# Making Drinking Water from Saltwater with Shock Electrodialysis

 Producing fresh water from saltwater, or cleaning up producer water from drilling and wastewater operations remain a key sector in the mining, and manufacturing industry Desalination Infinity Turbine is currently working on the development of incorporating Teflon with SDR (Spinning Disc Reactor) technology to implement a commercial scale shock electrodialysis process (a recently developed electrokinetic process, which can be used to continuously desalinate artificial seawater). Problem: Conventional desalination technologies such as distillation and reverse osmosis are well suited for the supply of fresh water at large scale. The expensive infrastructure and high capital, operating, and maintenance costs associated with these technologies, however, limit their application in remote or underdeveloped areas. Concept: Infinity is working within its developed technologies to utilize the amazing qualities of Teflon, static electricity, and cavitation (sonochemistry) to further promote simple low cost solutions for removing salt from water.
 Infinity Turbine spinning disc technology includes pumping, expanding, cavitation, and more SHOCK-ELECTRODIALYSIS Electrodialysis (ED), which has been commercially exploited for 70 years now, is another water treatment method, using selective transport of ionic species in an electric field across ion-exchange membranes [5]. This process offers high energy efficiency for desalination in the range of concentrations between ca. 500 and 5000 ppm and is, therefore, more suitable for low-salinity brackish waters. Thanks to being able to selectively separate charged species from non-ionic ones, ED finds use in the treatment of industrial wastewaters, including removal and recycling of heavy metals (nickel) from rinse waters, inorganic acid regeneration in the chemical industry, reacidification of fruit juices, desalination of whey in the food industry, and more. On the other hand, the effectiveness of ED falls significantly as the feed stream becomes more diluted (<100 ppm). The high ohmic resistivity drives the energy consumption up. Therefore, ED cannot be used for complete water purification purposes. In electrodeionization (EDI), a related method, this is solved by filling the dilute chambers with ion-exchange beads. Ion-exchangers are characterized by relatively high conductivity and provide a large active ion-exchange area. As a result, it is possible to obtain a concentration of ionic and ionizable species far below ppb levels. Therefore, EDI is a method that is used in the electronic, pharmaceutical, and chemical industries, where ultra-pure water with conductivity lower than 0.1 μs/cm is needed.Conventional desalination technologies such as distillation and reverse osmosis are well suited for the supply of fresh water at large scale. The expensive infrastructure and high capital, operating, and maintenance costs associated with these technologies, however, limit their application in remote or underdeveloped areas. Here, we show that shock electrodialysis, a recently developed electrokinetic process, can be used to continuously de- salinate artificial seawater (3.5 wt. percent) for small-scale (less than 25 m3 day−1 as a long-term goal), decentralized applications. In two steps, 99.8 percent of the salt fed was rejected, with selectivity for magnesium ions of which > 99.99 percent were removed (based on measurements of concentration by mass spectrometry). We also demonstrated for the first time the viability of using and continuously recycling solutions of sodium citrate buffer to simultaneously reduce waste and inhibit precipitation reactions in the electrode streams. As with conventional electrodialysis, the energy consumed by our technology can be significantly reduced by desalinating sources that are less saline than seawater, such as brackish water and various industrial or municipal process streams. Since the design of the system and choice of materials have yet to be optimized, there remain ample opportunities to further reduce the cost of desalination by shock electrodialysis.Scalable and Continuous Water Deionization by Shock Electrodialysis Theory of shock electrodialysis I: Water dissociation and electrosmotic vortices Shock electrodialysis (shock ED), an emerging electrokinetic process for water purification, leverages the new physics of deionization shock waves in porous media. In previous work, a simple leaky membrane model with surface conduction can explain the propagation of deionization shocks in a shock ED system, but it cannot quantitatively predict the deionization and conductance (which determines the energy consumption), and it cannot explain the selective removal of ions in experiments. This two-part series of work establishes a more comprehensive model for shock ED, which applies to multicomponent electrolytes and any electrical double layer thickness, captures the phenomena of electroosmosis, diffusioosmosis, and water dissociation, and incorporates more realistic boundary conditions. In this paper, we will present the model details and show that hydronium transport and electroosmotic vortices (at the inlet and outlet) play important roles in determining the deionization and conductance in shock ED. We also find that the results are quantitatively consistent with experimental data in the literature. Finally, the model is used to investigate design strategies for scale up and optimization.Water Purification by Shock Electrodialysis: Deionization, Filtration, Separation, and Disinfection [ We show that shock ED can thoroughly filter micron-scale particles and aggregates of nanoparticles present in the feedwater. We also demonstrate that shock ED can enable disinfection of feedwaters, as approximately 99% of vi- able bacteria (here Escherichia coli) in the inflow were killed or removed by our prototype. Shock ED also sepa- rates positive from negative particles, contrary to claims that ICP acts as a virtual barrier for all charged particles. By combining these functionalities (filtration, separation and disinfection) with deionization, shock ED has the potential to enable highly compact and efficient water purification systems. ] The development of energy and infrastructure efficient water purification systems are among the most critical engineering challenges facing our society. Water purification is often a multi-step process involving filtration, desalination, and disinfection of a feedstream. Shock electrodialysis (shock ED) is a newly developed technique for water desalination, leveraging the formation of ion concentration polarization (ICP) zones and deionization shock waves in microscale pores near to an ion selective element. While shock ED has been demonstrated as an effective water desalination tool, we here present evidence of other simultaneous functionalities. We show that, unlike electrodialysis, shock ED can thoroughly filter micron-scale particles and aggregates of nanoparticles present in the feedwater. We also demonstrate that shock ED can enable disinfection of feedwaters, as approximately $99\%$ of viable bacteria (here \textit{E. coli}) in the inflow were killed or removed by our prototype. Shock ED also separates positive from negative particles, contrary to claims that ICP acts as a virtual barrier for all charged particles. By combining these functionalities (filtration, separation and disinfection) with deionization, shock ED has the potential to enable more compact and efficient water purification systems.Theory of shock electrodialysis I: Water dissociation and electrosmotic vortices [ Shock electrodialysis (shock ED), an emerging electrokinetic process for water purification, leverages the new physics of deionization shock waves in porous media. ] Shock electrodialysis (shock ED), an emerging electrokinetic process for water purification, leverages the new physics of deionization shock waves in porous media. In previous work, a simple leaky membrane model with surface conduction can explain the propagation of deionization shocks in a shock ED system, but it cannot quantitatively predict the deionization and conductance (which determines the energy consumption), and it cannot explain the selective removal of ions in experiments. This two-part series of work establishes a more comprehensive model for shock ED, which applies to multicomponent electrolytes and any electrical double layer thickness, captures the phenomena of electroosmosis, diffusioosmosis, and water dissociation, and incorporates more realistic boundary conditions. In this paper, we will present the model details and show that hydronium transport and electroosmotic vortices (at the inlet and outlet) play important roles in determining the deionization and conductance in shock ED. We also find that the results are quantitatively consistent with experimental data in the literature. Finally, the model is used to investigate design strategies for scale up and optimization.Shock Electrodialysis for Water Purification andElectrostatic Correlations in Simple andPolyelectrolytes Desalination systems have become an important part of many water supply networks and they have also been considered as solutions for water shortages and in areas in which access to clean and safe water is still a problem. The range of available water that is encountered in these situations tends to be quite large, ranging from seawater to just slightly brackish water to even just water with trace amounts of toxic ions or small amounts of infectious bacteria or viral particles. While current technologies provide a very good solution to desalinating seawater via reverse osmosis, the solutions that are currently used for brackish water or contaminated water are often suboptimal in that they are often inefficient in this operating regime and that it is also often difficult to deploy these systems in environments with little infrastructure.In this thesis, shock electrodialysis is proposed and examined for its potential to ef- fectively providing a solution for use with brackish water but especially contaminated water. Shock electrodialysis is in many ways related to electrodialysis, but it is based on the emerging science of desalination shocks in porous media, giving it the distinct advantage of using fewer membranes and separating fresh and brine stream via a non-physical barrier (i.e. the shock), which then also allows for removal of particles. Furthermore, in contrast to electrodialysis, it is able to completely deionize water, which is extremely important when dealing with water sources that are contaminated with traces of toxic ions. Experimental results from a proof-of-concept prototype are presented and compared with numerical and analytical modeling result with the aim to better understand the important factors in shock electrodialysis. These results suggest that, while shock electrodialysis can indeed fully deionize water, the energy efficiency is currently still very low and needs to be significantly improved before this technology can be effectively employed in the field.In addition to shock electrodialysis, this thesis also explores the use of a 4th-order Poisson equation to include ion-ion correlations in a simple manner when modeling two different systems. The first system considered is a surface that was coated with a polyelectrolyte together in solution with a simple electrolyte of various concentration, which is of interest because as the concentration varies, inversion of the apparentdifference in potential between this surface and a bare surface is found to occur, a phenomenon that is not explained by traditional models. The second system con- sidered is simply an electrolyte in which the aim was to improve the Debye-Huckel theory for ionic activity to be able to more accurately predict the activity using a very simple model. In both system, correlations proved to be important to varying degrees and the 4th-order equation proved to be useful better predicting the observed phenomena.Water purification by shock electrodialysis: Deionization, filtration, separation, and disinfection The development of energy and infrastructure efficient water purification systems is among the most critical en- gineering challenges facing our society. Water purification is often a multi-step process involving filtration, desa- lination, and disinfection of a feedstream. Shock electrodialysis (shock ED) is a newly developed technique for water desalination, leveraging the formation of ion concentration polarization (ICP) zones and deionization shock waves in microscale pores near to an ion selective element. While shock ED has been demonstrated as an effective water desalination tool, we here present evidence of other simultaneous functionalities. We show that shock ED can thoroughly filter micron-scale particles and aggregates of nanoparticles present in the feedwater. We also demonstrate that shock ED can enable disinfection of feedwaters, as approximately 99% of vi- able bacteria (here Escherichia coli) in the inflow were killed or removed by our prototype. Shock ED also sepa- rates positive from negative particles, contrary to claims that ICP acts as a virtual barrier for all charged particles. By combining these functionalities (filtration, separation and disinfection) with deionization, shock ED has the potential to enable highly compact and efficient water purification systems.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.Small-scale desalination of seawater by shock electrodialysis onventional desalination technologies such as distillation and reverse osmosis are well suited for the supply of fresh water at large scale. The expensive infrastructure and high capital, operating, and maintenance costs associated with these technologies, however, limit their application in remote or underdeveloped areas. Here, we show that shock electrodialysis, a recently developed electrokinetic process, can be used to continuously de- salinate artificial seawater (3.5 wt. %) for small-scale (≤ 25 m3 day−1 as a long-term goal), decentralized ap- plications. In two steps, 99.8% of the salt fed was rejected, with selectivity for magnesium ions of which > 99.99% were removed (based on measurements of concentration by mass spectrometry). We also demonstrated for the first time the viability of using and continuously recycling solutions of sodium citrate buffer to si- multaneously reduce waste and inhibit precipitation reactions in the electrode streams. As with conventional electrodialysis, the energy consumed by our technology can be significantly reduced by desalinating sources that are less saline than seawater, such as brackish water and various industrial or municipal process streams. Since the design of the system and choice of materials have yet to be optimized, there remain ample opportunities to further reduce the cost of desalination by shock electrodialysis.Optimizing porous material in shock electrodialysis unit Shock electrodialysis (SED) is a new electromembrane process for water desalination. The principle is similar to electrodeionization – the product should be ultrapure water, but the inlet water can be the same quality as the inlet to electrodialysis. The ion exchange resin is substituted by porous media and used ion exchange membranes are just of one type (i.e., two cation exchange membranes or two anion exchange membranes). The use of porous media is essential. Many physical and chem- ical phenomena including electroosmotic flow, electroconvection, surface conduction combined in the moment lead to the phenomena of a “–shock wave” and SED, respectively. The mechanism of the wave is represented by the formation of a sharp border in the water stream between the highly concentrated and ion-free zone. The whole process was studied by Prof. Martin Bazant’s group at MIT, Department of Chemical Engineering. The aim of this particular study is characterization and experimental testing of porous material as an essential component of SED. A variety of organic and synthetic porous materials were tested by various analytical methods and in the SED laboratory unit itself. The work reports an overview of commonly available and appropriate materials analogous to the glass frit used in the first prototypes developed by Bazant’s group. Considering the physi- cal properties and behavior in experimental conditions and based on the results exhibiting stable desalination, we suggest the optimal porous material as well as the housing for this media. Finally, it is represented by quality of products, hydrodynamic resistance, prize of the porous material, availability and also by workability (machinability) for appropriate shape and also construction stability.Water desalination with a single-layer MoS2 nanopore [ In conclusion, we have shown that MoS2 membranes are promising for water purification and salt rejection. ] Efficient desalination of water continues to be a problem facing the society. Advances in nanotechnology have led to the development of a variety of nanoporous membranes for water purification. Here we show, by performing molecular dynamics simulations, that a nanopore in a single-layer molybdenum disulfide can effectively reject ions and allow transport of water at a high rate. More than 88 percent of ions are rejected by membranes having pore areas ranging from 20 to 60 A2. Water flux is found to be two to five orders of magnitude greater than that of other known nanoporous membranes. Pore chemistry is shown to play a significant role in modulating the water flux. Pores with only molybdenum atoms on their edges lead to higher fluxes, which are ∼70% greater than that of graphene nanopores. These observations are explained by permeation coefficients, energy barriers, water density and velocity distributions in the pores.Here we demonstrate that a single-layer MoS2 can effectively separate ions from water. Using molecular dynamics simulations, we investigate water desalination in MoS2 as a function of pore size, chemistry, geometry and applied hydrostatic pressure.Electrodialytic Processes: Market Overview, Membrane Phenomena, Recent Developments and Sustainable Strategies [ The quality of the water that people drink, the food they eat and the environment in which they live is the most important factor affecting human health. ] In the context of preserving and improving human health, electrodialytic processes are very promising perspectives. Indeed, they allow the treatment of water, preservation of food products, production of bioactive compounds, extraction of organic acids, and recovery of energy from natural and wastewaters without major environmental impact. Hence, the aim of the present review is to give a global portrait of the most recent developments in electrodialytic membrane phenomena and their uses in sustainable strategies. It has appeared that new knowledge on pulsed electric fields, electroconvective vortices, overlimiting conditions and reversal modes as well as recent demonstrations of their applications are currently boosting the interest for electrodialytic processes. However, the hurdles are still high when dealing with scale-ups and real-life conditions. Furthermore, looking at the recent research trends, potable water and wastewater treatment as well as the production of value-added bioactive products in a circular economy will probably be the main applications to be developed and improved. All these processes, taking into account their principles and specificities, can be used for specific eco-efficient applications. However, to prove the sustainability of such process strategies, more life cycle assessments will be necessary to convince people of the merits of coupling these technologies.Overlimiting Current and Shock Electrodialysis in Porous Media Most electrochemical processes, such as electrodialysis, are limited by diffusion, but in porous media, surface conduction and electroosmotic flow also contribute to ionic flux. In this article, we report experimental evidence for surface-driven overlimiting current (faster than diffusion) and deionization shocks (propagating salt removal) in a porous medium. The apparatus consists of a silica glass frit (1 mm thick with a 500 nm mean pore size) in an aqueous electrolyte (CuSO4 or AgNO3) passing ionic current from a reservoir to a cation-selective membrane (Nafion). The current−voltage relation of the whole system is consistent with a proposed theory based on the electroosmotic flow mechanism over a broad range of reservoir salt concentrations (0.1 mM to 1.0 M) after accounting for (Cu) electrode polarization and pH-regulated silica charge. Above the limiting current, deionized water (≈10 μM) can be continuously extracted from the frit, which implies the existence of a stable shock propagating against the flow, bordering a depleted region that extends more than 0.5 mm across the outlet. The results suggest the feasibility of shock electrodialysis as a new approach to water desalination and other electrochemical separations.Electrodialysis for water desalination: a critical assessment of recent developments on process fundamentals, models and applications The need for unconventional sources of fresh water is pushing a fast development of desalination technologies, which proved to be able to face and solve the problem of water scarcity in many dry areas of the planet. Membrane desalination technologies are nowadays leading the market and, among these, electrodialysis (ED) plays an important role, especially for brackish water desalination, thanks to its robustness, extreme flexibility and broad range of applications. In fact, many ED-related processes have been presented, based on the use of Ion Exchange Membranes (IEMs), which are significantly boosting the development of ED-related technologies. This paper presents the fundamentals of the ED process and its main developments. An important outlook is given to operational aspects, hydrodynamics and mass transport phenomena, with an extensive review of literature studies focusing on theoretical or experimental characterisation of the complex phenomena occurring in electromembrane processes and of proposed strategies for process performance enhancement. An overview of process modelling tools is provided, pointing out capabilities and limitations of the different approaches and their possible application to optimisation analysis and perspective developments of ED technology. Finally, the most recent applications of ED-related processes are presented, highlighting limitations and potentialities in the water and energy industry.Spinning Disc Reactor to produce Nanoparticles: Applications and Best Operating Variables A spinning disc reactor (SDR) is a useful equipment to produce monodisperse nanoparticles with controllable properties, as particle size and particle size distribution. Since the late 90s, this technology has been successfully proven for the reaction and solvent-antisolvent precipitation process. This paper reviews the works on the use of SDR to produce inorganic and organic compounds. Firstly, the more significant works on the subject are presented concerning the produced compound, then the factors influencing the process performances are examined in the light of the results in the literature. Finally, some considerations on the fluid stream's hydrodynamics modelling along the disc surface are attempted.Textile Wastewater Treatment on a Spinning Disc Reactor: Characteristics, Performances,and Empirical Modeling Spinning disc (SD) technology has been successfully applied, for the first time, in real textile wastewater treatment with no other additional processing. The SD efficiency was investigated using real textile effluents to study the color and suspended solids removals at different effluent-supplying flowrates (10–30 L/h) and different disc rotational speeds (100–1500 rpm) with good experimental results; thus, it can minimize the polluting loads within a short time period. Furthermore, within this study, process modeling and its classical optimization were applied to SD technology for wastewater treatment. The experiments were organized according to an active central composite rotatable 23 order design, considering as independent variables the wastewater flowrate, rotational speed, and operating time and, as optimization criteria, the suspended solids removal and discoloration degree. Overall, this novel study proved that the SD technology applied in textile effluent treatment is a suitable alternative to a primary mechanical step.Reaction engineering and hydrodynamics of a rotor-stator spinning disc reactor In this thesis, an RSSDR was investigated in terms of reaction engineering and hy- drodynamics, by means of studying the heat transfer properties via an experimental and a numerical approach. The latter involved the simulation of the flow behavior in the regarded reactor gap, before simulating the conjugate heat transfer of an RSSDR model. Moreover, the potential of the regarded RSSDR for intensification of a strongly exothermic reaction involving mixing of two immiscible fluids, i.e., the epoxidation of methyl oleate (MO) with hydrogen peroxide and formic acid, was studied. Shock-Electrodialysis Publications
 Vertical SDR spinning disc reactor from Infinity Turbine Electrodialysis Electrodialysis (ED), which has been commercially exploited for 70 years now, is another water treatment method, using selective transport of ionic species in an electric field across ion-exchange membranes [5]. This process offers high energy efficiency for desalination in the range of concentrations between ca. 500 and 5000 ppm and is, therefore, more suitable for low-salinity brackish waters. Thanks to being able to selectively separate charged species from non-ionic ones, ED finds use in the treatment of industrial wastewaters, including removal and recycling of heavy metals (nickel) from rinse waters, inorganic acid regeneration in the chemical industry, reacidification of fruit juices, desalination of whey in the food industry, and more. On the other hand, the effectivity of ED falls significantly as the feed stream becomes more diluted (<100 ppm). The high ohmic resistivity drives the energy consumption up. Therefore, ED cannot be used for complete water purification purposes. In electrodeionization (EDI), a related method, this is solved by filling the dilute chambers with ion-exchange beads. Ion-exchangers are characterized by relatively high conductivity and provide a large active ion-exchange area. As a result, it is possible to obtain a concentration of ionic and ionizable species far below ppb levels. Therefore, EDI is a method that is used in the electronic, pharmaceutical, and chemical industries, where ultra-pure water with conductivity lower than 0.1 μs/cm is needed.Conventional desalination technologies such as distillation and reverse osmosis are well suited for the supply of fresh water at large scale. The expensive infrastructure and high capital, operating, and maintenance costs associated with these technologies, however, limit their application in remote or underdeveloped areas. We also demonstrated for the first time the viability of using and continuously recycling solutions of sodium citrate buffer to simultaneously reduce waste and inhibit precipitation reactions in the electrode streams. As with conventional electrodialysis, the energy consumed by our technology can be significantly reduced by desalinating sources that are less saline than seawater, such as brackish water and various industrial or municipal process streams. Since the design of the system and choice of materials have yet to be optimized, there remain ample opportunities to further reduce the cost of desalination by shock electrodialysis. Shock-Electrodialysis Publications
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