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Black liquor is a highly alkaline liquid by-product of the kraft pulping process, rich in organic molecules (hemicelluloses, lignin, and organic acids) and inorganic pulping chemicals such as sodium salts and sulphur-containing compounds. The release of this wastewater without further treatment could have serious environmental and financial implications. Therefore, a costly treatment process is used nowadays. Nanofiltration has been studied in the last few years as a promising alternative to recycle the cooking chemicals required for the separation of lignin and cellulose, but the development of pH-stable membranes with the potential to operate at industrial scales is fundamental in order to make this possible. In this study, the filtration performance of two in-house made membranes is evaluated and compared with a commercial NF membrane to determine the viability of their use for the treatment of black liquor. For this purpose, filtration experiments with simulated black liquor were performed. We identified that Membrane A has the higher potential for this application due to its competitive permeate flux (ca. 24 L m−2 h−1 at a trans-membrane pressure of 21.5 bar), and high rejection of organic components and salts from the cooking liquor (on average, 92.50% for the TOC, 84.10% for the CO32−, 88.70% for the sulphates, 73.21% for the Na+, and 99.99% for the Mg2+).
Olenka Jibaja Valderrama; Karina Listiarini Zedda; Svetlozar Velizarov. Membrane Filtration Opportunities for the Treatment of Black Liquor in the Paper and Pulp Industry. Water 2021, 13, 2270 .
AMA StyleOlenka Jibaja Valderrama, Karina Listiarini Zedda, Svetlozar Velizarov. Membrane Filtration Opportunities for the Treatment of Black Liquor in the Paper and Pulp Industry. Water. 2021; 13 (16):2270.
Chicago/Turabian StyleOlenka Jibaja Valderrama; Karina Listiarini Zedda; Svetlozar Velizarov. 2021. "Membrane Filtration Opportunities for the Treatment of Black Liquor in the Paper and Pulp Industry." Water 13, no. 16: 2270.
Ion exchange membranes represent the main core of a number of separation processes such as electrodialysis, diffusion dialysis and Donnan dialysis, among others, at which the key role of these membranes is to control the transport of ionic species and their selective separation simultaneously. However, the ion exchange capacity, selective separation, stability and durability of ion exchange membranes in separation processes are especially limited under the use of natural feedwaters due to their heterogeneous and multivalent ionic composition, which leads to several fouling issues. This effect provokes a clear undesirable evolution with time in the initial membrane properties and characteristics, thus significantly decreasing the overall process performance in several applications. As a consequence, not only a further understanding of the fouling mechanisms and the interactions between foulant(s) and membrane(s) is crucial, but also development of adequate membrane cleaning protocols to alleviate the fouling impact after prolonged operations. Therefore, the aim of the present review is to define efficient membrane cleaning strategies to control and mitigate the impacts of fouling phenomena on ion exchange membranes in separation processes, paying special attention to the type of membrane, its characterization (before and after cleaning) and the target application. Herein, promising membrane cleaning approaches reported in the recent years are summarized and discussed. Alternative physical, chemical and mechanical cleanings (or their combination) can be considered, even though the control of the number of cleaning cycles, cleaning conditions and combination of cleaning approaches seem to be essential to achieve an optimum global cleaning efficiency. To sum up, although further research in understanding the role of fouling in material stability and degradation after cleaning is still needed, this review provides novel insights into the definition of the most appropriate membrane cleaning strategy in different ion exchange membrane separation processes.
Ivan Merino-Garcia; Svetlozar Velizarov. New insights into the definition of membrane cleaning strategies to diminish the fouling impact in ion exchange membrane separation processes. Separation and Purification Technology 2021, 277, 119445 .
AMA StyleIvan Merino-Garcia, Svetlozar Velizarov. New insights into the definition of membrane cleaning strategies to diminish the fouling impact in ion exchange membrane separation processes. Separation and Purification Technology. 2021; 277 ():119445.
Chicago/Turabian StyleIvan Merino-Garcia; Svetlozar Velizarov. 2021. "New insights into the definition of membrane cleaning strategies to diminish the fouling impact in ion exchange membrane separation processes." Separation and Purification Technology 277, no. : 119445.
Excessive ingestion of fluoride through the consumption of F−-rich drinking water could cause adverse effects to human health. For this reason, the WHO has fixed 1.5 mg/L as the maximum F- concentration for drinking water. In this work, a detailed geochemical characterization was performed to define the source of natural pollution of two groundwaters (samples Pc and Bg) coming from deep crystalline aquifers located in the Calabria region (southern Italy) and to define and optimize the most appropriate water treatment strategy. The samples were classified as a F− enriched NaHCO3 type of water. In particular, the F− concentrations observed were 30 mg/L and 8.9 mg/L for the Pc and Bg samples, respectively. Based on the acquired geochemical characterization knowledge, the groundwaters were treated by two thin-film composite NF membranes, namely SPR 10113 and SPR 10114 which have so far not been used for water defluoridation. It was found that the SPR 10114 membrane was able to guarantee water permeates with F− contents lower than the threshold value of 1.5 mg/L for both treated waters, whereas the fluoride content remained above the threshold value when the Pc sample was treated using the SPR 10113 membrane. The obtained permeates were characterized by a low ionic load and were not suitable for long-term consumption as drinking water. However, all of the produced waters did not need any further re-mineralizing processes for agricultural irrigation or other purposes.
Ilaria Fuoco; Carmine Apollaro; Alessandra Criscuoli; Rosanna De Rosa; Svetlozar Velizarov; Alberto Figoli. Fluoride Polluted Groundwaters in Calabria Region (Southern Italy): Natural Source and Remediation. Water 2021, 13, 1626 .
AMA StyleIlaria Fuoco, Carmine Apollaro, Alessandra Criscuoli, Rosanna De Rosa, Svetlozar Velizarov, Alberto Figoli. Fluoride Polluted Groundwaters in Calabria Region (Southern Italy): Natural Source and Remediation. Water. 2021; 13 (12):1626.
Chicago/Turabian StyleIlaria Fuoco; Carmine Apollaro; Alessandra Criscuoli; Rosanna De Rosa; Svetlozar Velizarov; Alberto Figoli. 2021. "Fluoride Polluted Groundwaters in Calabria Region (Southern Italy): Natural Source and Remediation." Water 13, no. 12: 1626.
Industrial adoption of nanofiltration (NF) for treatment of low-pH wastewater is hindered by the limited membrane lifetime at strongly acidic conditions. In this study, the electroplating wastewater (EPWW) filtration performance of a novel pH-stable NF membrane is compared against a commercial NF membrane and a reverse osmosis (RO) membrane. The presented membrane is relatively hydrophobic and has its isoelectric point (IEP) at pH 4.1, with a high and positive zeta potential of +10 mV at pH 3. A novel method was developed to determine the molecular weight cut-off (MWCO) at a pH of 2, with a finding that the membrane maintains the same MWCO (~500 Da) as under neutral pH operating conditions, whereas the commercial membrane significantly increases it. In crossflow filtration experiments with simulated EPWW, rejections above 75% are observed for all heavy metals (compared to only 30% of the commercial membrane), while keeping the same pH in the feed and permeate. Despite the relatively lower permeance of the prepared membrane (~1 L/(m2·h·bar) versus ~4 L/(m2·h·bar) of the commercial membrane), its high heavy metals rejection coupled with a very low acid rejection makes it suitable for acid recovery applications.
Ignacio Hegoburu; Karina Listiarini Zedda; Svetlozar Velizarov. Treatment of Electroplating Wastewater Using NF pH-Stable Membranes: Characterization and Application. Membranes 2020, 10, 399 .
AMA StyleIgnacio Hegoburu, Karina Listiarini Zedda, Svetlozar Velizarov. Treatment of Electroplating Wastewater Using NF pH-Stable Membranes: Characterization and Application. Membranes. 2020; 10 (12):399.
Chicago/Turabian StyleIgnacio Hegoburu; Karina Listiarini Zedda; Svetlozar Velizarov. 2020. "Treatment of Electroplating Wastewater Using NF pH-Stable Membranes: Characterization and Application." Membranes 10, no. 12: 399.
The objective of this work is to develop an appropriate technology for environmentally sound membrane-based purification of a tannery effluent assuring, simultaneously, the recovery of chromium, considered as the most hazardous inorganic water pollutant extensively used in leather tanning. A comparison between the permeate fluxes obtained during treatment of a synthetic tannery effluent through nanofiltration (NF270 and NF90 membranes) and reverse osmosis (BW30 and SW30) membranes was first performed. Then, a dedicated polymeric membrane was prepared by coating chitosan (cs) on a polyethersulfone (PES) microfiltration membrane (cs-PES MFO22) support. The resulting membrane was characterized by Fourier Transforms Infrared Spectroscopy Attenuated Total Reflectance (FTIR-ATR), Emission Scanning Electronic Microscopy (SEM) to confirm the process of surface modification and cross-linking of chitosan with glutaraldehyde. This membrane was found to be highly effective for chromium removal (>99%), which was more than eight times higher in reference to monovalent cations (e.g., Na+ and K+) and more than six times higher in reference to the divalent cations (Mg2+ and Ca2+) studied. The reverse osmosis permeate conforms to local Algerian regulations regarding being discharged directly into the natural environment (in this case, Reghaia Lake) or into urban sewers linked to wastewater biological treatment stations. While the SW30 membrane proved to be the most effective for purification of the tannery effluent, the chitosan modified membrane proved to be appropriate for recovery of chromium from the reverse osmosis concentrate.
Asmaa Zakmout; Fatma Sadi; Carla A. M. Portugal; João G. Crespo; Svetlozar Velizarov. Tannery Effluent Treatment by Nanofiltration, Reverse Osmosis and Chitosan Modified Membranes. Membranes 2020, 10, 378 .
AMA StyleAsmaa Zakmout, Fatma Sadi, Carla A. M. Portugal, João G. Crespo, Svetlozar Velizarov. Tannery Effluent Treatment by Nanofiltration, Reverse Osmosis and Chitosan Modified Membranes. Membranes. 2020; 10 (12):378.
Chicago/Turabian StyleAsmaa Zakmout; Fatma Sadi; Carla A. M. Portugal; João G. Crespo; Svetlozar Velizarov. 2020. "Tannery Effluent Treatment by Nanofiltration, Reverse Osmosis and Chitosan Modified Membranes." Membranes 10, no. 12: 378.
Rechargeable Zinc (Zn)-air batteries are considered to be very attractive candidates for large-scale electricity storage due to their high volumetric energy density, high safety, economic feasibility and environmental friendliness. In Zn-air batteries, the membrane allows the transport of OH− ions between the air electrode and the Zn electrode while providing a physical barrier between the two electrodes in order to prevent electrical short circuits. The performance of this battery is greatly affected by the physicochemical properties of the employed membrane. However, the development of appropriate membranes has received insufficient attention. In this paper, an overview of recent developments and a critical discussion of the state-of-the-art studies focusing on membranes for Zn-air batteries are provided. The membranes are classified in seven categories, which are discussed in light of their structure, properties and performances in Zn-air battery. Moreover, membrane synthesis and modification strategies to minimize the crossover of zincate ions and formation/growth of Zn-dendrites are presented. Finally, the remaining key challenges related to the membranes and the most promising future research directions are provided. The main objective of this work is to provide guidance for researchers and industries for the selection and development of appropriate membranes with the ultimate goal of commercializing rechargeable Zn-air batteries.
Misgina Tilahun Tsehaye; Fannie Alloin; Cristina Iojoiu; Ramato Ashu Tufa; David Aili; Peter Fischer; Svetlozar Velizarov. Membranes for zinc-air batteries: Recent progress, challenges and perspectives. Journal of Power Sources 2020, 475, 228689 .
AMA StyleMisgina Tilahun Tsehaye, Fannie Alloin, Cristina Iojoiu, Ramato Ashu Tufa, David Aili, Peter Fischer, Svetlozar Velizarov. Membranes for zinc-air batteries: Recent progress, challenges and perspectives. Journal of Power Sources. 2020; 475 ():228689.
Chicago/Turabian StyleMisgina Tilahun Tsehaye; Fannie Alloin; Cristina Iojoiu; Ramato Ashu Tufa; David Aili; Peter Fischer; Svetlozar Velizarov. 2020. "Membranes for zinc-air batteries: Recent progress, challenges and perspectives." Journal of Power Sources 475, no. : 228689.
Reverse electrodialysis (RED) technology represents a promising electro-membrane process for renewable energy harvesting from aqueous streams with different salinity. However, the performance of the key components of the system, that is, the ion exchange membranes, is limited by both the presence of multivalent ions and fouling phenomena, thus leading to a reduced generated net power density. In this context, the behavior of anion exchange membranes (AEMs) in RED systems is more severely affected, due to the undesirable interactions between their positively charged fixed groups and, mostly negatively charged, foulant materials present in natural streams. Therefore, controlling both the monovalent anion permselectivity and the membrane surface hydrophilicity is crucial. In this respect, different surface modification procedures were considered in the literature, to enhance the above-mentioned properties. This review reports and discusses the currently available approaches for surface modifications of AEMs, such as graft polymerization, dip coating, and layer-by-layer, among others, mainly focusing on preparing monovalent permselective AEMs with antifouling characteristics, but also considering hydrophilicity aspects and identifying the most promising modifying agents to be utilized. Thus, the present study aimed at providing new insights for the further design and development of selective, durable, and cost-effective modified AEMs for an enhanced RED process performance, which is indispensable for a practical implementation of this electro-membrane technology at an industrial scale.
Francis Kotoka; Ivan Merino-Garcia; Svetlozar Velizarov. Surface Modifications of Anion Exchange Membranes for an Improved Reverse Electrodialysis Process Performance: A Review. Membranes 2020, 10, 160 .
AMA StyleFrancis Kotoka, Ivan Merino-Garcia, Svetlozar Velizarov. Surface Modifications of Anion Exchange Membranes for an Improved Reverse Electrodialysis Process Performance: A Review. Membranes. 2020; 10 (8):160.
Chicago/Turabian StyleFrancis Kotoka; Ivan Merino-Garcia; Svetlozar Velizarov. 2020. "Surface Modifications of Anion Exchange Membranes for an Improved Reverse Electrodialysis Process Performance: A Review." Membranes 10, no. 8: 160.
The performance of anion-exchange membranes (AEMs) in Reverse Electrodialysis is hampered by both presence of multivalent ions and fouling phenomena, thus leading to reduced net power density. Therefore, we propose a monolayer surface modification procedure to functionalize Ralex-AEMs with poly(acrylic) acid (PAA) in order to (i) render a monovalent permselectivity, and (ii) minimize organic fouling. Membrane surface modification was carried out by putting heterogeneous AEMs in contact with a PAA-based aqueous solution for 24 h. The resulting modified membranes were firstly characterized by contact angle, water uptake, ion exchange capacity, fixed charge density, and swelling degree measurements, whereas their electrochemical responses were evaluated through cyclic voltammetry. Besides, their membrane electro-resistance was also studied via electrochemical impedance spectroscopy analyses. Finally, membrane permselectivity and fouling behavior in the presence of humic acid were evaluated through mass transport experiments using model NaCl containing solutions. The use of modified PAA-AEMs resulted in a significantly enhanced monovalent permselectivity (sulfate rejection improved by >35%) and membrane hydrophilicity (contact angle decreased by >15%) in comparison with the behavior of unmodified Ralex-AEMs, without compromising the membrane electro-resistance after modification, thus demonstrating the technical feasibility of the proposed membrane modification procedure. This study may therefore provide a feasible way for achieving an improved Reverse Electrodialysis process efficiency.
Ivan Merino-Garcia; Francis Kotoka; Carla A.M. Portugal; João G. Crespo; Svetlozar Velizarov. Characterization of Poly(Acrylic) Acid-Modified Heterogenous Anion Exchange Membranes with Improved Monovalent Permselectivity for RED. Membranes 2020, 10, 134 .
AMA StyleIvan Merino-Garcia, Francis Kotoka, Carla A.M. Portugal, João G. Crespo, Svetlozar Velizarov. Characterization of Poly(Acrylic) Acid-Modified Heterogenous Anion Exchange Membranes with Improved Monovalent Permselectivity for RED. Membranes. 2020; 10 (6):134.
Chicago/Turabian StyleIvan Merino-Garcia; Francis Kotoka; Carla A.M. Portugal; João G. Crespo; Svetlozar Velizarov. 2020. "Characterization of Poly(Acrylic) Acid-Modified Heterogenous Anion Exchange Membranes with Improved Monovalent Permselectivity for RED." Membranes 10, no. 6: 134.
The present work investigates the performance of an ion-exchange membrane process for arsenate removal, consisting in integrating Donnan dialytic transport of arsenic with its simultaneous precipitation in a separate receiver compartment. The process performance was improved by adding a bicarbonate-carbonate buffer in the receiver solution, where iron (III) chloride was used to precipitate the arsenic. This system allowed to maintain the treated water pH within the acceptable drinking water range of 6–9, without further control. A Response Surface Methodology (RSM) was used to infer about the effect of the supply water characteristics (initial arsenic concentration and pH) and operating conditions (mass ratio of iron to arsenic) on the degree of arsenic removal. It was found that the initial pH of the receiver solution was also a required input to predict accurately the arsenic concentration in the treated water (for a predefined treatment time). The model developed has a fitting R2 value of 0.99 and a prediction error of 6.6 µg/L of As. The methodology presented permits to develop a simple decision tool (either through the use of equations or visual plots) to determine the effective amount of iron to be used in the treatment of As contaminated water.
Mafalda Pessoa Lopes; Claudia F. Galinha; João G. Crespo; Svetlozar Velizarov. Optimisation of arsenate removal from water by an integrated ion-exchange membrane process coupled with Fe co-precipitation. Separation and Purification Technology 2020, 246, 116894 .
AMA StyleMafalda Pessoa Lopes, Claudia F. Galinha, João G. Crespo, Svetlozar Velizarov. Optimisation of arsenate removal from water by an integrated ion-exchange membrane process coupled with Fe co-precipitation. Separation and Purification Technology. 2020; 246 ():116894.
Chicago/Turabian StyleMafalda Pessoa Lopes; Claudia F. Galinha; João G. Crespo; Svetlozar Velizarov. 2020. "Optimisation of arsenate removal from water by an integrated ion-exchange membrane process coupled with Fe co-precipitation." Separation and Purification Technology 246, no. : 116894.
Membrane processes are of crucial importance for downstream processing in biotechnology. This is due to their selectivity and the mild operating conditions, enabling to extract target products without damages caused by overheating and chemical agents. Besides the most spread membrane processes like ultrafiltration and reverse osmosis, electrodialysis is very important for removal and extraction of electrically charged products, i. e. anions of organic acids, some antibiotics, etc. The electrodialysis process can be organized in batch or continuous mode. On the other hand, in the electro-crossflow filtration, the transport of target solutes across the membrane is guided by two main driving forces, the transmembrane pressure and the electric potential. This combination enables various possibilities for more selective and efficient downstream processing in biotechnology. This chapter provides a brief overview of recent achievements of electrodialysis in selected bioproducts separations and recovery. A special focus, including original experimental data, is then given to electro-filtration, which is a powerful tool creating new opportunities for performing separations on the basis of both electric charge and particle size differences.
Zdravka Lazarova; Venko Beschkov; Svetlozar Velizarov. Electro-membrane separations in biotechnology. Physical Sciences Reviews 2020, 5, 1 .
AMA StyleZdravka Lazarova, Venko Beschkov, Svetlozar Velizarov. Electro-membrane separations in biotechnology. Physical Sciences Reviews. 2020; 5 (8):1.
Chicago/Turabian StyleZdravka Lazarova; Venko Beschkov; Svetlozar Velizarov. 2020. "Electro-membrane separations in biotechnology." Physical Sciences Reviews 5, no. 8: 1.
A novel cellulose-based cross-linked polymer, dicarboxymethyl cellulose (DCMC), has been synthesized and used for methylene blue (MB) removal. Inductively coupled plasma atomic emission spectrometry (ICP-AES), Fourier-transform infrared spectroscopy (FTIR), nitrogen porosimetry, and optical microscopy were employed to characterize the structure of the cellulose-based adsorbent. The number of carboxylate groups per gram of polymer (CG) was calculated with sodium content determined by ICP-AES. Systematic equilibrium and kinetic adsorption studies were performed to assess the polymer suitability for dye removal. The effect of pH on its adsorption capacity was also studied and the equilibrium adsorption data was analyzed using Langmuir, Freundlich, and Sips isotherms. At pH = 3, the adsorption isotherms followed the Langmuir model with a maximum adsorption capacity of 887.6 mg/g. At pH = 6.4, the adsorption isotherms produced S-shape curves and were best fitted with the Sips model. The maximum MB uptake increased to 1354.6 mg/g. Pseudo first-order and second-order models were used to fit the kinetic data. A pseudo second-order kinetic model provided the best correlation for the adsorption of MB onto DCMC. Adsorption coupled with membrane filtration achieved 95% methylene blue removal and DCMC can be successfully regenerated and reused in consecutive experiments.
Diana Gago; Ricardo Chagas; Luísa M. Ferreira; Svetlozar Velizarov; Isabel Coelhoso. A Novel Cellulose-Based Polymer for Efficient Removal of Methylene Blue. Membranes 2020, 10, 13 .
AMA StyleDiana Gago, Ricardo Chagas, Luísa M. Ferreira, Svetlozar Velizarov, Isabel Coelhoso. A Novel Cellulose-Based Polymer for Efficient Removal of Methylene Blue. Membranes. 2020; 10 (1):13.
Chicago/Turabian StyleDiana Gago; Ricardo Chagas; Luísa M. Ferreira; Svetlozar Velizarov; Isabel Coelhoso. 2020. "A Novel Cellulose-Based Polymer for Efficient Removal of Methylene Blue." Membranes 10, no. 1: 13.
Acid mine drainage (AMD) is a severe form of environmental pollution that has the potential to contaminate surface and ground waters by introducing heavy metals and lowering the pH. The feasibility of using nanofiltration (NF) as a potentially attractive and cost-effective remediation method to treat acid mine drainage was investigated in this study. The performance of an acid-stable NF membrane focusing on the effects of the water pH and membrane charge on ion rejection was systematically studied. A single salt solution experiment showed that Mg, Cu, and Mn containing species were highly rejected at above 97%. Below the membrane iso-electric point (IEP), Mn showed an increased rejection of 99%, while Mg and Mn rejections were relatively constant within the investigated pH range of pH 2 to 7. Rejection of monovalent Cl− decreased with increasing concentration of an accompanying divalent SO42−, showing that Donnan related effects are more prominent at higher ionic concentrations. The sulfate rejection decreased drastically below pH 3 due to the formation of HSO4−, which permeated through the membrane, which can be utilized as a way of separation of the metals from the accompanying sulfur-containing compounds. For mixed salt solutions, rejection of silicate dropped from 52% to 38% when magnesium sulfate was added, owing to shielding of the membrane surface charge by Mg2+ ions. The NF process performance with a simulated AMD solution was found to be similar to that with model salt solution experiments, both in terms of ion rejection values and general pH-dependent rejection trends. The results obtained can be used as a fast preliminary tool for evaluating the feasibility of using NF for treating AMD with a given ionic composition and pH.
Ye Wee Siew; Karina Listiarini Zedda; Svetlozar Velizarov. Nanofiltration of Simulated Acid Mine Drainage: Effect of pH and Membrane Charge. Applied Sciences 2020, 10, 400 .
AMA StyleYe Wee Siew, Karina Listiarini Zedda, Svetlozar Velizarov. Nanofiltration of Simulated Acid Mine Drainage: Effect of pH and Membrane Charge. Applied Sciences. 2020; 10 (1):400.
Chicago/Turabian StyleYe Wee Siew; Karina Listiarini Zedda; Svetlozar Velizarov. 2020. "Nanofiltration of Simulated Acid Mine Drainage: Effect of pH and Membrane Charge." Applied Sciences 10, no. 1: 400.
Environment-friendly production of power and clean water is one of the major goals of 2030 Agenda for Sustainable Development, and can be achieved by emerging electromembrane processes, such as reverse electrodialysis (RED) and membrane capacitive deionisation (MCDI). RED generates electricity from salinity gradient energy sources, while MCDI desalinates (mainly) brackish water. However, fouling, scaling, stack channels clogging and undesired uphill ionic transport can reduce the power output and salt removal efficiency in RED and MCDI, respectively. A practical overview of current problems and challenges of operating and monitoring these processes under real conditions is provided. Appropriate mitigation approaches, which might include feed water pre-treatment, in-situ cleaning strategies and/or development of new antifouling ion-exchange membranes (IEMs) are disclosed. First, a description, analysis and (when possible) normalised comparison of the performance of available RED and MCDI stacks, employing natural saline streams, is presented. Afterwards, it is discussed how fouling formation can be detected, monitored and characterised, which is essential to implement effective pre-treatment and cleaning strategies. Finally, sustainable ways for preparation of appropriate IEMs are selected and presented.
Sylwin Pawlowski; Rosa M. Huertas; Cláudia F. Galinha; João G. Crespo; Svetlozar Velizarov. On operation of reverse electrodialysis (RED) and membrane capacitive deionisation (MCDI) with natural saline streams: A critical review. Desalination 2019, 476, 114183 .
AMA StyleSylwin Pawlowski, Rosa M. Huertas, Cláudia F. Galinha, João G. Crespo, Svetlozar Velizarov. On operation of reverse electrodialysis (RED) and membrane capacitive deionisation (MCDI) with natural saline streams: A critical review. Desalination. 2019; 476 ():114183.
Chicago/Turabian StyleSylwin Pawlowski; Rosa M. Huertas; Cláudia F. Galinha; João G. Crespo; Svetlozar Velizarov. 2019. "On operation of reverse electrodialysis (RED) and membrane capacitive deionisation (MCDI) with natural saline streams: A critical review." Desalination 476, no. : 114183.
The hydrodynamics of electrodialysis and reverse electrodialysis is commonly studied by neglecting membrane deformation caused by transmembrane pressure (TMP). However, large frictional pressure drops and differences in fluid velocity or physical properties in adjacent channels may lead to significant TMP values. In previous works, we conducted one-way coupled structural-CFD simulations at the scale of one periodic unit of a profiled membrane/channel assembly and computed its deformation and frictional characteristics as functions of TMP. In this work, a novel fluid–structure interaction model is presented, which predicts, at the channel pair scale, the changes in flow distribution associated with membrane deformations. The continuity and Darcy equations are solved in two adjacent channels by treating them as porous media and using the previous CFD results to express their hydraulic permeability as a function of the local TMP. Results are presented for square stacks of 0.6-m sides in cross and counter flow at superficial velocities of 1 to 10 cm/s. At low velocities, the corresponding low TMP does not significantly affect the flow distribution. As the velocity increases, the larger membrane deformation causes significant fluid redistribution. In the cross flow, the departure of the local superficial velocity from a mean value of 10 cm/s ranges between −27% and +39%.
Giuseppe Battaglia; Luigi Gurreri; Andrea Cipollina; Antonina Pirrotta; Svetlozar Velizarov; Michele Ciofalo; Giorgio Micale. Fluid–Structure Interaction and Flow Redistribution in Membrane-Bounded Channels. Energies 2019, 12, 4259 .
AMA StyleGiuseppe Battaglia, Luigi Gurreri, Andrea Cipollina, Antonina Pirrotta, Svetlozar Velizarov, Michele Ciofalo, Giorgio Micale. Fluid–Structure Interaction and Flow Redistribution in Membrane-Bounded Channels. Energies. 2019; 12 (22):4259.
Chicago/Turabian StyleGiuseppe Battaglia; Luigi Gurreri; Andrea Cipollina; Antonina Pirrotta; Svetlozar Velizarov; Michele Ciofalo; Giorgio Micale. 2019. "Fluid–Structure Interaction and Flow Redistribution in Membrane-Bounded Channels." Energies 12, no. 22: 4259.
The feasibility of recovering phosphate from Algerian industrial wastewater was evaluated by a combination of membrane processes: nanofiltration, diananofiltration and Donnan dialysis. First, the separation of phosphate from a synthetic target effluent with an ionic composition resembling that of the industrial one was tested by nanofiltration using three commercial flat sheet membranes NF270, NF90 (Dow Filmtec) and Desal 5-DK (GE Osmonics) investigating the effect of the effluent pH. The results obtained show that the NF270 membrane assures the highest transport and recovery of phosphate. Afterwards, a diananofiltration process was developed with the optimal process parameters identified. A complete recovery of phosphate was achieved with one additional step of diananofiltration. Finally, Donnan dialysis was also investigated for further purification and preconcentration of phosphate from the permeates previously obtained. The performance of four anion exchange membranes with distinct properties: Neosepta AXE01, Neosepta ACS, Ralex AMH-PES and PC200D was investigated and compared, using chloride as a “driving” counterion in a KCl containing receiver solution. It was found that the AXE01 membrane gives the highest transport and phosphate recovery, achieving a 6-fold increase of the phosphate concentration in the receiver solution, in just one Donnan dialysis step.
A. Noubli; D.E. Akretche; João Crespo; S. Velizarov. Complementary membrane-based processes for recovery and preconcentration of phosphate from industrial wastewater. Separation and Purification Technology 2019, 234, 116123 .
AMA StyleA. Noubli, D.E. Akretche, João Crespo, S. Velizarov. Complementary membrane-based processes for recovery and preconcentration of phosphate from industrial wastewater. Separation and Purification Technology. 2019; 234 ():116123.
Chicago/Turabian StyleA. Noubli; D.E. Akretche; João Crespo; S. Velizarov. 2019. "Complementary membrane-based processes for recovery and preconcentration of phosphate from industrial wastewater." Separation and Purification Technology 234, no. : 116123.
The history of the potential and electrical current evolution of an industrial chlor-alkali membrane electrolyser is a powerful tool to track its operational efficiency progress over time and for deciding the required maintenance instants. For this reason, the performance of a dedicated industrial NaCl electrolyser was systematically analysed as a function of its service time for about 8 years, recording the cell potential versus current density. The documented potential values were normalized taking into account the initial current density, which allowed to reduce data scattering due to small fluctuations of the current density values. The ohmic overpotential contribution, associated to the ion-exchange membranes, showed an average relative error smaller than 3% and the activation overpotential, related to the electrodes’ performance, displayed an average relative error of 6%. Thus, the proposed approach enables rigorous assessing of the performance of industrial chlor-alkali membrane electrolysers for adequate scheduling of their maintenance, which leads to significant operational and economic improvements of the chlor-alkali process.
Filipa Franco; Jorge Prior; Svetlozar Velizarov; Adélio Mendes. A Systematic Performance History Analysis of a Chlor-Alkali Membrane Electrolyser under Industrial Operating Conditions. Applied Sciences 2019, 9, 284 .
AMA StyleFilipa Franco, Jorge Prior, Svetlozar Velizarov, Adélio Mendes. A Systematic Performance History Analysis of a Chlor-Alkali Membrane Electrolyser under Industrial Operating Conditions. Applied Sciences. 2019; 9 (2):284.
Chicago/Turabian StyleFilipa Franco; Jorge Prior; Svetlozar Velizarov; Adélio Mendes. 2019. "A Systematic Performance History Analysis of a Chlor-Alkali Membrane Electrolyser under Industrial Operating Conditions." Applied Sciences 9, no. 2: 284.
Profiled membranes (also known as corrugated membranes, micro-structured membranes, patterned membranes, membranes with designed topography or notched membranes) are gaining increasing academic and industrial attention and recognition as a viable alternative to flat membranes. So far, profiled ion exchange membranes have shown to significantly improve the performance of reverse electrodialysis (RED), and particularly, electrodialysis (ED) by eliminating the spacer shadow effect and by inducing hydrodynamic changes, leading to ion transport rate enhancement. The beneficial effects of profiled ion exchange membranes are strongly dependent on the shape of their profiles (corrugations/patterns) as well as on the flow rate and salts’ concentration in the feed streams. The enormous degree of freedom to create new profile geometries offers an exciting opportunity to improve even more their performance. Additionally, the advent of new manufacturing methods in the membrane field, such as 3D printing, is anticipated to allow a faster and an easier way to create profiled membranes with different and complex geometries.
Sylwin Pawlowski; João G. Crespo; Svetlozar Velizarov. Profiled Ion Exchange Membranes: A Comprehensible Review. International Journal of Molecular Sciences 2019, 20, 165 .
AMA StyleSylwin Pawlowski, João G. Crespo, Svetlozar Velizarov. Profiled Ion Exchange Membranes: A Comprehensible Review. International Journal of Molecular Sciences. 2019; 20 (1):165.
Chicago/Turabian StyleSylwin Pawlowski; João G. Crespo; Svetlozar Velizarov. 2019. "Profiled Ion Exchange Membranes: A Comprehensible Review." International Journal of Molecular Sciences 20, no. 1: 165.
Olive pomace is a semi-solid paste resulting from the two-phase olive oil production, being the most significant waste generated by this agro-industry. Olive pomace is reported as an environmental hazard due to its high content in phenolic compounds (phytotoxic). Nevertheless, these compounds, when recovered, can have impactful actions in different human physiological conditions, namely, skin protection, dysfunction treatment or diseases prevention. Therefore, their recovery from olive pomace is crucial for environmental and economical sustainability, without forgetting the functional challenge. In a previous work, lipid and aqueous fractions of olive pomace were studied regarding its major bioactive compounds. The present research aims to describe an environmentally friendly integrated approach to extract and concentrate (by a pressure-driven membrane processing) the phytotoxic compounds of olive pomace. Three types of polymeric composite membranes (NF90, NF270 and BW30) were tested. The composition of the resulting streams (permeates and concentrates) were compared and the process efficiency assessed based on: (1) antioxidant activity and total phenolic and flavonoid contents; (2) inorganic elemental composition (by Inductively Coupled Plasma Atomic Emission Spectroscopy); (3) pH, conductivity and total organic carbon; and (4) permeate flux, membranes' apparent target solutes rejection and fouling index. The BW30 membrane presented the lowest fouling index and was the most effective for extracts concentration, with no phenolic compounds in the permeates, preventing completely the loss of such compounds. Moreover, the permeate obtained with the BW30 membrane satisfied the physicochemical features for crops irrigation.
Maria Antónia Nunes; Sylwin Pawlowski; Anabela Guedes da Costa; Rita C. Alves; M. Beatriz P.P. Oliveira; Svetlozar Velizarov. Valorization of olive pomace by a green integrated approach applying sustainable extraction and membrane-assisted concentration. Science of The Total Environment 2018, 652, 40 -47.
AMA StyleMaria Antónia Nunes, Sylwin Pawlowski, Anabela Guedes da Costa, Rita C. Alves, M. Beatriz P.P. Oliveira, Svetlozar Velizarov. Valorization of olive pomace by a green integrated approach applying sustainable extraction and membrane-assisted concentration. Science of The Total Environment. 2018; 652 ():40-47.
Chicago/Turabian StyleMaria Antónia Nunes; Sylwin Pawlowski; Anabela Guedes da Costa; Rita C. Alves; M. Beatriz P.P. Oliveira; Svetlozar Velizarov. 2018. "Valorization of olive pomace by a green integrated approach applying sustainable extraction and membrane-assisted concentration." Science of The Total Environment 652, no. : 40-47.
Highly porous monolithic alumina columns find a wide variety of applications, including in chromatography, due to increased surface area and good accessibility to the ligands and reduced diffusional hindrances. Several modelling approaches have been applied to describe experimentally observed flow behaviour in such materials, which morphology plays a key role in determining their hydrodynamic and mass transfer properties. In this work, a direct computational fluid dynamics (CFD) modelling approach is proposed to simulate flow behaviour in monolithic porous columns. The morphological structure of a fabricated alumina monolith was first reconstructed using 3D X-ray tomography data and, subsequently, OpenFOAM, an open-source CFD tool, was used to simulate the essential parameters for monoliths’ performance characterisation and optimisation, i.e. velocity and pressure fields, fluid streamlines, shear stress and residence time distribution (RTD). Moreover, the tortuosity of the monolith was estimated by a novel method, using the computed streamlines, and its value (∼1.1) was found to be in the same range of the results obtained by known experimental, analytical and numerical equations. Besides, it was observed (for the case of the monolith studied) that fluid transport was dominated by flow heterogeneities and advection, while the shear stress at pore mouths was significantly higher than in other regions. The proposed modelling approach, with expected high potential for designing target materials, was successfully validated by an experimentally obtained residence time distribution (RTD).
S. Pawlowski; N. Nayak; Martine Meireles; Carla Portugal; Svetlozar Velizarov; João Crespo. CFD modelling of flow patterns, tortuosity and residence time distribution in monolithic porous columns reconstructed from X-ray tomography data. Chemical Engineering Journal 2018, 350, 757 -766.
AMA StyleS. Pawlowski, N. Nayak, Martine Meireles, Carla Portugal, Svetlozar Velizarov, João Crespo. CFD modelling of flow patterns, tortuosity and residence time distribution in monolithic porous columns reconstructed from X-ray tomography data. Chemical Engineering Journal. 2018; 350 ():757-766.
Chicago/Turabian StyleS. Pawlowski; N. Nayak; Martine Meireles; Carla Portugal; Svetlozar Velizarov; João Crespo. 2018. "CFD modelling of flow patterns, tortuosity and residence time distribution in monolithic porous columns reconstructed from X-ray tomography data." Chemical Engineering Journal 350, no. : 757-766.
Polyethersulfone (PES) is one of the most commonly used polymers for preparation of ultrafiltration and nanofiltration membranes. However, oxidative degradation of PES-based membranes, which results from exposing the membranes to oxidative agents, is limiting their operational lifespan and possible areas of application. Despite the high need for a fundamental understanding of the detailed oxidative degradation mechanism(s) of PES membranes in order to improve the effectiveness of cleaning/disinfecting agents and/or develop PES membranes with a higher tolerance to oxidative agents, it still remains an insufficiently understood topic. Therefore, this review aims at analyzing and critically discussing the recent state-of-the-art on the degradation mechanisms of PES membranes, focusing on the effects of chlorine-based oxidants (mainly NaOCl) and H2O2. Strategies that can be useful for minimizing/preventing oxidative PES membranes attack are presented. Finally, further prospective study possibilities to fill in the existing research gaps in this area are highlighted.
Misgina Tilahun Tsehaye; Svetlozar Velizarov; Bart Van der Bruggen. Stability of polyethersulfone membranes to oxidative agents: A review. Polymer Degradation and Stability 2018, 157, 15 -33.
AMA StyleMisgina Tilahun Tsehaye, Svetlozar Velizarov, Bart Van der Bruggen. Stability of polyethersulfone membranes to oxidative agents: A review. Polymer Degradation and Stability. 2018; 157 ():15-33.
Chicago/Turabian StyleMisgina Tilahun Tsehaye; Svetlozar Velizarov; Bart Van der Bruggen. 2018. "Stability of polyethersulfone membranes to oxidative agents: A review." Polymer Degradation and Stability 157, no. : 15-33.