Recycle Membrane Research Articles

Green ammonia production via recycle membrane reactor: Experiment and process simulation

With the increasing demand for ammonia (NH3) and the environmental benefits, green and sustainable NH3 production has been urgently developed and is expected to replace the traditional Haber-Bosch (HB) process with high energy consumption and COx emission. In this work, a recycle membrane reactor (RMR) process where a catalytic reactor relates to a membrane separator in series and the retentate stream is recycled to the reactor was designed and executed to produce NH3, in which a Ru (10 wt%)/Cs/MgO catalyst and two membranes with different permeation properties and NH3 selectivity were used. By independently controlling the temperature of the reactor and membrane separator, the synthesized NH3 was selectively extracted from feed side to permeate side by Aquivion/ceramic composite and sulfonated (3-mercaptopropyl)trimethoxysilane membranes. Impressively, NH3 mole fraction was greatly increased from 0.01 of equilibrium state to 0.1–0.45 in permeate stream, which is ascribed to the permeation properties and NH3 selectivity of membrane at different temperatures. Moreover, a one-dimensional, isothermal, and plug-flow model was proposed to simulate RMR, which can be successfully applied to deeply understand the mechanism of RMR. Furthermore, a green NH3 production process based on RMR was simulated to give rationalized suggestions for the NH3 synthesis under mild conditions.

Recycling of PFSA-Based Membranes and Their Re-Application in PEM Fuel Cells

The commercialization of PEM fuel cells offers a promising opportunity to overcome our dependence on fossil fuels and provides an attractive alternative for automotive and stationary power applications.[1] However, PEMFCs are still costly in production, with the main cost factor due to the fabrication of the perfluorosulfonic acid (PFSA)-based proton exchange membrane and the noble metal catalysts.[2,3] Recycling of these components could increase the economic attractiveness of PEMFCs. However, while the high resistance of the ionomer membrane to thermal and chemical degradation is favorable for their use in fuel cells, it also makes membrane recycling a major challenge.Here, we present a newly developed recycling strategy to recover PFSA-based membranes after operation by a hydrothermal treatment. Both short side chain (SSC) and long side chain (LSC) ionomers with EWs of 800 and 1000 were investigated. In contrast to previously published methods, we were able to recover the PFSA ionomer by using water instead of high-boiling organic solvents, such as DMF or DMSO.[4,5] The recycled membranes were obtained from the recycled PFSA ionomer solution by doctor-blading. They were investigated by in-situ Raman techniques for studying the water uptake and analyzed by IR and small-angle X-ray scattering (SAXS) techniques to get a more detailed insight into their morphology. In single cell tests at standard (80 °C) and enhanced (up to 130 °C) PEMFC operating temperatures, the recycled membranes showed an increased cell performance as compared to the pristine 3M-800EW membrane. Solid-state NMR measurements confirmed that no chemical changes in the membrane occurred due to the heat-treatment process.We assume that the observed performance boost can be attributed to an increased water uptake and retention. Furthermore, a change in the polymer matrix formation may be responsible for the observed behavior, which led to an expanded water filled channel structure, where water can accumulate to facilitate proton diffusion as H3O+ through the channels. To confirm this assumption, the morphology of the recycled membranes will be investigated by in situ SAXS measurements at different temperatures and degrees of hydration.[1] I. Staffell, D. Scamman, A. Velazquez Abad, P. Balcombe, P. E. Dodds, P. Ekins, N. Shah, K. R. Ward, Energy Environ. Sci. 2019, 12, 463–491.[2] J. Fan, M. Chen, Z. Zhao, Z. Zhang, S. Ye, S. Xu, H. Wang, H. Li, Nat. Energy 2021, 6, 475–486.[3] D. Papageorgopoulos, Fuel Cell R&D Overview. 2019 Annual Merit Review and Peer Evaluation Meeting, 2019.[4] Q. Xu, X. Chen, S. Wang, C. Guo, Y. Niu, R. Zuo, Z. Yang, Y. Zhou, C. Xu, Energies 2022, 15, 8717.[5] H. F. Xu, X. Wang, Z. G. Shao, I. M. Hsing, J. Appl. Electrochem. 2002, 32, 1337–1340.

Crystallinity in polymer electrolyte membranes used in H2 generators: Degradation mechanism from the perspective of recycling

Methanol-based electrolysis can be a prospective alternative for the reduction of energy consumption. Developing highly durable methanol-based electrolysers with small CO2 release can help achieve cheaper hydrogen. Further, to arrive at a circular economy in H2, recycling the precious components would play a major role. Several studies on catalyst recycling have overshadowed the need for recycling the proton exchange membrane. Membrane, which forms 25% of the device cost, need to be studied for its degradation and optimizing the operating parameters of the device have a big role to play in establishing recycling. Our previous studies concluded that the change in crystallinity of membrane from fuel cell was closely related to membrane properties. Herein, for the first time, we have correlated the crystallinity of the membrane retrieved from an electrochemical methanol-reformer to its degradation mechanism. The average crystallinity on the anode and cathode sides was observed to be increased drastically compared to a fuel cell. As observed from Fourier Transform Infrared Spectroscopy (FTIR), the presence of sulfonic acid anhydrides was considered one of the reasons for this increase in crystallinity. X-ray photoelectron spectroscopy (XPS) showed that carbon peaks in the side chain was devoid of α-OCF2, –CF3, indicating severe degradation. The probability of finding a degraded area on the anode side of the scanned recycled membrane was 88% and 55% for the cathode side. The severe degradation of amorphous side chains and formation of short chains had considerably increased the crystallinity. The disparity in the intensity of degradation on the anode and cathode sides of the membrane was confirmed by the percentage of crystallinity and XPS studies. Further, the severity of degradation on either side of the membrane from methanol-based Proton Exchange Membrane electrolysers makes them difficult for further reuse in hydrogen-based energy systems.

Recycled membrane for drinking water treatment with high iron and manganese concentrations

Membrane recycling by oxidative treatment is one alternative to minimize the impacts of the disposal of end-of-life (EoL) reverse osmosis (RO) membranes. In parallel, iron (Fe) and manganese (Mn) contamination in surface and groundwater is increasing. This study aims to develop recycled membranes that retain dissolved Fe and Mn from water for supply purposes. EoL RO membranes were recycled with sodium hypochlorite (NaClO, 10–12%) solution at exposure dose between 4000−80,000 ppm∙h to produce a recycled membrane with high flowrate and high Fe and Mn rejection. EoL RO treated by 40,000 ppm·h showed water permeability of 54.30 L∙h−1∙m−2∙bar−1 and Fe and Mn rejection of 99% and 65%, respectively. Potability for Mn (> 98%) was enhanced by integrating pre-oxidation stage with NaClO (5 mg∙L−1 of Cl- and pH 8) to the recycled membrane process. Recycled module performance was evaluated for water treatment from Paraopeba River on pilot scale, in continuous operation (51 h) and pressure of 1 bar. At pilot scale, recycled membrane obtained a water permeability of 40.33 L∙h−1∙m−2∙bar−1, like a moderately open ultrafiltration membrane. Fe and Mn removals were > 99% and > 90%, respectively, with high color and turbidity removal efficiency. Membrane recycling cost was predicted to be US$ 4.08/m², and the capital (CapEX) and operating (OpEX) expenditures for the single-household system was US$ 671.18 and US$ 22.52 to m3·day−1 of treated water. Therefore, the recycled membrane was shown to be efficient in removing dissolved Fe and Mn, and it is promising for decentralized water treatment.

Methane Based Continuous Culture of Methylosinus trichosporium for Production of Poly-3-hydroxybutyrate Using Membrane Recycle System

Methane Based Continuous Culture of Methylosinus trichosporium for Production of Poly-3-hydroxybutyrate Using Membrane Recycle System

Low-cost recycled end-of-life reverse osmosis membranes for water treatment at the point-of-use

Decentralized systems applied at the point-of-use (POU) could be an alternative for a safe drinking water supply in isolated regions and developing countries. Based on that, it was investigated the recycling of end-of-life reverse osmosis (EoL-RO) household modules as an alternative for groundwater treatment at the POU. The membranes were recycled through chemical oxidation using NaOCl (440,000 ppm h) and were validated in a long-term operation. The systems operated in a dead-end configuration mode without external energy requirements for permeation, only the hydraulic force provided by the water grid. The increase in permeability from 4.5 to 50.4 L/m2h.bar and decrease in salinity rejection from 99.4 to 11.6% suggests that the EoL-RO was effectively converted to ultrafiltration (UF). The recycled membrane still presented a lower resistance to filtration due to its porous characteristics (average pore size 0.04 ± 0.01 μm). In the perspective of POU application, the lower energy requirement for the recycled membranes compared to EoL-RO would represent advantages if compared to reverse osmosis household modules, more energy-demanding filters. Effective water treatment and a low fouling propensity were observed for long-term operation at the POU. The monitoring data demonstrates a steady permeate flux (21.2 ± 0.46 L/m2h) and filtration resistance (6.37 ± 0.16 × 1014 1/m), producing a total permeate volume (3,000 L) comparable with commercial filtration systems and in compliance with the 109 potability standards analyzed. From a broader perspective, the advantages of using recycled membranes could be extended to environmental aspects, preventing the production of waste from spent membranes and focusing on cleaner production of technical processes.

Synthesis of hydroxyapatite whisker membranes for use as biocompatible and recyclable filters for bacterial removal

Polymer nanofibers have been applied extensively for developing biocompatible filters to remove bacteria from aqueous solutions. However, recycling and reusing these polymer nanofibers is very difficult. In this study, hydroxyapatite whisker membranes were employed as biocompatible and recyclable filters for bacterial removal. Scanning electron microscopy observations showed that the membranes comprised numerous whiskers with diameters of 286 ± 97 nm, and a fibrous and porous structure. Bacterial filtration experiments showed that the membranes completely removed Staphylococcus aureus (model bacterium) from a bacterial suspension with a filtration efficiency of 100%. After bacterial filtration, the membranes could be recycled by removing the bacteria using the conventional sterilization method. Furthermore, the recycled membranes could be reused as filters for bacterial removal with a filtration efficiency of 100%.

The mammalian endocytic cytoskeleton

Clathrin-mediated endocytosis (CME) is the major route through which cells internalise various substances and recycle membrane components. Via the coordinated action of many proteins, the membrane bends and invaginates to form a vesicle that buds off—along with its contents—into the cell. The contribution of the actin cytoskeleton to this highly dynamic process in mammalian cells is not well understood. Unlike in yeast, where there is a strict requirement for actin in CME, the significance of the actin cytoskeleton to mammalian CME is variable. However, a growing number of studies have established the actin cytoskeleton as a core component of mammalian CME, and our understanding of its contribution has been increasing at a rapid pace. In this review, we summarise the state-of-the-art regarding our understanding of the endocytic cytoskeleton, its physiological significance, and the questions that remain to be answered.

Screening of recycled membrane with crystallinity as a fundamental property

The maximum cost incurred in building a Polymer Electrolyte Membrane fuel cell (PEMFC) can be attributed to the proton exchange membrane and platinum on carbon (PtC) catalyst. Recycling of these precious components after their life, has been speculated to increase the commercial viability of PEMFC. In this work, we have demonstrated a method of recycling membranes from end of life fuel cells, with low input energy and bereft of any HF gas emission, and also amenable for up-scale activity. Further, to date most of the research work on recycling have focused mainly on the procedure to extract the membrane and no correlation on understanding the condition of the membrane for reusability or recyclability has been reported. In this work, we have developed a relationship between the structural properties of the recycled membrane to the overall electrochemical performance, helpful in predicting the end application.

Novel housing designs for nanofiltration and ultrafiltration gravity-driven recycled membrane-based systems

Ultra-low pressure gravity-driven membrane (GDM) systems have the potential to be significantly less costly and complex than conventional membranes for water treatment applications. To build upon this inherent advantage, this study assesses the reuse of recycled membranes in GDM systems for producing drinking water. Two reverse osmosis spiral-wound modules were recycled into nanofiltration (NF)-like and ultrafiltration (UF)-like membranes via controlled exposure to free chlorine. To operate the recycled membranes, two housing devices, based on a simple fitting and an advanced end-caps design, were developed. The recycled membrane systems were tested under a range of conditions (submerged vs. external system configuration and continuous vs. intermittent filtration mode). Synthetic river water feed solutions were used in the tests where performance, fouling, and clogging were measured. NF-like recycled membranes resulted in poor salt rejection and low permeability (~1.7 L m−2 h−1 bar−1), but also in high rejection (>81%) of dissolved organic carbon. UF-like recycled membranes maintained their capacity to reject biopolymers (BP) (>74%) and featured up to 18-fold higher permeate rate than NF-like recycled membranes. The optimized operating conditions were found when the recycled membranes were housed in the end-caps device and operated intermittently (relaxation time plus forward flushing). Flushing reduced the fouling accumulation inside the membrane (only 12% and 40% of BP accumulation was observed in the NF-like and UF-like, respectively). However, the end-caps-based device was estimated to be more expensive during the economic analysis. To address this techno-economic trade-off, a decision-making tree was developed to select the appropriate configuration based upon the implementation context. Overall, this study concludes that these designs can serve as robust, low-cost (water production cost <1 USD ct. yr. L−1), and light-weight GDM alternatives. This study is beneficial for developing compact GDM systems based on recycled spiral-wound membranes for both rural areas and emergency response.

Exploring microcystin-degrading bacteria thriving on recycled membranes during a cyanobacterial bloom

Microcystins (MC) are highly toxic secondary metabolites produced by cyanobacterial blooms in many freshwater ecosystems used for recreational and drinking water purposes. So far, biological processes remain to be optimized for an efficient cyanotoxin removal, and new approaches are necessary to compete with physical-chemical treatments. In previous studies we provided a new concept of membrane biofilm reactor made of recycled material, in which a single MC-degrading bacterial strain was inoculated. The present study evaluates the capacity of bacterial consortia associated with freshwater cyanobacterial blooms to form biofilms on recycled membranes and remove MC. Three different discarded reverse osmosis (RO) membranes, previously used in desalination plants after treating brackish water (BWd), seawater (SWd) and brackish water but transformed into nanofiltration (BWt-NF), were exposed to a cyanobacterial bloom in San Juan reservoir (central Spain). Results showed that the three recycled membranes developed a bacterial community with MC removal capacity. Little differences in bacterial coverage and MC removal efficiency between membranes were observed after their exposure in the reservoir. High-throughput sequencing of 16S rRNA gene analysis showed similar bacterial community composition at the phylum level but dissimilar at the order level between the three membranes. This suggests possible surface selectivity on the attached bacterial community. The mlr− candidates such as Burkholderiales and Methylophilales were highly abundant in BWt-NF and BWd, respectively, while mlr+ candidates (e.g. Sphingomonadales) were low abundant in all membranes. Analysis of mlrA and mlrB genes used as markers for MC degradation following mlr-pathway confirmed the presence of this pathway in all membranes. These results suggest the co-existence of both genotypes in membrane-attached native biofilms. Therefore, this study confirms that recycled membranes are suitable support for many MC-degrading bacteria, thus giving value to discarded membranes for eco-friendly and low-cost biological filters.

Recycling of end-of-life reverse osmosis membranes: Comparative LCA and cost-effectiveness analysis at pilot scale

Reverse Osmosis (RO) is the most extended desalination technology implemented worldwide. However, RO desalination has some environmental challenges that must be resolved in order to comply with the circular economy principles. RO membranes have a short service life of 5–10 years, generating 14,000 tonnes annually of membrane waste that is landfilled yearly. In this work two pilot designs for recycling end-of-life (EoL) RO membranes are evaluated with LCA and cost effectiveness analysis. The study includes different types of transformations depending on: i) EoL RO membrane type (brackish water (BW) or sea water (SW)) and ii) recycling product (nanofiltration (NF) or ultrafiltration (UF)). Substitutability formulas were adapted to membrane technology and service life data gap. Therefore, two new indicators (minimum service life and service life ratio) were developed and estimated from the ILCD-Midpoint impact results of the recycling process and the avoided products. Cluster analysis was applied in contribution profiles for category grouping. LCA results show that the recycling process using the passive system (PS) has lower environmental performance than the active system (AS) in all the categories. The most environmentally interesting transformations are the BWRO into NF and UF and from SWRO into NF. The transformation from SWRO to UF does not seem to be technically competitive due to the low recycled membrane permeability evidenced during the LIFE-TRANSFOMEM project. Cluster analysis shows that the most relevant flows were NaClO, bisulphite and electricity use. The cost of the recycling process with the PS is €25.9–41.5/module, whilst using the AS is €54.5–73.75/module.

Free chlorine exposure dose (ppm·h) and its impact on RO membranes ageing and recycling potential

Spiral wound thin film composite (TFC) polyamide (PA) membranes dominate the desalination market. Despite the proven performance of reverse osmosis (RO) membranes, they are periodically replaced and usually disposed of in landfills. The present study investigates the effect of using a diverse combination of free chlorine solutions (from 1 to 12,240 ppm) and exposure times (from 0.5 to 6500 h) with two purposes, namely: i) to simulate accelerated membrane ageing (low free chlorine concentration solutions) and ii) to optimize the existing recycling process of end-of-life RO membranes. Membrane coupons were taken from 8″ diameter modules (pristine and old). Membrane permeability and rejection coefficients were obtained by filtering synthetic brackish water (BW). Membrane surfaces were characterized by SEM and ATR-FTIR techniques. This work shows distinct PA vulnerability depending on membrane design (brackish water (BWRO) and seawater (SWRO) reverse osmosis membranes). Results reveal that the use of the exposure level parameter (ppm·h) as an independent basis for comparing free chlorine exposure must be carefully employed during ageing assessments and monitoring transition between nanofiltration (NF)-like performance to ultrafiltration (UF)-like performance. However, it can be used consistently to convert end-of-life RO membrane into NF-like recycled membranes using concentrations higher than 10 ppm.

Bench and pilot scale performance assessment of recycled membrane converted from old nanofiltration membranes

ABSTRACTRecycling of end-of-life polyamide-based thin film composite (TFC) membranes is gaining interest in academic and industrial contexts. The effects of chlorine exposure on the performance of polyamide membranes result in an increase in membrane permeability, whereas the solute rejection decreases. Therefore, the controlled chemical conversion of old reverse osmosis (RO) membranes has been reported by some previous papers. The objectives of this study were to assess recycling of old nanofiltration (NF) membrane, to assess the performance of the recycled membranes for a river water treatment application, and to conduct preliminary cost evaluations. Recycling technique consisted of exposing the membrane to a sodium hypochlorite solution in order to remove its polyamide layer and conversion to a low-pressure membrane. The work conducted bench scale and long-time pilot tests, and the recycled membranes showed a low fouling tendency. The difference between some results in bench- and pilot scale underscores the importance of evaluating design parameters using pilot scale units. Based on the cost analysis, the total cost of chemical recycling end-of-line NF membranes for a river water treatment is approximately 1.1% of the cost of using a new UF membrane. There is a great potential in using recycled membranes for rivers water treatments.

Experimental and Modeling Study of Galactosyl-Oligosaccharides Formation in Continuous Recycle Membrane Reactors (CRMR)

Experimental and Modeling Study of Galactosyl-Oligosaccharides Formation in Continuous Recycle Membrane Reactors (CRMR)

Biosynthesis of Oligodextrans Through Synergistic Catalysis of Dextransucrase and Dextranase in a Recycle Membrane Bioreactor

A continuous synthesis process for the production of oligodextrans from sucrose by using dextransucrase and dextranase in a recycle ultrafiltration membrane bioreactor was developed. During continuous oligodextrans synthesis, changes in weight-average molecular weight (Mw) and polydispersity index (D value) in the second feed tank (i) were monitored by high-performance gel permeation chromatography. Mw decreased with increasing reaction time, resulting in an increasingly homologous solution of low Mw oligodextrans (approximately 1 × 104 Da). The D value of the oligodextrans produced was nearly 1.0. In addition, the polymer degradation model well described the kinetics of Mw changes in oligodextrans. Results showed that recycle membrane bioreactor coupled with dextransucrase and dextranase is a simple and effective method that can be used to produce and improve the quality of oligodextrans.

CO2 capture from natural gas power plants using selective exhaust gas recycle membrane designs

This paper describes membrane processes to capture the CO2 produced by combustion gas turbines in natural gas combined cycle power plants. Because combustion turbines typically use a large excess of air, the resulting turbine exhaust gas is relatively dilute (only 3–4% CO2), making subsequent CO2 capture difficult and costly. Previously, we’ve shown that a membrane process can be used to selectively recycle CO2 to the combustion step, which significantly increases the CO2 content in the exhaust gas. In this way, selective exhaust gas recycle (S-EGR) makes CO2 capture energetically easier. Here, various membrane design concepts incorporating S-EGR are described and compared. A combination of S-EGR with non-selective exhaust gas recycle (EGR) is shown to offer advantages in reduced capital, while retaining most of the energy benefits of S-EGR alone. For all of the membrane designs analyzed, the energy and cost of capture vary with the capture rate. Generally, if flue gas compression is not used, the lowest capture cost ($/tonne CO2) for membranes occurs at partial capture rates of 60–70%. Of the process designs studied, the lowest cost of capture (∼$44/t) is achieved by an integrated turbine/membrane design that would require changes to existing turbines.

Optimization of vanadium (IV) extraction from stone coal leaching solution by emulsion liquid membrane using response surface methodology

In order to further improve the vanadium (IV) extraction from stone coal leaching solution in one step and reduce the reagent consumption by emulsion liquid membrane (ELM), the experiments using response surface methodology (RSM) was investigated. The liquid membrane was composed of paraffin as membrane stabilizer, D2EHPA as mobile carrier, span80 as surfactant and H2SO4 as stripping solution. Emulsification speed and emulsification time in emulsion formation was optimized to obtain a stable emulsion. An orthogonal 24 Box–Behnken design (BBD) having five replicates at the center point was used to estimate the coefficients of the response function. The linear effects, square effects and interactive effects of the parameters were analyzed by ANOVA. In addition, the signification of the parameters was also ranked. In the further study, the effect of electric demulsification and membrane recycle ability were studied under the optimized parameters. All of the results revealed that RSM was successfully used to optimize the extraction of V (IV) via ELM and indicated the potential industrially application for vanadium concentration and purification in one step from stone coal acid leaching solution.

CO2 capture from natural gas combined cycles by CO2 selective membranes

This paper performs a techno-economic analysis of natural gas-fired combined cycle (NGCC) power plants integrated with CO2 selective membranes for post-combustion CO2 capture. The configuration assessed is based on a two-membrane system: a CO2 capture membrane that separates the CO2 for final sequestration and a CO2 recycle membrane that selectively recycles CO2 to the gas turbine compressor inlet in order to increase the CO2 concentration in the gas turbine flue gas. Three different membrane technologies with different permeability and selectivity have been investigated. The mass and energy balances are calculated by integrating a power plant model, a membrane model and a CO2 purification unit model. An economic model is then used to estimate the cost of electricity and of CO2 avoided. A sensitivity analysis on the main process parameters and economic assumptions is also performed. It was found that a combination of a high permeability membrane with moderate selectivity as a recycle membrane and a very high selectivity membrane with high permeability used for the capture membrane resulted in the lowest CO2 avoided cost of 75US$/tCO2. This plant features a feed pressure of 1.5bar and a permeate pressure of 0.2bar for the capture membrane. This result suggests that membrane systems can be competitive for CO2 capture from NGCC power plants when compared with MEA absorption. However, to achieve significant advantages with respect to benchmark MEA capture, better membrane permeability and lower costs are needed with respect to the state of the art technology. In addition, due to the selective recycle, the gas turbine operates with a working fluid highly enriched with CO2. This requires redesigning gas turbine components, which may represent a major challenge for commercial deployment.

Attainability and minimum energy of multiple-stage cascade membrane systems

Process design and simulation of multi-stage membrane systems have been widely studied in many gas separation systems. However, general guidelines have not been developed yet for the attainability and the minimum energy consumption of a multi-stage membrane system. Such information is important for conceptual process design and thus it is the topic of this work. Using a well-mixed membrane model, it was determined that the attainability curve of multi-stage systems is defined by the pressure ratio and membrane selectivity. Using the constant recycle ratio scheme, the recycle ratio can shift the attainability behavior between single-stage and multi-stage membrane systems. When the recycle ratio is zero, all of the multi-stage membrane processes will decay to a single-stage membrane process. When the recycle ratio approaches infinity, the required selectivity and pressure ratio reach their absolute minimum values, which have a simple relationship with that of a single-stage membrane process, as follows: Sn=S1, γn=γ1, where n is the number of stages. The minimum energy consumption of a multi-stage membrane process is primarily determined by the membrane selectivity and recycle ratio. A low recycle ratio can significantly reduce the required membrane selectivity without substantial energy penalty. The energy envelope curve can provide a guideline from an energy perspective to determine the minimum required membrane selectivity in membrane process designs to compete with conventional separation processes, such as distillation.