. It thus results in a concentrated solution at the feed outlet and purified water at the permeate side. OMD is preferred due to its straightforward scale-up and low energy requirements. In this research, a steady state 2-D axisymmetric computational fluid dynamics (CFD) model is developed to study the recovery of sodium carbonate (Na2CO3) from aqueous feed solution through OMD in a hollow fiber membrane contactor (HFMC). Aqueous sodium chloride (NaCl) solution was taken as an osmotic solution (OS). The numerical convection-diffusion mass, momentum transport, and Happel equations were scripted in COMSOL Multiphysics™ version 6.0 software. The model computed the water transport from FS to OS. Computed water flux well matched with the literature based experimental results. Simulations were carried out to investigate the parametric effects, including Reynold’s number, FS and OS concentration and the module geometrical parameters to establish an optimized operating conditions and module geometry and to achieve the desired FS concentration. Results showed that a 2-fold rise in OS concentration increased the transmembrane water flux 4-fold. However, the flow rates of both FS and OS did not significantly affect the flux. On the other hand, concentration polarization (CP) showed dependence on the FS concentration, tortuosity, and Reynolds number. A membrane tortuosity of 1.6, feed concentration of 75 g L−1, OS concentration of 300 g L−1, and a FS Reynolds number in the turbulent flow range can result in higher transmembrane flux and lower chances of CP development.

State-of-the-art Membrane Processing of Solution Rich in Phenolic Compounds

Polyphenols and phenolic acids extracted from plants are natural antioxidants with high market value. However, they are susceptible to thermal processes, and a significant loss throughout food and beverage processing has been widely reported. This work reviews the state-of-the-aft membrane processing of the solution rich in phenolic compounds. Novel membrane processing allows phenolic concentration and water recovery simultaneously without using hazardous chemicals and high temperatures. Comparing pressure-driven membrane filtration processes with the advanced membrane processes at the low pressure in this review allowed the proper process selection to concentration phenolic coumpounds. Pressure-driven membrane filtration processes, namely microfiltration, ultrafiltration, nanofiltration, and reverse osmosis, have been studied. Nanofiltration membranes offer high retention of polyphenols due to their matching molecular weight cut-off. Osmotic distillation, membrane distillation and forward osmosis are membrane processes operated at low pressure. Osmotic distillation and forward osmosis require drawing solutions with osmotic pressure differences to separate water from phenolic compounds. A similar separation is attained in membrane distillation by creating vapour pressure differences. Membrane distillation without drawing solution is recommended since membrane fouling can be mitigated using superhydrophobic membranes with self-cleaning properties.

Pervaporation of the low ethanol content extracting stream generated from the dealcoholization of red wine by membrane osmotic distillation

This paper presents as main contribution the combination of membrane osmotic distillation (OD) to dealcoholize red wine with hydrophobic-hydrophilic pervaporation (PV) carried out to add value to the wastewater (extracting water) produced in OD, recycling water and generating bioethanol. Membrane OD with a commercial polypropylene hollow fiber module was applied to partially dealcoholize red wine from 14.0 to 11.0 v/v% ethanol. The OD extracting water, containing only ca. 5.3 wt% ethanol, was treated by sequential PV with both hydrophobic (PDMS or zeolite silicalite-1) and hydrophilic (zeolites mordenite or faujasite) membranes. This hydrophobic-hydrophilic PV produced two main products: bioethanol (recovering 88% of the ethanol removed from the wine) and a 99.4 wt% water-rich product. This water-rich product, with a very low ethanol content, was used as extracting water in the OD, giving rise to an analogous partially dealcoholized wine, in terms of aroma contents (as determined by gas chromatography for 25 compounds), to that achieved when using fresh water.

Selective and high-efficient removal of tetracycline from antibiotic-containing aqueous solution via combining adsorption with membrane pre-concentration

The antibiotics in the livestock sewerage are responsible for antimicrobial resistance, causing a global public health crisis and necessitating high-efficient and environmental-friendly antibiotic treatment processes. Herein, one membrane pre-concentration and MOF-based selective adsorption hybrid system is proposed to high-efficiently remove tetracycline (TC) from the aqueous solution containing other two representative antibiotics (sulfamethoxazole (SMZ), and trimethoprim (TMP)) in the livestock sewage. In this work, two common MOFs-based materials (MIL-101-Fe and NH2-MIL-101-Fe) are employed as the adsorbents to selectively remove TC from the solution. Adsorption experiments showed that the selective coefficient of NH2-MIL-101-Fe for TC could reach up to 95 %, because of stronger interaction between TC and MIL-101s calculated via the theoretical simulation. Also, experimental results demonstrated that the desired operating conditions necessitated thermal input and pre-concentration operation. Accordingly, temperature-enhanced forward osmosis (T-FO) and temperature-enhanced osmotic membrane distillation (T-OMD) were proposed to concentrate the solution containing these three antibiotics in the cost-effective way where the fertilizer solution (KCl in this work) was used as the draw solution (DS) and diluted DS solution could be used in agricultural fertigation. Membrane pre-concentration experiments showed that TC, TMP, and SMZ could be theoretically concentrated in T-FO, but high TC and KCl leakage and inevitable water flux decline behavior significantly sacrificed the concentration efficiency, thereby initiating the application of T-OMD. Higher and more stable water flux occurred in T-OMD, and 99.76 % of antibiotic and KCl leakage could be mitigated compared to T-FO, thereby providing one option to high-efficiently remove antibiotics in livestock sewerage and achieve agricultural fertigation.

Toward anti-fouling properties and enhanced performance in separation process - carbon nanotubes - PVDF hybrids

The development of membranes with anti-fouling properties is one of the leading research paths for emerging membrane technology. In work, anti-fouling PVDF-based membranes were produced. The material engineering focused on the silanization, via molecules equipped either with one or three reactive groups, of the PVDF surface rich in hydroxyl (OH) moieties. Subsequently, carboxylic functionalized multi-walled carbon nanotubes (MWCNTs) were covalently attached to the silanized surfaces. For the first time, the chemically-covalently attached MWCNTs were used to tune the surface features of PVDF for fouling mitigation. All produced materials were characterized and utilized in osmotic membrane distillation for the juice dehydration process of raw apple juice. The tests covered morphology, changes in materials chemistry, wettability, surface charge, thermal stability, and fouling studies in the separation process with natural products. It was revealed that modification mitigates fouling significantly and improves the transport properties of the membranes. The membranes prepared during the modification with a one-reactive group modifier possessed better transport and materials features than hybrid materials grafted with silanes with three reactive groups. It was related to better self-organization of the grafted layers with a one-reactive group molecules.

Osmotic Membrane Distillation Crystallization of NaHCO3

A new crystallization process for sodium bicarbonate (NaHCO3) was studied, proposing the use of osmotic membrane distillation crystallization. Crystallization takes place due to the saturation of the feed solution after water evaporation on the feed side, permeating through the membrane pores to the osmotic side. The process operational parameters, i.e., feed and osmotic velocities, feed concentration, and temperature were studied to determine the optimal operating conditions. Regarding the feed and osmotic velocities, values of 0.038 and 0.0101 m/s, respectively, showed the highest transmembrane flux, i.e., 4.4 × 10−8 m3/m2·s. Moreover, study of the temperature variation illustrated that higher temperatures have a positive effect on the size and purity of the obtained crystals. The purity of the crystals obtained varied from 96.4 to 100% In addition, the flux changed from 2 × 10−8 to 7 × 10−8 m3/m2·s with an increase in temperature from 15 to 40 °C. However, due to heat exchange between the feed and the osmotic solutions, the energy loss in osmotic membrane distillation crystallization is higher at higher temperatures.

Investigating performance of fabricated electrospun polyethersulfone/Zeolite Y composite nanofibers in concentrate lemon juice by the osmotic membrane distillation process

AbstractThe main objective of this work is to increase the hydrophobicity of Polyethersulfone (PES) by adding Zeolite Y nanoparticles and investigating hydrophobicity, and the performance of fabricated membrane in concentrate fresh juice by the osmotic membrane distillation (OMD) process. Membranes containing 0, 0.04, 0.08, and 0.12 wt% of Zeolite Y nanoparticles were fabricated by the electrospinning method. Prepared membranes were characterized by scanning electron microscope (SEM), contact angle, and tensile. Pure water permeability was also measured for each membrane. Membranes were evaluated in the concentration of raw and fresh lemon juice (initial Brix of 6.75°) by the OMD process. Also, the concentrated juice color (a*, b*, L*, and ΔE) was measured for the most hydrophobic membrane. The contact angle of the electrospun membrane with 0 and 0.12 wt% of Zeolite Y nanoparticles were 138° and 160°, respectively, showing an increase in their surface hydrophobicity. Furthermore, the final concentration of juice during 5 hr of the OMD process with membranes containing 0, 0.04, 0.08, 0.12 wt% Zeolite Y and with the same stripping solution reached 33, 34.25, 34, 34.5°Brix, respectively. Finally, transpired that the time to reach the final concentration by the membrane containing 0.12 wt% nanoparticles was about 45 min shorter than the membrane without nanoparticles. The juice color had become redder, yellower, and darker. Adding nanoparticles and using the electrospinning method increases the hydrophobicity of the membrane. In the OMD process, as the hydrophobicity of the membrane increases, the duration of concentration decreases.Practical applicationsConsidering the various benefits of the fabricated membrane, it can be used to concentrate fruit juice in less time.

Techno-economic comparison between forward osmosis (FO) and temperature-enhanced osmotic membrane distillation (T-OMD) in agricultural fertigation

Forward osmosis (FO), as one energy-efficient desalination technology, had been intensively studied in agricultural fertilization to meet the demand of the water resource and the fertilizer for plant growth, showing good techno-economic benefit. As such, the energy-efficient temperature-enhanced osmotic membrane distillation (T-OMD) heated by low-grade thermal sources (i.e. solar energy) was firstly investigated in agricultural fertilization via techno-economic comparison with FO. The experimental investigation revealed that T-OMD in the agricultural fertigation can be endowed with quadruple advantages of high water flux at a high-temperature difference (>40 °C), low fertilizer loss, good compatibility for different fertilizers, and good feasibility to utilize some unconventional waters (i.e. wastewater, seawater, and seawater RO brine). Furthermore, a preliminary economic analysis showed that the membrane area and the price of the FO membrane module are two significant indicators to evaluate the economic feasibility of T-OMD. In detail, T-OMD must be more cost-effective than FO if the total membrane area is larger than 10,000 m2 under the same operating temperature configuration or dilution factor lower than 0.25 and permeate flux higher than 10,000 m3/h are satisfied under different operating temperature configurations. Based on the experimental investigation and economic analysis, T-OMD can provide an alternative pathway to achieve high-efficient and cost-effective agricultural fertigation.

Development of mass and heat transfer coupled model of hollow fiber membrane for salt recovery from brine via osmotic membrane distillation

BackgroundIn this research work, a coupled heat and mass transfer model was developed for salt recovery from concentrated brine water through an osmotic membrane distillation (OMD) process in a hollow fiber membrane contactor (HFMC).The model was built based on the resistance-in-series concept for water transport across the hydrophobic membrane. The model was adopted to incorporate the effects of polarization layers such as temperature and concentration polarization, as well as viscosity changes during concentration.ResultsThe modeling equations were numerically simulated in MATLAB® and were successfully validated with experimental data from literature with a deviation within the range of 1–5%. The model was then applied to study the effects of key process parameters like feed concentrations, osmotic solution concentration, feed, and osmotic solution flow rates and feed temperature on the overall heat and mass transfer coefficient as well as on water transport flux to improve the process efficiency. The mass balance modeling was applied to calculate the membrane area based on the simulated mass transfer coefficient. Finally, a scale-up for the MD process for salt recovery on an industrial scale was proposed.ConclusionsThis study highlights the effect of key parameters for salt recovery from wastewater using the membrane distillation process. Further, the applicability of the OMD process for salt recovery on large scale was investigated. Sensitivity analysis was performed to identify the key parameters. From the results of this study, it is concluded that the OMD process can be promising in salt recovery from wastewater.

Production of concentrated whey beverage by osmotic membrane distillation: Comparative evaluation of feed effect on process efficiency and product quality

Reconstituted whey powder (RCW), whey released after rennet-coagulation (PW) and microfiltration permeate of skim milk (IW) were used to produce concentrated beverage by osmotic membrane distillation (OMD). Effect of feed type on OMD performance and on final quality were evaluated. The use of IW not only promoted the greatest initial permeate flux but also reduced the operation time of OMD needed to reach 15.7 ± 0.4 ºBrix, as compared with PW and RCW. Based on mineral and amino acid intake, the concentrated IW corresponded to 50 ± 3% and 76 ± 5% of equal amount of skim milk, respectively. While IW beverage was a good source of isoleucine, PW beverage provided adequate intake of valine besides leucine and isoleucine. Along with the better process performance, the use of IW in OMD resulted in obtaining plain concentrated whey beverage having comparable nutritive value with the PW and the RCW, and better clarity.

Feasibility of thermo-sensitive P(NIPAM-MBA) hydrogels as novel stripping agents for osmotic membrane distillation

As thermo-sensitive hydrogels could absorb water quickly and squeeze the water out by their insoluble cross-linked networks under thermal stimulus, a novel osmotic membrane distillation (OMD) process was proposed for the first time. In the OMD process of this study, water vapor diffused across the membrane under the swelling pressure of thermo-sensitive hydrogels. Poly-N-isopropylacrylamide (PNIPAM) hydrogels with 0.02%, 0.1% and 0.5% N,N′-methylenebisacrylamide (MBA) were synthesized and incorporated into the OMD system. The hydrogel properties were characterized by UV–vis spectrophotometer, FTIR and SEM. The effects of MBA content, membrane characteristics, operating temperature on OMD flux were investigated. The initial fluxes for the 0.02%, 0.1% and 0.5% MBA hydrogel-OMD systems were 1.68, 1.09 and 0.76 kg/m2·h, respectively. And the hydrogels transformed to dehydrated state after 150 min of water absorption. The fastest water absorption rates for PNIPAM hydrogels with 0.02%, 0.1% and 0.5% MBA were obtained at the initial swelling ratios of 16, 14 and 12 folds, respectively. Besides, the optimal feed temperatures for the maximum flux were 40 °C, 50 °C and 50 °C for hydrogels with 0.02%, 0.1% and 0.5% MBA, respectively. The membranes with higher porosity and lower thickness demonstrated higher fluxes. According to our results, the swelling pressure of hydrogel acted as a driving force of the hybrid hydrogel-OMD system, and it was greatly affected by the hydrogel structure. Typically, a hydrogel with the balanced water absorbing and dewatering behaviors and a membrane with good mass transfer performance were two essential prerequisites for this process.

Molecular activation of fluoropolymer membranes via base piranha treatment to enhance transport and mitigate fouling – new materials for water purification

In this work, we introduce a reliable and direct method to activate fluoropolymers via integrating covalent labile ones for further modification. Basic piranha solution was used for the first time to functionalize polymeric surface with hydroxyl moieties. Subsequently, surfaces were modified with a varied molecular grafting. Materials were characterized and tested in several separation processes, including air-gap membrane distillation, osmotic membrane distillation, and microfiltration. This method deciphers surface architecture for various applications not only in membranes but also in variety of fields where functionalized fluoropolymers are employed. The work is also comparing membranes activated with acid and base piranha. The latter produced much more stable and resistant membranes with respect to the acid-treated ones. Systematic and material characterization on the molecular level, with the implementation of various spectroscopic, microscopic, and other techniques, was performed to prove and assess the generated, highly effective separation materials. The presented method opened the gate for fast and easy production of advanced functionalized fluoropolymers.

Electrospun hierarchical fibrous composite membrane for pomegranate juice concentration using osmotic membrane distillation

A dual-layered hierarchical fibrous composite (HFC) membrane with poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) as a thin active layer and poly(ethylene terephthalate) (PET) as a thick support layer was fabricated through electrospinning process. The membrane was tested for the concentration of clarified pomegranate juice through the osmotic membrane distillation (OMD) process. Experimental data showed that the transmembrane water flux until 8.621 ± 0.235 kg.m−2. h−1 was achieved at 25 ± 1 °C, which is about 4-fold higher than most of the reported work. The juice was successfully concentrated to 51.3 ± 0.052°Bx in a total time of 25.5 h. Membrane hydrophobicity analysis showed that the contact angle of the membrane dropped from 143.7°±3° to 120.1°±3°, while the liquid entry pressure decreased from 28.0 ± 1.8–25.0 ± 1.7 kPa, after the completion of the OMD process. Detailed morphology analysis depicted that pore blockage occurred due to the gel layer formation when the juice viscosity increased exponentially during the final stages of OMD process. Gel layer formation along with random fouling spots were found to be the main cause of drop in water vapor flux. However, simple washing of the membrane with deionized water effectively cleaned the fouling areas and removed the gel layer from the pores of the membrane. The first-ever application of dual-layered electrospun HFC membrane in the OMD concentration of pomegranate juice thus displayed a satisfactory performance, benefiting from the unique structures of the HFC membrane having the minimized mass transfer resistance and durable antifouling performance.

Mass transfer modelling of hollow fiber membrane contactor for apple juice concentration using osmotic membrane distillation

The present research study is based on theoretical and experimental investigation of hydrophobic porous hollow fiber membrane contactor (HFMC) module. The mass transfer diffusional model was developed for osmotic membrane distillation (OMD) and applied in apple juice concentration. The mathematical model was developed, taking into consideration the resistance-in-series concept for the mass transfer of water vapor molecules across the hydrophobic HFMC. The model was adapted to include the pore geometry, dimensionless numbers and concentration variation due to viscosity. The water vapor transport model was then simulated in MATLAB® and successfully validated with the experimental data. The model was applied to study the effects of driving forces for mass transfer and membrane porosity. Process parameters like juice concentration, stripping solution concentration, and Reynolds number were also studied to evaluate their effect on the overall mass transfer co-efficient and water vapor flux. The OMD experiments for the concentration of clarified apple juice were carried out in a laboratory-scale HFMC mini-module composed of two independent circuits, for stripping solution (CaCl2) and apple juice, respectively, in a total recycled mode. For the concentration of clarified apple juice, the evaporation flux ranged from 0.122 to 0.472 kgm−2h−1 resulting in a juice concentration of 30°Brix. The increase in pore diameter from 0.1 to 0.6 µm resulted in an increase in the mass transfer coefficient from 1.57 × 10−10 to 7.23 × 10−10 ms−1. Similarly, water vapor flux was increased from 0.02 to 0.50 kgm−2h−1, when the activity coefficient was changed from 0.1 to 0.5. Moreover, the results indicated that if the experimental parameters are carefully controlled, the simulation results can be used to predict the OMD process efficiency.