Electrodeionization Process Research Articles

Performance evaluation of resin wafer electrodeionization for enhanced nitrogen recovery from ammonium-containing water environment

Ammonium ion (NH4+) is a common pollutant from various sources like human and animal waste, industrial effluents, agricultural runoff, and commercial products, with traditional treatment methods often generating secondary contaminants, such as nitrite and nitrate. In this study, an energy-efficient resin-wafer electrodeionization (RW-EDI) process was employed for nitrogen recovery from ammonium-rich water. The system was operated in a continuous mode, with voltage-current curve measurements identifying a limiting current density of 2.2 A cm−2. With the NH4+ concentration of 1 g/L and a flow rate of 2.4 mL min−1, the system was tested at various cell voltages (1.2–7.2 V). The system could achieve 80 % NH4+ removal efficiency at a cell voltage of 3 V, current density of 2.2 A cm−2, influent NH4+ level of 3 g/L, and flow rate of 6.4 mL min−1. The observed current efficiency and the calculated power consumption were 41 % and 0.78 kWh m−3, respectively. Finally, a mass balance model was developed to predict the number of RW-EDI stacks for complete removal of NH4+ from the feed. Overall, the result from this study demonstrates that the RW-EDI-based system could be a promising technology for recovering nitrogen from wastewater.

Characteristics of nutrient element migration in electrodeionization process

In this work, a constructed five-compartment electrodeionization (EDI) device was used to treat simulated wastewater with ammonium and phosphate ions. The voltage and influent concentration in the EDI system were examined. Meanwhile, the ion migration characteristics in the EDI were studied. Results showed that at optimal conditions, operating at 15 V, with an ammonia nitrogen concentration of 1500 mg/L, and a phosphate concentration of 300 mg/L, the removal rates of ammonia nitrogen and phosphate were 98.50 % and 73.85 %, respectively. The energy consumption of ammonia and phosphorus was 1.347 kWh/mol and 43.629 kWh/mol. The ion migration characteristic experiments revealed that adsorption and desorption rates of the resin do not impose limitations on ion migration in EDI; the ion migration in EDI device is mainly through the resin phase and the rate of ion migration is intricately influenced by the concentration of nutrient ions present on the resin.

Deduction of carbon footprint for membrane desalination processes towards carbon neutrality: A case study on electrodeionization for ultrapure water preparation

Decarbonization of the industrial sector, especially in power generation, is vital for achieving carbon neutrality. The life-cycle greenhouse gas (GHG) emissions, namely carbon footprint, of a technology under the decarbonizing macro-environment should be deduced to reveal further opportunities for GHG reduction. Herein, a case study on ultrapure water (UPW) preparation by electrodeionization (EDI) was investigated through life cycle assessment (LCA) and compared with a conventional mixed-bed ion exchange (MBIX) technology. The carbon footprint of the EDI process was quantified as 1.30 kg CO2-eq/metric ton UPW, which is 27.73 % lower than the MBIX. With a decarbonized power grid and recycling of wasted EDI modules, the carbon footprint will be reduced by 91 %. Meanwhile, the proportion of module production and waste management will increase to 18 %. Thus, we suggest reducing the process energy consumption and improving the current efficiency of the EDI process by process modeling and optimization. With the decarbonization of electricity, the degraded reuse of plastic and the recycling of ion-exchange membranes and resins could be considered. The application of LCA to quantify the carbon footprint and provide suggestions for low-carbon designs could be extended to membrane desalination or industrial processes, supporting the revolution towards carbon neutrality.

Research on the Ammonia Removal from Synthetic Wastewater by Electrodialysis and Electrodeionization

In this work, the technical capabilities of lab-scale electrodialysis (ED) and the electrodeionization (EDI) processes on removing ammonia from synthetic wastewater were investigated. The overall performance of ED and EDI process in the removal of ammonia from high ammonia concentration synthetic wastewater was assessed by applied electric potential, feed concentration, and energy consumption. Under the conditions of working electric potential, ED showed that ammonia concentration could be reduced from 1,000 to 309 mg/L with a best removal efficiency of 69.1%, EDI showed that the ammonia concentration could be reduced from 1,000 to 120.9 mg/L with a best removal efficiency of 87.91%, the energy consumption of ED and EDI were in the range of 1.7–12.96 Wh/L and 6.2–149.2 Wh/L, respectively. Under the conditions of feed concentration, ED and EDI obtained a best removal efficiency of 57.93% and 98.5%, respectively, the energy consumption was in the range of 9.36–53.55 Wh/L and 62.7–218.1 Wh/L, respectively, excessive applied electric potential and concentration will lower current efficiency and increase energy consumption. The ammonia removal efficiency of EDI was found to be higher than ED, but the current efficiency of EDI was lower than ED, and the stack current of EDI increased quickly under constant voltage when the feed concentration was over 1,000 mg/L. The results showed that EDI was suitable for low concentration solution treatment, whereas ED was suitable for high concentration solution treatment. As a novel technology of groundwater contamination treatment, the process was proved to be feasible and provided foundation for further research.

Modeling and optimization of electrodeionization process for the energy-saving of ultrapure water production

Electrodeionization (EDI) is essential for producing ultrapure water in power plants and high-tech industries. Compared with the traditional ion exchange process, EDI does not require high-pollution resin regeneration by acid and alkali reagents. However, the process is markedly energy-intensive, and thus it is crucial to reduce the energy consumption. The reduction may be achieved by optimizing the operating conditions and module design. Previous mathematical models of the EDI process have been based on the mass transfer mechanism of ion removal. However, the water dissociation reactions, which are crucial for the energy efficiency of ion removal and thus EDI optimization, have rarely been considered. In particular, the design of EDI modules has not been studied. In this study, the water dissociation reactions in the EDI model were considered to simulate the ion removal process and energy consumption. In addition, the design variables of the equipment configuration and the operating conditions of an industrial-scale EDI module were optimized to reduce the energy consumption via nonlinear programming. The results show that the energy consumption of the current industrial EDI operation can be reduced by 22.4% when only the operating conditions are optimized. Furthermore, the optimization of the design and operation, based on the annual cost, will lead to a 50.4% decrease in the annual cost. The developed modeling and optimization method will play a critical role in an energy-saving operation and low-cost design of the EDI process.

IMPACT OF CONCENTRATION POLARIZATION ON THE EFFICIENCY OF ELECTROMEMBRANE DEMINERALIZATION OF SUGAR SYRUP

The article presents the results of investigation the phenomenon of concentration polarization.
 The technological parameters of electrodialysis and electrodeionization processes at various applied voltages are presented. The results about the influence of concentration polarization on the efficiency of the electromembrane demineralization process of sugar syrup were concluded.

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.

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.

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.

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.

3D Modelling of the Transport Phenomena in a Parallel-Plate Electrodeionization Reactor through CFD

CFD has been used as a useful tool for the description of the phenomena occurring in electrochemical reactors. The present research studies the electrodeionization process from a 3D perspective, coupling the convection, diffusion and migration phenomena involved in the electrodeionization process using COMSOL Multiphysics and a validation of the simulation process is obtained using Digital Image Analysis and Electrodeionization experiments. The used reactor is a parallel plate reactor, previously used for an electrodialysis process with good results, the total volume of each of the 4 compartments ( one for diluted-treated solution, one for the concentrated-waste solution and two electrodic rinses to close the electrical circuit) is of about 19.2 mL. The diluted compartment is filled with IRA-67 ion exchange resin ( 0.5-0.75 mm of diameter) previously conditioned and hydrated. The treated solution is a 20 ppm fluoride solution from NaF and was pumped into de diluted and concentrated compartments at a velocity that allowed a one minute Time of Residence. The simulation was carried out with a 3D model of the reactor using its real measures, only the diluted and concentrated compartments were modelled. The flow of the solution in the concentrated compartment was considered as laminar and in the diluted compartment ( filled with ion exchange resin) a Brinkman-Darcy condition was applied. Nerst-Planck equations were used to describe the transport of the ionic species in the compartments and the flow through a ion exchange membrane. The results show a good flow distribution,as well as a good ion transport. The simulations, confirmed the experimental results. The analized data is very similar in flow distribution and mass transport in the compartments. The results were analized in a quantitative and qualitative form. The validation of this simulated results will allow the improvement of some problematic zones in the reactor and the methodology developed can be useful to other electrochemical reactors.

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.

Effect of ion exchange membrane on the removal efficiency of continuous electrodeionization (CEDI) during low level radioactive wastewater treatment

The treatment of low level radioactive wastewater (LLRW) has gained more attention with the development of nuclear energy. Continuous electrodeionization (CEDI) process is a promising technology to remove trace nuclides and minimize radioactive wastes. In this study, seven CEDI stacks filled with different ion exchange membranes (IEM) were compared for their performance during the LLRW treatment. The removal ratios of boron ranged from 5% to 16%, and the decontamination factors (DF) of nuclides ranged from 15 to 960. The performance of the CEDI stacks varied from each other. Some stacks had high removal efficiencies on both boron and nuclides, while some had high DF values of nuclides but low removal ratio of boron. Correlation analysis showed that ion exchange capacity of IEMs had no significant correlation with the efficiency of CEDI stacks. The diffusion dialysis coefficient had a negative effect on the removal of nuclides, but had no significant effects on the removal of boron. The transport of strong electrolyte nuclides and weak electrolyte boric acid was quite different, which helps to guide the CEDI stack design for different purposes, such as the separation of boron and nuclides or removal them simultaneously.

Development of a Resin Wafer Electrodeionization Process for Impaired Water Desalination with High Energy Efficiency and Productivity

Use of groundwater, reclaimed water, and other impaired water sources is a critical strategy for fresh surface water conservation. Because impaired water desalination by reverse osmosis is energy-intensive, a robust ion-exchange resin wafer electrodeionization technology was developed to conserve energy during impaired water desalination. The loose ion-exchange resin beads were immobilized and molded to form a porous resin wafer material and utilized for impaired water desalination. In this study, the impaired water desalination using resin wafer electrodeionization was evaluated along with various key performance indicators, including current efficiency, energy efficiency, and productivity. Results suggest that resin wafer electrodeionization can improve energy efficiency to >35% in comparison to that of reverse osmosis (normally ∼12%) for impaired water desalination. The energy consumption of resin wafer electrodeionization was found to be 0.354–0.657 kWh/m3 with a productivity of 20.1–41.3 L h–1 m–2 (i...

Optimization of the electrodeionization process: comparison of different resin bed configurations

Optimization of the electrodeionization process: comparison of different resin bed configurations

Application of Electrodeionization Process for Bioproduct Recovery and CO2 Capture and Storage

Application of Electrodeionization Process for Bioproduct Recovery and CO2 Capture and Storage

Simultaneous removal of nitrate and hardness ions from groundwater using electrodeionization

Abstract Nitrate concentrations in groundwater frequently exceed permissible levels for potable water in intensive agricultural regions. It is critical to develop highly efficient techniques for the removal of nitrate at low cost, without the addition of chemicals. In this study, we report on an advanced and efficient approach, referred to as electrodeionization (EDI), for effectively removing and concentrating nitrate with low energy consumption. An additional merit of this process was that hardness ions, such as Ca 2+ and Mg 2+ , were also simultaneously removed from the dilute compartment and recovered in concentrate compartment. Furthermore, the limiting current was systematically investigated and the impacts of different applied currents, water flow rates, and ratios of cationic and anionic exchange resins on the performance of nitrate removal were studied. When treating actual groundwater samples, the EDI system exhibited an excellent removal rate for all ions (>90%) under a low and constant cell voltage. The results confirmed that the EDI process is suitable for the continuous and highly efficacious removal and recovery of nitrate and hardness ions in ground water.

Production of high purity water using membrane-free electrodeionization with improved resin layer structure

Abstract A novel membrane-free electrodeionization (MFEDI) process has been proposed and tested successfully for high purity water production in our previous work. However, to prevent the ions backward migration, the electrode polarity had to be reversed during regeneration, which complicated the regeneration process, reduced the regeneration efficiency and shortened the electrode life. In order to avoid the electrode polarity reversal and enhance the regeneration efficiency, the resin layer structure and the types of mixed resins were changed in this work to form a MFEDI without electrode polarity reversal which was then tested by desalinating the synthetic two-pass RO permeate of seawater with a total of 40 operational cycles. Results demonstrated that the backward migration of Na + ions was prevented effectively; the weak-type resins facilitated the water dissociation and promoted the regeneration of strong-type resins significantly. Both good purification and effective regeneration were achieved. The conductivity of effluent was 0.060–0.063 μS/cm only. The energy consumption and the water recovery were 0.24 kW h/m 3 water and 96.1%, respectively. Repetitive experimental results showed this MFEDI system could work stably.

Evaluating the effectiveness of ion exchangers for the electrodeionization process

A method for the evaluating the performance of ion exchange resins in the electrodeionization process has been proposed. This method is based on the study of the ion exchange kinetics and involves experimental determination of three parameters: the particle size distribution, the ion-exchange capacity, and ion exchange rate constants. Using these parameters, ionic conductivity has been calculated, the value of which has been used for estimating the effectiveness of ion exchangers. Fourteen brands of cation exchange resins have been studied using the proposed procedure. It has been shown that the best grades are lightly crosslinked Amberlyst BD20 and Amberlyst 131WET. In addition, the “granulate”, a potential ion exchange packing for use in electrodeionization, composed of the ion exchange resin by 60% has been investigated. The rate of ion exchange on the best granulate sample has appeared to be 12 times lower than that on the best ion exchange resins.