Membrane Separation Processes Research Articles

Donnan Dialysis for Recovering Ammonium from Fermentation Solutions Rich in Volatile Fatty Acids.

For the production of polyhydroxyalkanoates (PHA) using nitrogen-rich feedstocks (e.g., protein-rich resources), the typical strategy of restricting cell growth as a means to enhance overall PHA productivity by nitrogen limitation is not applicable. In this case, a possible alternative to remove the nitrogen excess (NH4+/NH3) is by applying membrane separation processes. In the present study, the use of Donnan dialysis to separate ammonium ions from volatile fatty acids present in the media for the production of PHA was evaluated. Synthetic and real feed solutions were used, applying NaCl and HCl receiver solutions separated by commercial cation-exchange membranes. For this specific purpose, Fumasep and Ralex membranes showed better performance than Ionsep. Sorption of ammonium ions occurred in the Ralex membrane, thus intensifying the ammonium extraction. The separation performances with NaCl and HCl as receiver solutions were similar, despite sorption occurring in the Ralex membrane more intensely in the presence of NaCl. Higher volumetric flow rates, NaCl receiver concentrations, and volume ratios of feed:receiver solutions enhanced the degree of ammonium recovery. The application of an external electric potential difference to the two-compartment system did not significantly enhance the rate of ammonium appearance in the receiver solution. The results obtained using a real ammonium-containing solution after fermentation of cheese whey showed that Donnan dialysis can be successfully applied for ammonium recovery from such solutions.

Tangential microfiltration of lime and pineapple juices using inexpensive tubular ceramic membrane and analysis of fouling mechanism

A non-thermal tangential filtration of lime and pineapple juices using an indigenously elaborated inexpensive bentonite-based tubular ceramic membrane (96 $/m2) is discussed in the present work. The fabricated membrane exhibited a porosity of 37% with 0.11 µm pore size and possessed adequate flexural stability of 18 MPa. Microfiltration experiments were conducted for both centrifuged juice (CJ) and Enzymatic treated centrifuged juice (ETCJ) of lime and pineapple at various operating pressures (69 – 345 kPa) and crossflow rates (110 – 150 Lph) to evaluate their effects on the resulting permeate flux and clarified juice properties. The membrane provided a maximum permeate flux of both ETCJ of lime and pineapple juices as 2.22 × 10−5 m3/m2s and 1.31 × 10−5 m3/m2s, respectively, at operating conditions of 345 kPa pressure and 150 Lph flowrate. Enzymatic pretreatment considerably enhanced the permeate fluxes of both juices. Also, comparatively a high clarity and complete removal of alcohol-insoluble solids were observed for permeate streams of ETCJ. In all the cases, the desirable characteristics of citrus juices, including pH, total soluble solids, and citric acid content, were unaltered, ensuring the uniqueness of the membrane separation processes. Furthermore, fouling analysis was carried out using Hermia's models, revealing experimental data best fits into the cake filtration model for pineapple juice and intermediate pore blocking model for lime juice clarification are identified as dominant mechanisms, respectively.

Optimal dispatch of HCNG penetrated integrated energy system based on modelling of HCNG process

Hydrogen is injected into the existing natural gas network to form hydrogen-rich compressed natural gas (HCNG), effectively addressing the high cost of hydrogen transmission. However, the traditional IES model cannot be used due to the hydrogen injection's effect on gas properties and the vague characteristics of the transport and separation processes. Therefore, this paper proposes an HCNG penetrated integrated energy system (HPIES) optimal dispatching method by comprehensively modelling the injection, transmission, and separation processes of HCNG. An HCNG mass flow rate model considering variable mixing ratio and unknown beginning flow direction is developed to describe the effect of hydrogen injection. Furthermore, the hydrogen separation model is established by introducing a combined membrane and pressure swing adsorption separation process. The tightening McCormick algorithm is proposed to solve quickly HPIES optimal dispatch problem with an acceptable feasibility check. Finally, case studies on the HPIES consisting of IEEE 39-bus power system and 20-node natural gas system validate the effectiveness of the algorithm and model. The results show that the average error is 0.031% for the bilinear term constraint.

Computational simulation of molecular separation in liquid phase using membrane systems: Combination of computational fluid dynamics and machine learning

A new methodology was developed in this work based on combination of machine learning and computational fluid dynamics (CFD) for hybrid modeling of membrane separation processes. The developed methodology was tested for a separation case in removing organic molecules from aqueous solution using a polymeric membrane in cylindrical shape. The CFD simulation was carried out via finite element technique. The results of the CFD outputs were inputted several machine learning techniques to build the hybrid model of the process. The data of mass transfer in form of concentration was extracted which are more than 2000 data points. The dataset includes two inputs r and z, in addition to one output (C). A number of different models are selected for this purpose, including Random Forests, Gradient Boosting models and Extremely Randomized Trees (Extra Trees). During the course of this research, it was confirmed that these models are capable of performing very well in this dataset when their hyper-parameters are optimally chosen. The R2 parameter for all three methods was higher than 0.99, indicating that the performance was very favorable. It is noteworthy that the RMSE metric decreased to 2.43 and the MAE metric has also decreased to 1.06 by optimization.

Membrane Technology as a Strategy for Improving β-Galactosidase Concentration Processes: The Influence of the pH, Membrane Molecular Weight, Pressure, and Ionic Strength in the Process

The enzyme β-galactosidase catalyzes the hydrolysis of lactose into glucose and galactose, although for its effective application it is necessary to establish techniques for purification, concentration, or polishing, such as membrane separation processes, in particular ultrafiltration. The present study aimed to investigate ultrafiltration and diafiltration applied as initial steps for concentration and salt removal, respectively, in the β-galactosidase purification processes. Additionally, the influence levels of the pH (6.5, 7.7, or 7.5), membrane molecular weight cut-off (30, 50, 60, or 100 kDa), operating pressure (1.5, 2.0, or 2.5 kgf/cm2), and ionic strength of the ultrafiltration using NaCL or KCl (0.01–0.1 M) were evaluated considering the enzyme recovery, purification, retention, and concentration factors in relation to the proteins, volume, activity, and protein flux and yield of the processes. The ultrafiltration of the crude enzyme extract at pH 7.5 and 1.5 kgf/cm2 with a 50 kDa polyethersulfone membrane resulted in a volume concentration of the β-galactosidase extract up to 7.1-fold greater, a purification factor 1.2-fold greater, and an enzyme recovery rate of 108.9% by eliminating metabolites during the purification process. In addition, the lowest flux variation range (16.0 to 13.1 L/m2·h) was observed under these same conditions, thereby representing a decrease of 18.0%. An increase in the operating pressure and the addition of salts results in reduced enzyme recovery (up to 38% of the process yield (734.1 to 453.7 U/h) and up to 40% of the enzyme recovery rate (108.9 to 60.6%) during the ultrafiltration using NaCl, respectively). The operation in the diafiltration mode allowed salt removal after the purification of β-galactosidase (enzymatic recovery rates above 93.4%) via precipitation and ion-exchange chromatography elution and as part of an aqueous two-phase system using 6 diafiltration cycles, thereby revealing its application potential.

Cobalt oxide functionalized ceramic membrane for 4-hydroxybenzoic acid degradation via peroxymonosulfate activation

Membrane separation and sulfate radicals-based advanced oxidation processes (SR-AOPs) can be combined as an efficient technique for the elimination of organic pollutants. The immobilization of metal oxide catalysts on ceramic membranes can enrich the membrane separation technology with catalytic oxidation avoiding recovering suspended catalysts. Herein, nanostructured Co3O4 ceramic catalytic membranes with different Co loadings were fabricated via a simple ball-milling and calcination process. Uniform distribution of Co3O4 nanoparticles in the membrane provided sufficient active sites for catalytic oxidation of 4-hydroxybenzoic acid (HBA). Mechanistic studies were conducted to determine the reactive radicals and showed that both SO4•− and •OH were present in the catalytic process while SO4•− plays the dominant role. The anti-fouling performance of the composite Co@Al2O3 membranes was also evaluated, showing that a great flux recovery was achieved with the addition of PMS for the fouling caused by humic acid (HA).

Multi-scale design of MOF-based membrane separation for CO2/CH4 mixture via integration of molecular simulation, machine learning and process modeling and simulation

Metal-organic framework (MOF) membranes have demonstrated high efficiency for CO2 capture due to their wide range of pore sizes, high surface area, high porosity, and open metal sites. In this work, we propose a multi-scale design framework of MOF-based membrane separation for CO2/CH4 mixture via integration of molecular simulation, machine learning, and process modelling and simulation. The GCMC and MD molecular simulation is first used to evaluate adsorption isotherms, isosteric adsorption heat, self-diffusivity, activation energy, permeability, and selectivity of a MOF-based membrane (e.g., IRMOF-1) for CO2/CH4 separation at different operating conditions. It is found that the simulated isotherms at 298 K are consistent with experimental results. CO2 permeability can range from 4.090 × 104 to 3.818 × 105 barrer with variation in operating conditions. The same phenomenon is also reflected in the selectivity. We then establish prediction models of adsorption capacity and self-diffusivity using machine learning methods such as artificial neural network (ANN), which are used to calculate the permeability. The mean squared error is 0.0086, and the coefficient of determination is 0.9822. The proposed ANN models are integrated with the tanks-in-series model of a hollow fiber membrane separation process, which is simulated using the finite volume method. Three case studies illustrate the feasibility and superiority of the proposed integrated framework.

Magnetic confinement-enabled membrane reactor for enhanced removal of wide-spectrum contaminants in water: Proof of concept, synergistic decontamination mechanisms, and sustained treatment performance

Membrane chemical reactors (MCRs) have demonstrated a great potential for simultaneous removal of wide-spectrum pollutants in advanced water treatment. However, current catalyst (re)loading and catalytic reactivity limitations obstruct their practical applications. Herein, as a proof-of-concept, we report a hollow fiber membrane chemical reactor (HF-MCR) with high and sustainable catalytic reactivity, enabled by novel magnetic confinement engineering of the catalysts. Namely, the zerovalent iron (ZVI) nanocatalysts were spatially dispersed and confined to nearly parallel magnetic induction lines, forming forest-like microwire arrays in the membrane lumen. Such arrays exhibited ultrahigh hydrodynamic stability. The HF-MCR integrated sequential membrane separation and Fenton-like catalysis, thus being capable of high and synergistic wide-spectrum decontamination. The membrane separation process completely removed large nanoplastics (NPs) via size exclusion, and thus the subsequent Fenton-like catalysis process enhanced removal efficiency of otherwise permeated bisphenol A (BPA) and phosphate (P) by in situ generated reactive oxygen species (primarily 1O2) and iron (oxyhydr)oxides, respectively. Furthermore, highly dispersed ZVI arrays and their continuous surface depassivation driven by magnetic gradient and hydrodynamic forces conferred abundant accessible catalytic sites (i.e., Fe0 and FeII) to stimulate Fenton-like catalysis. The consequent enhancement of BPA and P removal kinetics was 3–765 and 49–492 folds those in conventional (flow-through or batch) systems, respectively. Periodic ZVI reloading ensured sustained decontamination performance of the HF-MCR. This is the first demonstration of the magnetic confinement engineering that enables efficient and unlimited catalyst (re)loading and sustainable catalytic reactivity in the MCR for water treatment, which is beyond the reach of current approaches.

Reduction of Ultrafiltration Membrane Fouling by the Pretreatment Removal of Emerging Pollutants: A Review.

Ultrafiltration (UF) processes exhibit high removal efficiencies for suspended solids and organic macromolecules, while UF membrane fouling is the biggest obstacle affecting the wide application of UF technology. To solve this problem, various pretreatment measures, including coagulation, adsorption, and advanced oxidation, for application prior to UF processes have been proposed and applied in actual water treatment processes. Previously, researchers mainly focused on the contribution of natural macromolecular pollutants to UF membrane fouling, while the mechanisms of the influence of emerging pollutants (EPs) in UF processes (such as antibiotics, microplastics, antibiotic resistance genes, etc.) on membrane fouling still need to be determined. This review introduces the removal efficiency and separation mechanism for EPs for pretreatments combined with UF membrane separation technology and evaluates the degree of membrane fouling based on the UF membrane's materials/pores and the structural characteristics of the cake layer. This paper shows that the current membrane separation process should be actively developed with the aim of overcoming specific problems in order to meet the technical requirements for the efficient separation of EPs.

Preliminary study on ZIF-8 containing hollow fiber mixed matrix membranes (HFMMMs) for CO2 and CH4 gas permeation

The advantages in terms of smaller footprint, higher energy efficiency, larger surface-to-volume ratio and higher flux have opened various opportunities for hollow fiber membranes in separation processes especially in carbon dioxide (CO2) capture. Although the development of polymeric hollow fiber membrane has emerged as an important material in membrane technology, currently existing polymeric materials suffer from a limiting trade-off between selectivity and permeability. Recently, it has been reported in the literature that the addition of metal–organic frameworks into polymer matrixes have radically improved the separation performance of CO2 from methane (CH4), as well as enhanced the thermal stability and structural properties of the membrane. In this preliminary study, ZIF-8/cellulose triacetate hollow fiber mixed matrix membranes are fabricated by varying the air gap distances and subsequently, the morphology of the resultant membranes was analysed using a scanning electron microscope while the dispersion of ZIF-8 fillers in the polymer matrix was observed using an energy dispersive X-ray. The results showed that the ZIF-8 fillers were homogeneously distributed into the cellulose triacetate polymer. Then, the performance of the resultant membranes before and after post-treatment with polydimethylsiloxane in CO2 and CH4 gases permeation were evaluated. Due to the presence of multiple defects, the overall performance of the fabricated membranes was low with no significant improvements after post-treatment. Hence, further optimization study on the fabrication process is still required to improve the performance of the ZIF-8/cellulose triacetate hollow fiber mixed matrix membrane in CO2 and CH4 gas permeation.

Incorporation of porous materials in forward osmosis membrane for increased water recovery from waste streams

Forward osmosis (FO) is a membrane separation process that involves an osmotic pressure-driven, semi-permeable membrane to selectively separate water from waste streams. Increased water flux and salt removal characterize an ideal FO membrane. In contrast to the first-developed symmetric cellulose triacetate (CTA) membrane, the thin film composite (TFC) membrane had a higher water flow and a lower reverse salt flux. The incorporation of porous and non-porous nano-sized particles in the membrane structure has improved TFC performance even further. The TFC-FO membrane was created in this study by incorporating porous ZIF-8 MOF into the polyethersulphone (PES) support layer. Interfacial polymerization of chitosan (CS) biopolymer and trimesoyl chloride (TMC) produced the thin separation layer. The porous MOFs provided additional water pathways. The water wettability of the separation layer was also improved by CS-TMC polymerization. In comparison to the bare membrane, the water fluxes of the ZIF-8@FO membrane improved by 2.8 times. The newly developed FO membrane was found effective for use in sewage and wastewater treatment.

Construction of membrane reactors coupled with conjugated network hollow microspheres for cascade production of block copolymers

We present a design for cascade polymer production by exploiting the construction of membrane reactors coupling with conjugated network hollow microspheres as suspended catalysts to combine aqueous photopolymerization and membrane separation process.

Application of UV-VIS-NIR spectroscopy in membrane separation processes for fast quantitative compositional analysis: A case study of egg products

Membrane separation technology is achieving broad applications in research, food and pharmaceutical industry. In this study, the application of UV-VIS-NIR spectroscopy to quantify the composition of the fractions obtained in a membrane separation process was assessed. An egg membrane filtration was employed as a case study to develop predictive models for a rapid determination of dry matter, protein and cholesterol composition in the feed and the fractions (retentate and filtrate). Whole egg plasma and egg yolk plasma obtained by centrifugation, and egg white were tangential filtrated using different pore size and membrane materials. Transmittance UV-VIS-NIR spectra showed significant differences between samples. Cholesterol, dry matter and proteins were predicted with UV-VIS-NIR spectroscopy with good statistical significance (RPDEV over 3). UV-VIS-NIR spectroscopy combined with chemometric tools demonstrates to be an efficient green method for composition analysis in the membrane filtration process. It is reliable, non-destructive, quick and environmentally friendly. Moreover, it can be applied on-line for real-time quantitative compositional analysis.

Properties of concentrated skim rubber latex using membrane separation process and its comparison with other natural rubber latexes

Properties of concentrated skim rubber latex using membrane separation process and its comparison with other natural rubber latexes

State-of-the-Art of Polymer/Fullerene C60 Nanocomposite Membranes for Water Treatment: Conceptions, Structural Diversity and Topographies.

To secure existing water resources is one of the imposing challenges to attain sustainability and ecofriendly world. Subsequently, several advanced technologies have been developed for water treatment. The most successful methodology considered so far is the development of water filtration membranes for desalination, ion permeation, and microbes handling. Various types of membranes have been industrialized including nanofiltration, microfiltration, reverse osmosis, and ultrafiltration membranes. Among polymeric nanocomposites, nanocarbon (fullerene, graphene, and carbon nanotubes)-reinforced nanomaterials have gained research attention owing to notable properties/applications. Here, fullerene has gained important stance amid carbonaceous nanofillers due to zero dimensionality, high surface areas, and exceptional physical properties such as optical, electrical, thermal, mechanical, and other characteristics. Accordingly, a very important application of polymer/fullerene C60 nanocomposites has been observed in the membrane sector. This review is basically focused on talented applications of polymer/fullerene nanocomposite membranes in water treatment. The polymer/fullerene nanostructures bring about numerous revolutions in the field of high-performance membranes because of better permeation, water flux, selectivity, and separation performance. The purpose of this pioneering review is to highlight and summarize current advances in the field of water purification/treatment using polymer and fullerene-based nanocomposite membranes. Particular emphasis is placed on the development of fullerene embedded into a variety of polymer membranes (Nafion, polysulfone, polyamide, polystyrene, etc.) and effects on the enhanced properties and performance of the resulting water treatment membranes. Polymer/fullerene nanocomposite membranes have been developed using solution casting, phase inversion, electrospinning, solid phase synthesis, and other facile methods. The structural diversity of polymer/fullerene nanocomposites facilitates membrane separation processes, especially for valuable or toxic metal ions, salts, and microorganisms. Current challenges and opportunities for future research have also been discussed. Future research on these innovative membrane materials may overwhelm design and performance-related challenging factors.

A Review on the Morphology and Material Properties of the Gas Separation Membrane: Molecular Simulation.

Gas membrane separation technology is widely applied in different industry processes because of its advantages relating to separation performance and economic efficiency. It is usually difficult and time consuming to determine the suitable membrane materials for specific industrial separation processes through traditional experimental research methods. Molecular simulation is widely used to investigate the microscopic morphology and macroscopic properties of materials, and it guides the improvement of membrane materials. This paper comprehensively reviews the molecular-level exploration of the dominant mechanism and influencing factors of gas membrane-based separation. The thermodynamics and kinetics of polymer membrane synthesis, the molecular interactions among the penetrated gases, the relationships between the membrane properties and the transport characteristics of different gases in the composite membrane are summarized and discussed. The limitations and perspectives of the molecular simulation method in the study of the gas membrane separation process are also presented to rationalize its potential and innovative applications. This review provides a more comprehensive reference for promoting the materials' design and engineering application of the gas separation membrane.

Revealing key meso-particles responsible for irreversible membrane fouling in an integrated oxidation-coagulation ultrafiltration system: Fouling behavior and interfacial interaction mechanism

This study applied a ferrate in-situ oxidation-coagulation ultrafiltration integrated system in drinking water treatment, illustrating the influence of meso-particles on membrane fouling behavior by oxidation-coagulation regulating. Under neutral conditions, the meso-particles between 20 and 100 nm were the mainly components at initial oxidation phase. Subsequently small molecules gathered to meso-particles of 200–500 nm under the flocculation, and 40 % of micro-particles aggregates were detected finally. According to the statistical correlation between multiscale particles and membrane flux and resistance, wherein meso-particle especially in range of 20–100 nm principally contributed to the irreversible fouling while the correlation coefficients above 0.9, and reversible fouling related to the synergy of meso- and micro-particles. Additionally, the fouling behavior of meso-particles on the membrane surface and the structural evolution of the fouling layer were illustrated based on the interfacial interaction, UV–vis reflectance spectroscopy and molecular dynamics simulation. The changes in hydrophilicity and charge of the meso-particle (20–100 nm) increased the attractive interaction with the membrane, causing severe membrane fouling. As flocculation progressed, the polynuclear Fe-hydroxide interacted with HA molecular fragments, and aggregated to meso-particles in range of 200–500 nm, which had smaller molecular gap and more tight structure than micro-particle (500–1000 nm), due to the HA molecular fragments were more strongly bound on the polynuclear Fe-hydroxide compared to iron hydroxide cluster. The stable and compact structure induced the meso-particles deposited on membrane surface and hardly be physically cleaned. The investigation of meso-particle on membrane fouling was provided new insight into the membrane separation process.

Improvement of permeability and antifouling performance of PVDF membranes via dopamine-assisted deposition of zwitterionic copolymer

Hydration is critical to restricting surface fouling in membrane separation processes. In order to tightly coat hydrophobic membrane surfaces with zwitterions that afford excellent hydration ability, herein, a facile strategy combining copolymer design and dopamine-assisted co-deposition was described. Three copolymers containing dopamine methacrylamide (DMA) unit and 2-methacryloyloxyethyl phosphorylcholine (MPC) unit, with/without a third hydrophilic unit, were synthesized via free radical polymerization, and characterized by 1H nuclear magnetic resonance (1H NMR) spectroscopy, Fourier-transform infrared (FTIR) spectroscopy and gel-permeation chromatography (GPC). Subsequently, the as-synthesized copolymers were co-deposited with dopamine hydrochloride on polyvinylidene fluoride (PVDF) membrane surfaces. X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), atomic force microscopy (AFM) and water contact angle (WCA) measurements were conducted to analyze the superficial chemical composition, morphologies, roughness and hydrophilicity of the membranes. Systematical filtration and antifouling experimental investigations showed that the zwitterionic-copolymer-modified membranes demonstrated high permeate fluxes, good rejection performance, and great antifouling properties, attributing to the enhanced hydrophilicity of the membrane surfaces. Especially, the p(DM)/PDA-PVDF modified membrane exhibited outstanding water flux of 192.5 L·m−2·h−1 and ideal BSA rejection of 96.1 % with excellent flux recover ratio (FRR1: 82.6 %, FRR3: 97.8 %). This work presents a feasible hydrophilic modification strategy of hydrophobic membranes, which is expected to provide a new avenue to overcome the permeability-selectivity trade-off limitations and fouling problems in membrane separation processes.

Extra A Review of Nanofiltration Membrane Technology To Treat Water Problems

One of the most widely used membranes is the nanofiltration membrane, this membrane is formed from various nanomaterials, such as metal nanoparticles and metal oxides, carbon-based nanoparticles, metal organic frameworks, and micro or organic nanoparticles. Membrane separation processes are used to concentrate or fractionate liquids to produce two liquids with different compositions. This makes the nanofiltration process an alternative compared to conventional processes. The potential of nanofiltration membranes can be used in textile industry wastewater treatment, tofu liquid waste, tofu liquid waste treatment, batik wastewater testing, and groundwater management as drinking water. In addition, nanofiltration membrane technology can be used as a separator for a substance in the air, such as removal of cypermethrin, arsenic cream, concentration of lactic acid bacteria as a tasty probiotic, removal of carbosulfan, Zr-Hf separation, and can see the characterization and performance evaluation of the antifouling properties of membranes. . Based on the process, the performance of a membrane is determined by two simple factors, namely flux (permeate flow rate) and membrane selectivity.

Hydroxytyrosol Enrichment of Olive Leaf Extracts via Membrane Separation Processes.

Antioxidants isolated from plant materials, such as phenolics, have attracted a lot of attention because of their potential uses. This contributes to the idea of the biorefinery, which is a way to produce useful products from biomass waste. Olea europaea byproducts have been extensively investigated for their large contents in phenolics. Oleuropein is a phenolic compound abundant in olive leaves, with its molecule containing hydroxytyrosol, elenolic acid, and glucose. In this work, olive leaf extracts were treated using different combinations of ultrafiltration and nanofiltration membranes to assess their capacity of facilitating the production of hydroxytyrosol-enriched solutions, either by separating the initially extracted oleuropein or by separating the hydroxytyrosol produced after a hydrolysis step. The best performance was observed when an ultrafiltration membrane (UP010, 10,000 Da) was followed by a nanofiltration membrane (TS40, 200-300 Da) for the treatment of the hydrolyzed extract, increasing the purity of the final product from 25% w/w of the total extracted compounds being hydroxytyrosol when membrane processes were not used to 68% w/w.