Electrodeionization Research Articles

Selective removal of Hg2+/As3+/5+ from water system using Suaeda maritima plant based bio-adsorbent hybrid electro-deionization process

Heavy metal pollution is a critical environmental issue to provide safe potable water. Here, we prepared bio-adsorbent (PC@PN) by blending of phytochelatins (PCs) (derived from Suaeda maritima (L.) Dumort plant) in poly(acrylonitrile) (PN). We report bio-adsorbent hybrid electro-deionization (EDI) for the selective removal of Hg2+/As3+/5+ in aqueous medium, and in-situ regeneration of adsorbent by using water-splitting process. EDI process effectively reduced the Hg2+/As3+/5+ concentration from 100 ppb to < 1.0 ppb, while Na+ (present in natural water system) was partial removed (500 ppm to 200–300 ppm). Interestingly, removal efficiency of Hg2+/As3+/5+ was close to 100%, while < 50% removal of Cd2+, and Pb2+ were observed under similar conditions. Quite low energy requirement (1.02–1.53 kWh/kg) corresponding to about 90% current efficiency, revealed the sustainability of the process. In addition, adsorbent exhibited high regeneration up to 60 cycles of experiments, without any significant performance deterioration. The EDI process with bio-adsorbent is promising for selective trace removal of ionic toxicants from the water system.

Proposing an Ultrapure Water Unit Coupled to an Existing Reverse Osmosis Desalination Plant and its Exergy Analysis

In this study, three desalination exergy analysis models including the Cerci et al. model (Model A), Drioli et al. model (Model B) and electrolyte solution model (Model C), were developed on an existing reverse osmosis (RO) desalination plant in Oman (Plant ALG). A modified ultrapure water (UPW) unit fed by Plant ALG has also been proposed (Plant A) based on the technology used in a UPW unit operated under the climate of Europe and fed by European river water (Plant B). The most suitable exergy model for characterizing the proposed UPW production plant was used. Model C was found to be the most proper model among its counterparts. It reflected the electrolytic behavior of the relevant streams and considered as the appropriate model. The major exergy destruction sites were also identified, and the exergy efficiency was calculated. The electro-de-ionization (EDI) and the RO unit were the highest exergy destructive components in Plant A.

Removal of manganese (II) from aqueous solution by ionic liquid impregnated polymeric sorbent and electrodeionization (EDI) techniques

Manganese is an element that is essential for the proper functioning of humans and animals, as it is needed for the functioning of many cellular enzymes. However, overexposure to this metal can be toxic to many organ systems and at various stages of life. In this work, ionic liquid impregnated polymeric sorbent (ILIS) and electrodeionization (EDI) processes were used to remove manganese (Mn2+) from aqueous solutions. The removal of Mn2+ by ILIS is pH dependent and maximum removal is achieved at pH 9. The sorption of Mn2+ on ILIS reached equilibrium in 20 min. For Mn2+ removal by EDI, the applied potential, feed flow rate and H2SO4 concentration in the electrode compartment were optimized. When the applied potential and feed flow rate were increased, the Mn2+ concentration in the feed solution decreased. Varying the H2SO4 concentration in the electrode compartment did not result in differences in the removal rate. The largest calculated flux for Mn2+ is 6.92 × 10−5 mol/m2s, and the mass transfer coefficient is 8.16 × 10−4 m/s. In the last phase of the experiment, ILIS-EDI hybrid techniques were used for the removal of Mn2+. In this case, more than 99.9% was removed from the solution.

(Invited) Continuous Low-Cost Separation of Multivalent Ions from Dilute Aqueous Solutions by Shock Electrodialysis

Shock electrodialysis (SED) is an emerging separations technology, which opens new possibilities for purification, valorization and recycling of contaminated water. By exploiting novel electrokinetic transport phenomena, SED is able to achieve highly selective, continuous ionic separations that are not possible with other electrochemical methods based on ion adsorption in porous electrodes, such as electro-swing adsorption (ESA) and capacitive deionization (CDI), or ion exchange in membrans (alone), such as its cousins, electrodialysis (ED) and electro-deionization (EDI). Instead, the separation in SED is achieved by a steady deionization shockwave in cross flow, which results from the passage of over-limiting current (faster than diffusion) through a charged porous medium, sandwiched between ion-exchange membranes. This talk will introduce the basic principles and mathematical theory of SED, focusing on the separation of trace multivalent from excess monovalent ionic species. Experimental examples include the separation of lead from drinking water and radioactive contaminants from nuclear wastewater. Similar SED systems could be designed to separate valuable ionic species from mining effluents or industrial recycling streams, especially if combined with ESA, CDI, or other electrochemical methods.

Study on the process of simultaneous desalting and boron removal from seawater

Two new combined technologies, reverse osmosis (RO) + electrodeionization (EDI) and reverse osmosis (RO) + ion exchange (IE), were studied for simultaneous desalination and boron removal of seawater. The results show that the RO system has excellent desalination performance under the experimental conditions, and can provide stable desalination rate for the subsequent processes of the two combined schemes. The boron concentration in water has little effect on the desalination rate of RO system, and the boron removal rate of RO system is between 47% and 50%, which provides a good early treatment for the subsequent process. The blank experiment shows that the salinity has little effect on the boron removal rate of RO-EDI equipment, and the boron removal rate is more than 93%, which has excellent and stable boron removal performance, but the water yield of RO-EDI equipment is low (less than 60%). The RO-IE system has a high water yield (> 70%), but the equipment has poor adaptability to influent boron concentration and salinity. The results of effluent water show that the boron concentration of raw water by RO-EDI combined process can be adapted to a wider range, and the influence of salinity is less. Considering comprehensively, RO-EDI process has more advantages and broad application prospects.

Removal of boron by boron selective resin-filled electrodeionization

Boron exists in the earth’s crust mainly in the form of borates or boric acid. Boric acid is a weak electrolyte and does not completely dissociate in aqueous solutions. Due to such features, it is not always possible to remove it efficiently by conventional water treatment technologies. In this work, it is the first time of the usage of boron selective resin-filled electrodeionization (EDI) to remove boron from aqueous solutions. While the experiments were carried out in constant voltage mode, however it was revealed that the applied potential and feed flow rate have significant effects on boron removal. On the other hand, variation in the electrolyte conductivity did not result in any notable changes in the boron removal efficiency. The removal performance of the boron selective resin-filled EDI cell was evaluated by calculation of flux, mass transfer coefficient, and power consumption. The results demonstrated that the feed flow rate has a significant effect on the mass transfer coefficient and flux of boron. The mass transfer coefficient of boron is found to be 7.78 × 10−4m∕s which is much higher than previously reported values in the literature. The energy consumption of boron selective resin-filled-EDI was in the range of 6.64 × 10−3–1.11 × 10 −1 Wh/g. The boron concentration in the solution decreased from 5 mg/L to 0.3 mg/L with a boron removal rate up to 94%.

Electrodeionization of Organic Acids Using Porous Bipolar Resin Wafers

Organic acids are valuable precursors for synthesizing specialty chemicals and monomers for bio-degradable plastics. These chemicals often originate in complex bio-oil and fermentation mixtures making capture of these species challenging. This talk presents material innovations of the porous ion-exchange resin wafers used in electrodeionization (EDI) for targeted removal and purification of organic acids. The new porous conductors consisted of anion- or cation-exchange resins that were immobilized in a wafer format with anion- or cation-exchange ionomer binders. The adoption of ionomer binders over the conventional polyethylene binder enhanced ionic conductivity of the resin wafers. Interestingly, differences in ionic conductivity between the porous anion and cation resin wafers were ascribed to the ratio of ionic mobility values of the counterions they transferred. With the new materials in-hand, single anion and cation-conducting resin wafers were appended together with a water dissociation catalyst at the interface. These layered resin wafers constituted a Janus bipolar resin wafer; and when deployed in EDI, they were able to raise the diluate stream’s pH value by 3 to 4 units while also removing other anions. Raising the pH above the pKA of organic acids ionizes these species making them susceptible for transport under applied electric fields and purification in resin-wafer EDI. Overall, the new porous, Janus bipolar resin wafers are promising materials for extracting organic acids from liquid streams that have a low concentration of total dissolved solids (i.e., other ionic species). Figure 1

Desalination Performance Assessment of Scalable, Multi-Stack Ready Shock Electrodialysis Unit Utilizing Anion-Exchange Membranes.

Incumbent electromembrane separation processes, including electrodialysis (ED) and electrodeionization (EDI), provide competitive techniques for desalination, selective separation, and unique solutions for ultra-pure water production. However, most of these common electrochemical systems are limited by concentration polarization and the necessity for multistep raw water pre-treatment. Shock electrodialysis (SED) utilizes overlimiting current to produce fresh, deionized water in a single step process by extending ion depleted zones that propagate through a porous medium as a sharp concentration gradient or a shock wave. So far, SED has been demonstrated on small scale laboratory units using cation-exchange membranes. In this work, we present a scalable and multi-stack ready unit with a large, 5000 mm2 membrane active area designed and constructed at the Technical University of Liberec in cooperation with MemBrain s.r.o. and Mega a.s. companies (Czechia). We report more than 99% salt rejection using anion-exchange membranes, depending on a dimensionless parameter that scales the constant applied current by the limiting current. It is shown that these parameters are most probably associated with pore size and porous media chemistry. Further design changes need to be done to the separator, the porous medium, and other functional elements to improve the functionality and energy efficiency.

Current Research Trends and the Need for Localization in Ultrapure Water Production Facilities in Semiconductor Industries

Objectives : This study aims to summarize the market status, patent applications, and technology trends for the production of ultrapure water in semiconductor industries. In addition, the potential of technological localization of ultrapure water production facility is reviewed in order to incubate domestic core technologies as well as to reduce the technical dependence to the market stake holders.Methods : Through the collection and summary of information from global water institute (GWI), market analyst firms in ultrapure water fields, and the patent analysis for the past 10 years, the technological gap between domestic and market leading in Japan, the United States, and Europe were analyzed. In addition, the research trend related to the core removal processes for the production of ultrapure water was also analyzed.Results and Discussion : As a result of market analysis in the industrial water sector, the capital investment is expected to reach USD 39.9 billion by 2024, with a steady growth of 4.1% per year. The unit processes required for the production of ultrapure water becomes more complex and diversified, and the recent technological advancement has been mainly put on the development of eco-friendly water treatment processes such as electrodeionization (EDI) in order to reduce the chemical usage. In addition, research on the development of new processes for the treatment of hardly degradable trace substances (i.e. urea, THM, IPA, etc.) is actively under investigation. However, the patent analysis revealed that the three Japanese companies occupied 71% of the world’s patents on the ultrapure water production.Conclusions : In ultrapure water production technology, the design of unit processes is important, and the design of a system that combines and arranges unit processes is the core technology. Thus, the incubation of domestic companies that have ability to design the array of unit processes for ultrapure water production is necessary for the localization of ultrapure water technology. However, although a few companies have completed the commercialization of core technologies, there is lack of the test field to evaluate the long-term performance of products. Therefore, for the development of domestic technologies in the ultrapure water production, it is necessary to construct a test-bed capable of evaluating the performance of domestic products. In addition, it is expected that localization of ultrapure water production technology will be facilitated with the participation of consumers.

The relationship between the pH value of dilute effluent streams and system durability in the separate bed electrodeionization process

The successful application of electrodeionization (EDI) for the preparation of ultra-pure water has been encouraging researchers to explore its feasibility in the treatment of heavy metal electroplating wastewaters. Based on the separate bed membrane stack, the relationship between the pH of dilute effluent streams and its long-term operation stability was investigated. The pH, conductivity, electric current and voltage were recorded on-line with cupric ions contents measured off-line. The microstructure and morphology of ion exchange resins and membranes were studied with infrared spectroscopy and scanning electron microscopy. It is the adsorption saturation in the cation exchange resins-filled compartment (CR-cell) that results in the acidity of dilute effluent waters due to the consumption of hydroxide ions in the anion exchange resins-filled compartment (AR-cell). The periodic change of acidity and alkalinity of dilute effluents was caused by the alternative processes of adsorption saturation and hydrolysis regeneration in CR-cell. The conversion of quaternary amines into tertiary ones of the anion resins and membranes owing to hygro-thermal aging weakened alkaline and shortened the acid-base change period. Increasing stack voltage and intermittent leaching play an important role in prolonging the service life of EDI, and make it feasible to remove heavy metal ions from industrial wastewaters.

Use of response surface methodology for optimization of thorium(IV) removal from aqueous solutions by electrodeionization (EDI)

In this research, the thorium(IV) removal from the aqueous solution was conducted by electrodeionization (EDI). Thorium(IV) removal experiments with EDI are designed using RSM based on CCD, and three independent variables were scrutinized, including applied voltage (X1), flow rate (X2), and thorium(IV) concentration (X3). A quadratic model with R2 equal to 0.9825 was the best model for the analysis of variance, which was in a good agreement with experimental results. The X1X2 did have a significant effect, and other interactions had an insignificant effect. The optimal values of voltage, flow rate, and thorium(IV) concentration were obtained 9.8 V, 3.4 mL min−1, and 63.1 mg L−1, respectively. In these conditions, the thorium(IV) removal was 99.06%, which was 0.31% different from the software prediction. The EDI efficiency was evaluated by calculating the current efficiency, mass flux and mass transfer coefficient. The results showed that the flow rate increment has a more significant effect on the increase of the mass flux and mass transfer coefficient than the impact of the voltage increases. Thorium(IV) removal with different resin configuration was as follow: layered < mixed < only cationic resin. EDI and electrodialysis comparisons showed that with EDI, thorium(IV) removal increased by more than 35%. Through this study, the desirable removal of thorium(IV) was achieved by EDI.

Advancing electrodeionization with conductive ionomer binders that immobilize ion-exchange resin particles into porous wafer substrates

Electrodeionization (EDI) is an electrically driven separations technology that employs ion-exchange membranes and resin particles. Deionization occurs under the influence of an applied electric field, facilitating continuous regeneration of the resins and supplementing ionic conductivity. While EDI is commercially used for ultrapure water production, material innovation is required for improving desalination performance and energy efficiency for treating alternative water supplies. This work reports a new class of ion-exchange resin-wafers (RWs) fabricated with ion-conductive binders that exhibit exceptional ionic conductivities—a 3–5-fold improvement over conventional RWs that contain a non-ionic polyethylene binder. Incorporation into an EDI stack (RW-EDI) resulted in an increased desalination rate and reduced energy expenditure compared to the conventional RWs. The water-splitting phenomenon was also investigated in the RW in an external experimental setup in this work. Overall, this work demonstrates that ohmic resistances can be substantially curtailed with ionomer binder RWs at dilute salt concentrations.

Microscale electrodeionization: In situ concentration profiling and flow visualization

Electrodeionization (EDI) is membrane-based desalination utilizing ion exchange membranes and ion exchange resins. By combining Electrodialysis and Ion exchanger, EDI can produce ultrapure water in a continuous-flow manner. Although its theoretical mechanisms are well documented, there is no experimental platform that can provide microscopic details inside of the system. In this paper, we present microscale EDI that can visualize in situ ion concentration, pH, and fluid flows. The platform was fabricated by filling ion exchange resins as a monolayer in a transparent polydimethylsiloxane channel between cation and anion exchange membranes. According to operating voltages (0–15V), distinct behaviors of ion concentration profile, pH shift, and fluid flows were observed in Ohmic, limiting, and overlimiting regimes. It is noteworthy that overlimiting regimes can be sub-categorized as water-splitting and electroconvection regimes. In the early stage (4–8V), water-splitting is dominant with pH change near the membranes and resins; under a higher voltage (8–15V), electroconvection starts to occur even water-splitting tries to suppress the development of the extended space charge layer and corresponding electroconvective instability. Accelerated ionic migration by electroconvection can improve current efficiency up to 80%. This is a clear departure from overlimiting dynamics in electrodialysis (with electroconvection only), ion exchanger (with no distinct regime), and even from that in previous EDI experiments (with water splitting only).

A deep desalination and anti-scaling electrodeionization (EDI) process for high purity water preparation

Electrodeionization (EDI) is a composite desalination process that combines ion exchange and electrodialysis to achieve continuous deionization. However, the current EDI technology has demanding requirements for the feed water, and fouling in the stack often exists in practical industrial applications. For the above-mentioned issue, a novel deep desalination and anti-scaling EDI stack configuration was proposed. Different from previous configuration, a cation exchange membrane was added to the right side of the reverse anode exchange membrane to form a protective chamber, in which mixed bed ion exchange resin was filled with a certain proportion, Meanwhile, the influent of concentrated stream was supplied by dilute stream. Aiming at no fouling and maximum dilute water resistivity, the effect of operating conditions on the EDI process for the preparation of high purity water were studied. All the results demonstrated that for the feed water with a hardness of 7.9 mg·L−1 (calculated as CaCO3), with the proposed EDI stack configuration and a membrane stack voltage of 8 V, a concentrated flux of 6 L/h, a dilute flux of 32 L/h, the membrane stack can run stably for 400 h without fouling, and the dilute water resistivity can reach 16.1 MΩ·cm−1, the total desalination rate was 99.8%, the hardness ion removal rate was close to 100%, the energy consumption could be maintained at <0.03 KWh·m3. These results indicate that the proposed EDI stack configuration can broaden the limits of EDI feed water conditions and it is of great practical significance to realize the industrial application of the deep desalination and anti-scaling EDI model.

In-sight studies on concentration polarization and water splitting during electro-deionization for rapid production of ultrapure water (@18.2 MΩ cm) with improved efficiency

We report in-sight studies on concentration polarization and water splitting, responsible for in-situ regeneration of ion-exchange resin during electro-deionization (EDI) without any use of acid/base. Herein, we introduced rapid EDI (REDI) with high productivity of ultrapure water (resistivity: 18.2 MΩ cm). The effect of membrane surface charge concentration on EDI performance was broadly investigated for cation-exchange membranes (CEMs) with 1.2–4.7 × 10−5 mol cm−3 surface charge concentrations. In these cases, well-commercialized interpolymer anion-exchange membrane (IP-AEM) was used. Resin wafers, in place of loose resin, avoids several difficulties during EDI such as inconsistent performance, unequal fluid flow distribution, draining of resin with flow stream, etc. Using CEM with high surface charge concentration, energy consumption was significantly reduced, while energy efficiency and productivity were improved. EDI process with highly charged CEM (SPS-62) showed 0.85 kWh m−3 energy consumption, 0.13 m h−1 productivity and 81.3% current efficiency. After several ED experiments, ion-exchange capacity (IEC) of resin was unaltered, which ensured the in-situ resin regeneration and longevity of process.

Combined ultrafiltration and electrodeionization techniques for microbial xylitol purification

Oil palm empty fruit bunch (OPEFB) is biomass waste from crude palm oil industry that can be utilized for xylitol production. In recent years, xylitol production is dominated by a microbial fermentation method where the fermentation product contains many impurities, thus requires further purification and separation processes. In this work, ultrafiltration (UF) and electrodeionization (EDI) membranes were used for purification of xylitol from either model solution or OPEFB hydrolysate that has been fermented by Debaromyces hansenii. First, the optimum conditions for purification of xylitol from xylose, acetic acid, and salts in model solution using EDI were evaluated. The results showed that the optimum current density, concentrate flow rate, and diluate flow rate was found to be 22.5A/m2, 0.4m/s, and 0.5m/s, respectively. Meanwhile, validation experiment using the OPEFB hydrolysate fermentation broth showed that UF-EDI membrane configuration was able to remove 99% of microorganism and biomass, 99% pigment, >46% of xylose, and >99% ionic impurities including >90% acetic acid with a loss of xylitol about 30–50%.

Pure Water Production Technology By Electrodeionization Method In Dark Factories Scope

Nowadays we talk about Dark factories, IOT and Industry 4,0. Together with these concept, every step for “Dark Auxiliary Facilities” is getting big importance. High purity water, which is needed by many industrial plants, especially energy, chemical, pharmaceutical and electronics, can now be produced with fully electrical energy without the need for chemical regeneration by acid and caustic thanks to the Electrodeionization (EDI) technology instead of the classical “Miksbed resin” systems. EDI system in the future is the candidate to be a "Dark auxiliary facilities" equipment. It is environmental friendly and has cost advantages. In this report, we mentioned the points of use the Electrodeionization technology in industry.

Preparation and Characterization of Monovalent Cation Selective Membranes Prepared by a Layer-By-Layer Pore-Filled Technique

Membrane fouling is one of fatal barriers in electrochemical water treating technologies using ion exchange membranes (IEM) such as electrodeionization (EDI), Electrodialysis (ED), capacitive deionization (CDI), and reverse electrodialysis (RED). Calcium and Magnesium ions are representative foulants which make cake-like scale on the IEMs, leading to high resistance and low durability. In order to minimize membrane fouling in systems using IEMs, we are having developed monovalent cation selective membranes prepared by a layer-by-layer pore-filled technique. Anion exchangeable electrolytes are pore-filled on both surfaces of a semi-pore-filled cation exchange membrane (layer-by-layer). A porous PE substrate (<20 um) is used to be filled with electrolytes and crosslinking agents and to be polymerized. Monovalent cation selectivity against divalent ions, calcium and magnesium ions, of the resulting membranes was evaluated using 1N MgCl2, CaCl2 and NaCl solutions.

Characterization of Ion Exchange Material Behavior under Pressure Simulating Electro-Membrane Cell Conditions

Goal of this work was to measure dimensional changes of ion-exchange membranes and resins used in electrodialysis (ED) or electrodeionization (EDI) devices under the applied pressure and temperatures up to 60 °C in order to describe their behavior in real conditions of these processes. Regarding ion exchange resins, measurements of their compressibility were carried out with samples of gel strongly basic and strongly acidic pure resins, their mixture and macroporous strongly acidic resin. In case of ion exchange membranes, their thickness changes under the influence of pressure and temperature were measured and long-term experiments were performed with the maximal applied pressure. To obtain a complete view, ED spacer frame foil properties were also examined in long-term experiments. For each experiment, the unique work methodology and measurement apparatus was proposed. It was found that each resin exhibited specific behavior under applied pressure and temperature. Furthermore, the important impact of temperature changes on ion exchange membranes and ED spacer foils was observed, and then, it was examined under the conditions of pressure load similar to that in real ED device. This work confirms that the research of mechanical properties of ion exchange materials has a great importance, mainly if it simulates real conditions in industrial ED and EDI modules. It can help in designing new or improved module components taking into account expected temperature or pressure changes of ion exchange materials.

Effect of operational conditions on post-treatment of RO permeate of geothermal water by using electrodeionization (EDI) method

With the growing of electronics, semiconductors, food and pharmaceutical manufactures, the need of water quantity with high purity is increasing. The water quality needed should be with high electrical resistance and free of weakly ionized dissolved species. Integration of separation processes such as reverse osmosis (RO) and electrodeionization (EDI) was proven to be successful to produce water with high quality. This paper is about the applicability of EDI method for post-treatment of RO permeate of geothermal water. For this purpose, the effects of process parameters such as feed flow rate, electrical potential applied, type of ion exchange membranes, and cell number on reduction of electrical conductivity and the contents of boron, silicon and arsenic in EDI product water were investigated. In addition, pseudo first order and pseudo second order kinetics models, infinitive solution volume (ISV) and unreacted core (UCM) models were applied to determine the rate controlling steps of the removal of electrical conductivity and boron by EDI process. Obtained results revealed that a EDI product water containing ˂0.20mg B/L, ˂0.05mg Si/L and ˂0.10μg As/L was produced using a multi-cell EDI in which ion exchange resins in mixed bed configuration is placed between Neosepta CMX-AMX ion exchange membrane pair. These results were obtained when the optimum flow rate of 1.08L/h and electrical potential of 20V were applied to multi-cell EDI. At the optimal operational conditions, boron removal was found to be governed by second order kinetic model and the determining steps were film diffusion and liquid film according to ISV and UCM models, respectively. It was observed that thick ion exchange membranes were better than thin ion exchange membranes for polishing RO permeate of geothermal water by using EDI process.