Characterization of anion exchange membranes with natural organic matter (NOM) during electrodialysis (original) (raw)
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Characterization of anion exchange membranes fouled with humate during electrodialysis
Journal of Membrane Science, 2002
Natural organic matter (NOM) is thought to be a major source of fouling during membrane filtration of natural waters. The organic matter present in surface waters was characterized in terms of its molecular weight distribution, acidity and electrokinetic properties. The fouling potentials of anion exchange membranes were predicted by the characterization. Changes in the physicochemical properties of anion exchange membranes were also examined during electrodialysis (ED) process of solutions containing NOM. The ED performances were evaluated for the three anion exchange membranes (AMX, AM-1 and ACM) in the presence of NOM. Fouling phenomena in terms of current efficiency and NaC1 flux were in good agreement with the fouling potentials predicted by the characterization results. Observations of the molecular weight distribution and the constituents of NOM revealed that the hydrophobic NOM fraction with high molecular weights deposited mainly on the membrane surface, providing fouling effects on the anion exchange membrane.
Desalination, 2009
Interest in desalination using membrane processes has increased with the growth of membrane science and technology. Fouling of ion exchange membranes is one of the most significant considerations in the operation of the electrodialysis desalination process. The influence of the adsorption capacity of foulants on the fouling potential was investigated in an electrodialysis desalination process in the presence of negatively charged organic foulants, humate, bovine serum albumin and sodium dodecylbenzenesulfonate (SDBS). The SDBS showed higher adsorption capacity on the anion exchange membrane surface than the other two foulants in the adsorption equilibrium experiments. Of three different organic foulants, the SDBS had a more severe fouling effect on the process performance in the electrodialysis desalination of synthetic brackish water, with irreversible fouling due to the high adsorption capacity. The study clearly showed that the adsorption capacity affects the fouling potential of the electrodialysis desalination process.
A Study on Biofouling and Cleaning of Anion Exchange Membranes for Reverse Electrodialysis
Membranes
This study covers the modification, (bio)fouling characterization, use, and cleaning of commercial heterogeneous anion exchange membranes (AEMs) to evaluate their feasibility for reverse electrodialysis (RED) applications. A surface modification with poly (acrylic) acid resulted in an improved monovalent perm-selectivity (decreased sulfate membrane transport rate). Moreover, we evaluated the (bio)fouling potential of the membrane using sodium dodecyl sulfate (SDS), sodium dodecyl benzenesulfonate (SDBS), and Aeromonas hydrophila as model organic foulants and a biofoulant, respectively. A detailed characterization of the AEMs (water contact angle, ion exchange capacity (IEC), scanning electron microscopy (SEM), cyclic voltammetry (CV), and Fourier Transform Infrared (FTIR) spectra) was carried out, verifying that the presence of such foulants reduces IEC and the maximum current obtained by CV. However, only SDS and SDBS affected the contact angle values. Cleaning of the biofouled mem...
Role of anion exchange membrane fouling in reverse electrodialysis using natural feed waters
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2019
Reverse electrodialysis (RED) is a process to harvest renewable energy from salinity gradients. Under lab conditions with artificial salt solutions, promising results have been achieved in recent years. However, in large scale industrial applications, natural waters are used and that poses challenges such as fouling. Fouling of anion exchange membranes (AEMs) by organic matter (e.g. humic acids) has been identified as a possible cause that lowers RED performance with natural waters. In this work, natural river and seawater at the Afsluitdijk (The Netherlands) are used to study the RED performance of six different AEMs. These AEMs are characterized before and after RED experiments with natural waters. The effect of natural fouling is found to be specific for each AEM and highly dependent on their respective chemistries and associated membrane properties. Firstly, aromatic AEMs with a low swelling degree showed a permselectivity decrease as well as membrane resistance increase. Secondly, aliphatic AEMs with a medium swelling degree experienced only a membrane resistance increase. Finally, only a decrease in permselectivity was observed for aliphatic AEMs with large swelling degrees. Subsequently, the effect of AEM fouling is compared to the observed decrease in RED performance and this shows that AEM fouling can only explain a minor part of the losses in open circuit voltage (OCV). The RED power densities dropped by 15-20% over 12 days, independent of the AEMs selected, while the reduced AEM performance could only explain 2-4% of this reduction in power density. This demonstrates that next to AEM fouling, also other factors, such as spacer fouling, are expected to be the dominant fouling mechanism, reducing the performance to a much larger extent.
Membranes, 2021
Electrodialysis (ED) was first established for water desalination and is still highly recommended in this field for its high water recovery, long lifetime and acceptable electricity consumption. Today, thanks to technological progress in ED processes and the emergence of new ion-exchange membranes (IEMs), ED has been extended to many other applications in the food industry. This expansion of uses has also generated several problems such as IEMs’ lifetime limitation due to different ageing phenomena (because of organic and/or mineral compounds). The current commercial IEMs show excellent performance in ED processes; however, organic foulants such as proteins, surfactants, polyphenols or other natural organic matters can adhere on their surface (especially when using anion-exchange membranes: AEMs) forming a colloid layer or can infiltrate the membrane matrix, which leads to the increase in electrical resistance, resulting in higher energy consumption, lower water recovery, loss of me...
Journal of Membrane Science, 2016
In this paper, the consequences of traditional chemical cleaning on anion-exchange membrane structure and properties are thoroughly assessed. A homogeneous anion-exchange membrane (AEM1) and a heterogeneous one (AEM2) were subjected to ageing protocols in 2 M NaOH and 2 M HCl up to 700 h at room temperature. Moreover, both membranes were exposed to cleaning cycles in which they were soaked alternatively in 0.1 M HCl and 0.1 M NaOH (30 min each) from 100 to 400 h to simulate the cleaning-in-place (CIP) procedure commonly used in industrial electrodialysis stacks. Exposure to strong acidic conditions did not result in severe changes of the physicochemical properties of AEM1. In contrast, strong alkaline conditions resulted in the transformation of poly(vinyl chloride) (PVC), i.e. the polymeric binder of AEM1, into a polyene structure as a consequence of dehydrochlorination enhanced by the presence of quaternary ammonium groups. Additionally, a small part of the functional sites were degraded by E1 or E2 elimination reactions. On the other hand, the cleaning cycles caused entanglement modifications in the semi-interpenetrating polymer network structure of AEM1. This was a consequence of the constant changing of the equilibrating solutions nature, which led to membrane inflate-deflate sequences. Therefore, membrane toughness was deteriorated, thus leading to the formation of cracks and fractures, as observed before on the same type of membrane after industrial electrodialysis in which traditional CIP is performed through acid-base sequences. In contrast, the heterogeneous AEM2 suffered degradation in strong acid conditions, whereas it seemed to be more resistant than AEM1 in strong alkaline conditions. Regarding the HCl-NaOH cycles, modifications were more significant for AEM2. This investigation permitted to correlate membrane ageing resulting from such ex-situ acid-base cleaning cycles and that suffered after conventional electrodialysis during traditional CIP.
Membranes, 2021
Ion-exchange membranes (IEMs) are increasingly used in dialysis and electrodialysis processes for the extraction, fractionation and concentration of valuable components, as well as reagent-free control of liquid media pH in the food industry. Fouling of IEMs is specific compared to that observed in the case of reverse or direct osmosis, ultrafiltration, microfiltration, and other membrane processes. This specificity is determined by the high concentration of fixed groups in IEMs, as well as by the phenomena inherent only in electromembrane processes, i.e., induced by an electric field. This review analyzes modern scientific publications on the effect of foulants (mainly typical for the dairy, wine and fruit juice industries) on the structural, transport, mass transfer, and electrochemical characteristics of cation-exchange and anion-exchange membranes. The relationship between the nature of the foulant and the structure, physicochemical, transport properties and behavior of ion-exch...
Journal of Membrane Science, 2019
Anion exchange membrane (AEMs) fouling is a serious problem influencing membrane performance during electrodialysis process(ED), which would increase power consumption and reduce water recovery. In this paper, an aliphatic anion-exchange membrane was prepared from quaternized polyvinyl alcohol (QPVA) via dual cross-linking through annealing treatment and condensation reaction to restrain the membrane water swelling. The Wu% of QPVA membrane could be reduced to 22.87±0.81%. Due to the hydrophilia (59.86±0.21°), negative ζ-potential surface and aliphatic matrix of QPVA, no transition time appeared under our experiment condition, indicating the QPVA membrane was scarcely fouled by SDBS. And the existence of SDBS in dilute solution generated slightly effect on the QPVA membrane resistance and only 7.47±0.21% reduction of the desalination rate in ED process. Furthermore, only distilled water was used as solution or reaction media, without any harmful organic solvents, presenting an environmentally friendly route for the preparation of water-based anion-exchange membrane. So, the excellent anti-fouling performance along with green preparation of QPVA showed its remarkable prospect for desalination purpose in ED process.
Desalination, 2003
The adsorption and transport characteristics of natural organic matter (NOM) in an ion-exchange (IX) membrane were investigated and the various methods to characterize the properties of NOM and the IX membrane were collectively evaluated in this study. NOM adsorption by an IX membrane is affected by both pH and ion strength. Under alkaline pH and low ionic strength, greater NOM adsorption can be expected. A good relationship was obtained between the amount of adsorbed NOM and the zeta potential. The NOM acids constituents are expected to be transported preferentially through an IX membrane during the electrodialysis (ED) process because of their negative charge density. However, the molecular mass of the NOM acids was too high to allow them to pass through the IX membrane pores, and this caused an accumulation or adsorption of the solutes on the membrane surface. A fractional-rejection method was applied to determine the apparent pore size distribution of IX membranes and the selectivity coefficient was used to calculate apparent charges of NOM. The major apparent pore size distribution (PDS) of the IX membrane used in this study lay in the range 100-200 mass units. The apparent charge of the NOM used was 5.5 (dimensionless).
Journal of Membrane Science, 2012
Membrane fouling by organic solutes during electrodialysis is a well-known problem, especially during water treatment. Fouling causes an increase in membrane electrical resistance, leading to shortened membrane life and increased energy consumption. This article describes an improvement to the antifouling potential for an anion exchange membrane (AEM) by surface modification with poly-(sodium 4-styrene sulfonate) (PSS). The antifouling potential of the AEM was evaluated by the transition time, i.e. the time elapsed before the fouling took place, using sodium dodecylbenzene sulfonate (SDBS) as a model organic foulant. It was shown that the antifouling potential of the AEM was considerably improved by surface modification with PSS. A mechanism for fouling by SDBS is also theoretically discussed and it is concluded that adsorption of SDBS micelles on the AEM surface was prevented by surface modification with PSS and the antifouling potential was improved because both hydrophilicity and the negative charge density were increased on the modified membrane surface. Additionally, it was confirmed that surface modification with PSS scarcely affects the performance of AEM during electrodialysis.