Membrane Configuration Research Articles

The Potential of Multi-stage Pressure Retarded Osmosis for Blue Energy Harvesting

Objective: This study aims to investigate the potential benefits of using different multi-stage and multi-pass flow configurations for improving the efficiency of the pressure-retarded osmosis (PRO) process, which generates energy by utilizing the difference in osmotic pressure between two salinity solutions. Methods: To achieve the objective, the study used a numerical simulation based on the solution diffusion model. A flat sheet forward osmosis membrane was simulated to investigate the potential of the proposed multi-stage PRO configurations. Results: The results of the simulation showed that the multi-stage PRO arrangement generated 18% more power than the single-stage PRO system. Additionally, the multi-pass arrangement resulted in a 58% increase in power output. Conclusion: This study provides important insights into the development of optimized PRO membrane and module configurations to improve the efficiency of energy generation. The findings highlight the potential benefits of multi-stage and multi-pass flow configurations, which can help to advance the field of renewable energy generation using the PRO process.

On equilibrium states of fluid membranes

The paper studies the equilibrium configurations of inextensible elastic membranes exhibiting lateral fluidity. Using a continuum description of the membrane's motions based on the surface Navier–Stokes equations with bending forces, the paper derives differential equations governing the mechanical equilibrium. The equilibrium conditions are found to be independent of lateral viscosity and relate tension, pressure, and tangential velocity of the fluid. These conditions suggest that either the lateral fluid motion ceases or non-decaying stationary flow of mass can only be supported by surfaces with Killing vector fields, such as axisymmetric shapes. A shape equation is derived that extends the classical Helfrich model with an area constraint to membranes of non-negligible mass. Furthermore, the paper suggests a simple numerical method to compute solutions of the shape equation. Numerical experiments conducted reveal a diverse family of equilibrium configurations. The stability of equilibrium states involving lateral flow of mass remains an unresolved question.

Multi-factorial central composite and complete mixing model for optimizing industrial biogas valorization

There is an increasing interest to use CO2 selective membrane to purify methane from natural or biogas because of the ease of access to this membrane configuration. The use of this membrane, however imposed an additional strain on the system because there was H2S contamination in the enriched product stream and requirement of high CO2/CH4 selectivity. To address this issue, an empirically validated complete mixing model integrated with a multi-factorial central composite design was applied to optimize the membrane process in methane enrichment from biogas containing H2S. The optimization resulted in 100% methane purity and 91.51% recovery using a methane selective membrane at 837.43 CH4/CO2 selectivity, 35.00 bar feed pressure, and 0.643 stage cut, without H2S contamination in the product stream. For comparison with CO2 selective membrane, methane purity of 91.74% and 90.26% recovery were achieved using CO2/CH4 selectivity of 1086.87, 31.82 bar feed pressure, and 0.310 stage cut. Methane selective membrane was performed better than CO2 selective membrane on four fronts, namely lower selectivity, higher CH4 recovery, higher CO2 recovery, higher CH4 purity, and the product stream was H2S free. CO2 selective membrane was superior in other aspects, namely higher CO2 purity, lower stage cut and feed pressure.

Understanding Single-Protein Fouling in Micro- and Ultrafiltration Systems via Machine-Learning-Based Models

Protein fouling is a complex mechanism. To enhance understanding on protein fouling of membranes, the target of this study is twofold: (i) to determine the relative influences of parameters via the Random Forest (RF) model and (ii) to evaluate the predictive capability of the Neural Network (NN) model. Membrane pore size is the most dominant influence on fouling followed by transmembrane pressure (TMP), while membrane configuration (i.e., flat-sheet, hollow fiber, or tubular) is the least dominant. The NN model gives modest predictive capability despite inconsistencies and variabilities of the experimental setups and protocols, which invariably affects the important parameters in the database compiled from past publications. The database was divided into microfiltration (MF) and ultrafiltration (UF) subsets based on the membrane pore size values. It was found that the dominant parameters for permeate flux are different, with membrane pore size and protein concentration being dominant for MF and UF, respectively, while TMP is dominant for protein rejection for both cases. For permeate flux, membrane material is the most dominant parameter for the non-BSA database, while membrane pore size remains the most dominant parameter for protein rejection regardless of the protein used. Results show that such data-driven RF and NN models can enhance the understanding on the relative dominance of the parameters on different phenomena and provide adequate prediction of protein fouling, in the absence of any governing equations.

Predictive modeling of single pass tangential flow filtration for continuous biomanufacturing.

Opportunities for process intensification have made continuous biomanufacturing an area of active research. While tangential flow filtration (TFF) is typically employed within the biologics purification train to increase drug substance concentration, single-pass TFF (SPTFF) modifies its format by enabling continuity of this process and achieving a multifold concentration factor through a single-pass over the filtration membranes. In continuous processes feed concentration and flow rate are determined by the preceding unit operations. Therefore, tight control of SPTFF output concentration must be achieved through precise design of the membrane configuration, unlike TFF. However, predictive modeling can be utilized to identify configurations that achieve a desired target concentration across ranges of possible feed conditions with minimal experimental data, hence enabling accelerated process development and design flexibility. We hereby describe the development of a mechanistic model predicting SPTFF performance across a wide design space using the well-established stagnant film model, which we demonstrate is more accurate at higher feed flow rates. The flux excursion dataset was generated within time constraints and with minimal material consumption, showing the method's ability to be quickly adapted. While this approach eliminates characterizing complex physicochemical model variables or the need for users with specialized training, the model and its assumptions become inaccurate at low flow rates, below 25 L/m2 /h, and high conversions, above 0.9. As this low flow rate, high conversion operating regime is relevant for continuous biomanufacturing, we explore the assumptions and challenges involved in predicting and modeling SPTFF processes, while suggesting added characterization to gain further process insight.

Functionalisation of Electrospun Cellulose Acetate Membranes with PEDOT and PPy for Electronic Controlled Drug Release.

Controlled drug release via electrical stimulation from drug-impregnated fibres was studied using electrospun cellulose acetate (CA) membranes and encapsulated ibuprofen (IBU). This research outlines the influence of polypyrrole (PPy) and poly(3,4-ethylenedioxythiophene) (PEDOT)-functionalised CA membranes and their suitability for dermal electronic-controlled drug release. Micro Raman analysis confirmed polymer functionalisation of CA membranes and drug incorporation. Scanning electron microscopy (SEM) images evidenced the presence of PPy and PEDOT coatings. The kinetic of drug release was analysed, and the passive and active release was compared. In the proposed systems, the drug release is controlled by very low electrical potentials. A potential of -0.3 V applied to membranes showed the ibuprofen retention, and a positive potential of +0.3 V, +0.5 V, or +0.8 V, depending on the conductive polymer and membrane configuration, enhanced the drug release. A small adhesive patch was constructed to validate this system for cutaneous application and verified an "ON/OFF" ibuprofen release pattern from membranes.

Fluid–structure coupled response of dynamical surfaces tailored in a flexible shell

The present study examines the fluid-coupled wave response of a stepped elastic membrane discontinuity connecting a flexible shell to the annular rigid shell. The acoustic radiation from the internal and annular regions propagates along the flexible boundaries as well as through the compressible fluid that fills the interior of the shell and scatters at geometric discontinuity and edges. In contrast to previous studies, an elastic membrane disc with different boundary conditions is considered as the geometric discontinuity rather than an acoustically rigid step-discontinuity in a cylindrical waveguide. The problem governed by the rigid step-discontinuity is solved using the mode matching technique, while the Galerkin procedure is used for the elastic membrane discontinuity. The truncated form of both solutions reconstructs the matching conditions and satisfies the conservation laws, which further authenticate the correctness of the solutions and the validity of the obtained numerical results based on these solutions. It is worth noting that the parametric configuration of the elastic membranes, the edge conditions and the radii of the shells have a significant impact on the attenuation of the noise control device.

Waste heat recovery enhancement in the CO2 chemical absorption process by hydrophobic-hydrophilic composite ceramic membranes

A novel ceramic composite membrane configuration was proposed to improve the waste heat recovery performance from stripped gas in the CO2 chemical absorption process. Tubular hydrophobic and hydrophilic ceramic membranes were serially assembled to form a single composite membrane. The stripped gas and bypassed CO2-rich solvent flowed countercurrent on both sides of the composite membrane. The waste heat recovery performance from the stripped gas was investigated under eight membrane configurations using: hydrophobic, hydrophilic, and Janus membranes (i.e., with hydrophilic inner-surface and hydrophobic outer-surface, and viceversa). Results showed that when the stripped gas enters the hydrophobic segment, the waste heat recovery performance increases to a plateau and then decreases with an increasing length of the hydrophobic segment. When the length ratio of the hydrophobic segment was 25%, a maximum waste heat recovery performance was achieved. Similarly, an increase in the hydrophobicity of the hydrophobic segment caused an increase in waste heat recovery performance, in which the optimal water contact angle (CA) was 137.35°. As a result of the abovementioned conditions, a 7.44%–25.15% higher waste heat recovery of the composite membrane was achieved compared to commercial hydrophilic membranes.

Evaluation of secondary effluent organic matter removal by an in-series forward osmosis-ultrafiltration hybrid process using parallel factor analysis with self-organizing maps

This study explores removal of effluent organic matter (EfOM) from secondary municipal wastewater effluent by a custom-devised in-series forward osmosis-ultrafiltration (FO-UF) hybrid system in which naturally-driven osmotic pressure, induced by the concentration difference between the feed solution and the draw solution, is a sole driving force for post UF filtration. Water flux and reverse salt flux are greatly affected by concentration and type of draw solution as well as different FO membrane configurations of the active layer facing feed solution (AL–FS) and the active layer facing draw solution (AL–DS). Maximum fluorescence intensity values obtained from parallel factor analysis (PARAFAC) revealed that the FO-UF hybrid process removes EfOM up to 97% of initial concentration over 2 h experimentation, owing to 6–8% of additional removal by post UF membrane. PARAFAC and self-organizing maps (SOM) modeling revealed that humic-like substances are removed preferentially over protein-like and smaller-sized organics in both AL–FS and AL–DS modes. However, in AL–DS mode, fouling, possibly due to humic-like substances, followed by deteriorating water quality, is observed earlier than in AL–FS mode. During the FO-UF processes, overall properties of EfOM in feed solution are shifted to hydrophilic and smaller-sized organic matter. This work provides a concept of pump-less FO-UF hybrid filtration and demonstrates the proposed system as a feasible option for EfOM removal in water reuse. As the first of its kind, the incorporation of PARAFAC with SOM modeling in FO process gives an insight into the fouling and transport of EfOM in the AL-FS and AL-DS modes.

Effect of flexible membrane in large-scale triaxial test DEM simulations

The use of flexible membrane boundaries in simulations of ballast triaxial tests with the discrete element method (DEM) has become increasingly popular, due to the benefits of more uniform confining pressure and realistic specimen deformation. However, it is not well understood whether the simulated flexible membranes may lead to overstated results due to extra confinement of the specimen. To investigate this, a series of three-dimensional (3D) discrete element simulations were performed using different flexible membrane configurations and parameters. The results showed that the flexible membrane has an effect on the stress-strain response of the specimen once axial strain exceeds 1%, and that a higher stiffness and larger element size of the membrane leads to greater extra confinement during shearing. A correlation model was developed to predict the extra confinement of the flexible membrane, which was validated to reasonably predict the restriction on triaxial test simulations.

Development of Solid-Contact Potentiometric Sensor Utilized Nanocarbon-filled Poly (vinyl chloride) Membrane as Ion-to-electron Transducing Layer

Current fundamental researches in the field of potentiometry demonstrate the perspectives of using polymeric nanostructured materials as ion-to-electron transducers in Solid-Contact Potentiometric Sensors (SCSs). This paper reports the preparation and comparative study of plasticized Poly(Vinyl Chloride) (PVC) membranes modified with fullerene C60, single-walled carbon nanotubes SWCNTs, multiwalled carbon nanotubes, and graphene oxide as the transducing layer in SCSs for the determination of a common local anesthetic drug – procaine hydrochloride (Pro·HCl). As an ion-sensitive (recognizing) layer, a PVC membrane containing highly lipophilic 2-[bis-octadecyl sulfo]-closo-decaborate anions was chosen. The results were discussed in relation to nanofiller’s type and content. The best potentiometric characteristics were obtained for the sensor with the transducing layer containing the hybrid nanofiller SWCNTs/C60. This new sensor of a double-layer PVC membrane configuration exhibited a Nernstian slope (59.2 ± 0.2 mV/decade) in the wide linear range (5×10-7– 1×10-2 M) with the low limit of detection (10-7.1 M), fast response time (≤ 7 s), and stable potentiometric response (drift potential ± 0.27 mV h-1 over 7 h of soaking in 1x10-5 M Pro·HCl solution).

Membrane-aerated biofilm reactor (MABR): recent advances and challenges

Abstract Membrane-aerated biofilm reactor (MABR) has been considered as an innovative technology to solve aeration issues in conventional bioreactors. MABR uses a membrane to supply oxygen to biofilm grown on the membrane surface. MABR can perform bubbleless aeration with high oxygen transfer rates, which can reduce energy requirements and expenses. In addition, a unique feature of counter-diffusion creates a stratified biofilm structure, allowing the simultaneous nitrification–denitrification process to take place in a single MABR. Controlling the biofilm is crucial in MABR operation, since its thickness significantly affects MABR performance. Several approaches have been proposed to control biofilm growth, such as increasing shear stress, adding chemical agents (e.g., surfactant), using biological predators to suppress microorganism growth, and introducing ultrasound cavitation to detach biofilm. Several studies also showed the important role of membrane properties and configuration in biofilm development. In addition, MABR demonstrates high removal rates of pollutants in various wastewater treatments, including in full-scale plants. This review presents the basic principles of MABR and the effect of operational conditions on its performance. Biofilm formation, methods to control its thickness, and membrane materials are also discussed. In addition, MABR performance in various applications, full-scale MBRs, and challenges is summarized.

Molecular dynamics study of the influence of cholesterol on the rigidity of an asymmetric membrane of red blood cells.

Analysis of the mechanical properties of the plasma membrane of red blood cell (RBC) is useful for the future exploration of cell-targeted methods for treatment of Alzheimer's disease. This preliminary study aimed to observe the effects cholesterol and lipid concentration/asymmetry have on the membrane rigidity and bilayer thickness. We focused on the structure-property relationship in the plasma membranes via the analysis of bending rigidity as a function of the molar concentration of the cholesterol and lipids in the plasma membrane. The plasma membrane of RBC consists mainly of cholesterol, phosphatidylcholine (PC), sphingomyelin (SM), and proteins. Cholesterol plays a key role in the plasma membrane by maintaining its viscoelasticity and structure via modulating the fluidity and rigidity of the membrane. To analyze these properties, the coarse-grained (CG) molecular dynamics (MD) simulations were performed. The membrane building included cholesterol molar concentration ranging from 10% to 30%. To replicate the asymmetry of the cell SM and PC, the molar concentrations of lipids were varied in the range of 10%-20% and 50%-80%, respectively. The initial membrane configuration was generated using CHARMM-GUI (online graphical user interface tool). The MD simulations were performed with the Gromacs (molecular dynamic simulation program) software using all-atom and coarse-grained approaches. The aggregation of cholesterol at various molar concentrations was observed along with the fluctuation of rigidity, which could be tentatively attributed to the lipid types used in the study, the ratio of cholesterol and lipids, and the use of water as a solvent for both the inner and outer leaflet. In the future we will focus on the all-atom study of the tail interactions between cholesterol and lipids in order to identify the leading factors contributing to the bending rigidity.

Identify some virulence factors of bacteria Proteus mirabilis isolated from people with otitis

This study was carried out during the period from 5/4/ to 13/11/2016, collected (50) then swab from patients with acute and chronic otitis reviewers to Advisory clinic ear nose and throat Division at Baquba General Hospital, The aim of this current study was to isolate and diagnose proteus mirabilis and detection of some of its virulence factors. Smear incubated culture media and diffrentation, and then subjected to microscopic, biochemical tests germ farms for the purpose of diagnosing the variable spores. Test investigation of dynamic membrane configuration outside the living body run by using the variable germ isolated Congo-red dye. 10 (20%) (streak of Proteus mirabilis, type either wipes which showed the volatile race not pathogen growth was 30, (60 %), while negative smears for bacterial 10 (20%) .The results of a study showed virulence factors of bacteria the variable to 10 (100 %) isolation of her ability to produce swarming movement, 9 (90%) isolation possesses the ability to analyses human red blood cells, while 9 (90%) isolation of dynamic membrane configuration capability

Pervaporation Membrane-Catalytic Reactors for Isoamyl Acetate Production

This study reports the analysis and design of a liquid phase esterification process to convert acetic acid with isoamyl alcohol into isoamyl acetate via reactive pervaporation, in the presence of an Amberlite IR-120 ion exchange resin catalyst. To accomplish this, a catalytic reactor is coupled with a separation membrane unit (Pervaporation Membrane Reactor (PVMR)). In the proposed unit, the chemical reaction equilibrium is favorably shifted towards isoamyl acetate formation by removing water with the help of a separation membrane. The study is developed by using relevant thermodynamics, kinetics, and membrane transport models, and by considering different catalytic reactor-pervaporator membrane configurations such as: (a) a two-step continuous fixed bed-pervaporator process (FBR+PVMU), (b) a two-step continuous slurry reactor-pervaporator process (SR+PVMU), (c) a single-step integrated fixed bed-pervaporator reactor (IFBPVMR), and d) a single step integrated slurry-pervaporator reactor (ISPVMR). The performance of the PVMRs is evaluated by using a R recycle ratio, a Ω membrane area to reactor volume ratio, and Da Damköhler dimensionless parameters. From the various proposed configurations, it is shown that the integrated plug flow reactor-pervaporation reactor (IFBPVMR) provides the best performance. On the basis of various simulations and design charts developed in the present study, operational conditions leading to optimum ester yields as high as 0.94 are predicted. These results provide a valuable prospect for the industrial scale-up and implementation of isoamyl acetate production units.

Toward Redox-Free Reverse Electrodialysis with Carbon-Based Slurry Electrodes.

Clean and renewable salinity gradient energy can be harvested using reverse electrodialysis (RED). The electrode system is an essential part to convert ionic current into electrical current. In this study, a typical 0.10 × 0.10 m2 RED stack with a cross-flow configuration was used to test carbon-based slurry electrodes (CSEs) to replace the usual redox solutions, like hexacyanoferrate, to enhance the RED process' sustainability, stability, and economic value. Six different slurry compositions comprising activated carbon, carbon black, and graphite powder were tested. The CSE characteristics were systematically studied by measuring viscosity, electrode compartment pressure drop, maximum current density, stability, and performance of power density and energy efficiency. Using a single membrane configuration, the CSE ran continuously for 17 days with a stable output. The application of CSEs for RED, with artificial seawater and river water, using mixing activated carbon and carbon black at a total concentration of 20 wt %, resulted in the best performance with a net power density of 0.7 W·m-2. Moreover, higher current densities up to 350 A·m-2 were tested for ED and shown to be feasible until 150 A·m-2. CSEs show promising versatility for different application modes.

Cellulose acetate-TiO2 and activated carbon electrospun composite fibre membranes for toluene removal

The VOCs removal from polluted air has been achieved using several different methods but primarily through the use of adsorbent materials or through degradation with photocatalytic oxidation (PCO). Fibres produced by electrospinning have the possibility to easily incorporate additives into the fibres and onto their surface. This can functionalise them for efficient VOCs removal. Cellulose acetate (CA)-based electrospun fibre membranes have been fabricated and doped with activated charcoal (AC) and titanium dioxide (TiO2), either separately or in combination to investigate their toluene removal capacity of the single additive and the synergic effects of adsorption and PCO. Two different methods of functionalisation of the fibres with AC and TiO2 have been used. These methods are air spraying and electro-spraying. Several configurations of the final membranes have been investigated. SEM images indicate that the additives have been successfully distributed on the fibre surface and they affect their morphology by increasing the overall roughness and the thickness of the final membranes. Adsorption with AC achieved 45.5% removal of toluene with a starting concentration of 22.5 ppm. PCO was probably initiated using a blacklight blue UV lamp with a peak wavelength of 365 nm as formation of formaldehyde was recorded. The findings suggest that PCO is affected by the residence time and UV light intensity.

Role of electrode and proton exchange membrane configurations on microbial fuel cell performance toward bioelectricity generation integrated wastewater treatment

In the present study, the effects of electrode surface area, proton exchange membrane area, and volume of the anodic chamber were investigated on the performance of five different dual chamber microbial fuel cells (MFC) using synthetic wastewater toward wastewater treatment coupled electricity generation. In the batch mode, the five different MFC's were operated with the anodic chamber volumes of 93–890 mL, 17.33–56.77 cm2 electrode surface area, obtained volumetric power densities of 137.72–58.13 mW/m3, and unit area power densities ranging from 27.04 to 11.94 mW/m2. Fed-batch studies were done with the MFC having 740 mL anodic chamber volume at different wastewater COD concentrations. The power density per unit area increased from 22.93 mW/m2 to 36.25 cm2 when the distance between electrodes was reduced from 10 to 6 cm. A maximum volumetric power density of 135.21 mW/m3 has been attained with a 6 cm electrode distance with the accomplished COD reduction of 93.21%. The presence of biofilm on the anode has been visualized through the SEM images. The higher COD concentration of wastewater and the fed-batch operation resulted in increased power output and wastewater treatment efficiency.

Both sides matter: anode configurations alter the activity of electrolyzers for organic hydrogenations

The compression between the electrodes, choice of the anode transport layer, membrane and MEA configuration, all strongly interplay with each other, influencing both electrocatalytic activity and selectivity of the cathodic hydrogenation reaction.

An integrated MDC-FO membrane configuration for simultaneous desalination, wastewater treatment and energy recovery.

A novel microbial desalination cell (MDC) configuration was developed by introducing a forward osmosis (FO) membrane, separating the cathode chamber from a fourth extra chamber. Wastewater is treated using a sequential anode-cathode feed. The new chamber then serves as a FO draw chamber, where a saline solution is used to recover freshwater from the adjacent cathode chamber. The diluted saline solution then goes to the MDC middle chamber for further desalination. Three identical cells were constructed and operated in cyclic-batch-flow mode at different initial wastewater and saline solution concentrations. Up to 84.8 ± 1.7% of the wastewater was recovered as freshwater. Freshwater recovery decreases at lower salt concentrations and higher wastewater COD concentrations due to the lower osmotic pressure difference. Salinity of saline water was decreased by up to 69.57 ± 3.85% at the highest initial salinity. COD removal up to 94.42 ± 4.15% was reached. COD removal rates were higher at higher COD concentrations. Polarization curves show the effect of COD on the internal resistance, where cells operated at lower COD experienced higher internal resistance. Scanning electron microscopy (SEM) images revealed the extent of fouling on the ion exchange membrane and biofilm formation on the FO membranes and the electrodes.