Electrochemical Regeneration of Spent Alkaline Absorbent from Direct Air Capture
Shu, Qingdian ; Legrand, Louis ; Kuntke, Philipp ; Tedesco, Michele ; Hamelers, Hubertus V.M. - \ 2020
Environmental Science and Technology 54 (2020)14. - ISSN 0013-936X - p. 8990 - 8998.
CO2 capture from the atmosphere (or direct air capture) is widely recognized as a promising solution to reach negative emissions, and technologies using alkaline solutions as absorbent have already been demonstrated on a full scale. In the conventional temperature swing process, the subsequent regeneration of the alkaline solution is highly energy-demanding. In this study, we experimentally demonstrate simultaneous solvent regeneration and CO2 desorption in a continuous system using a H2-recycling electrochemical cell. A pH gradient is created in the electrochemical cell so that CO2 is desorbed at a low pH, while an alkaline capture solution (NaOH) is regenerated at high pH. By testing the cell under different working conditions, we experimentally achieved CO2 desorption with an energy consumption of 374 kJ·mol-1 CO2 and a CO2 purity higher than 95%. Moreover, our theoretical calculations show that a minimum energy consumption of 164 kJ·mol-1 CO2 could be achieved. Overall, the H2-recycling electrochemical cell allowed us to accomplish the simultaneous desorption of high-purity CO2 stream and regeneration of up to 59% of the CO2 capture capacity of the absorbent. These results are promising toward the upscaling of an energy-effective process for direct air capture.
Exploiting Donnan Dialysis to enhance ammonia recovery in an electrochemical system
Rodrigues, Mariana ; Sleutels, Tom ; Kuntke, Philipp ; Hoekstra, Douwe ; Heijne, Annemiek ter; Buisman, Cees J.N. ; Hamelers, Hubertus V.M. - \ 2020
Chemical Engineering Journal 395 (2020). - ISSN 1385-8947
Ammonia recovery - Donnan dialysis - Electrochemical system
A hydrogen recycling electrochemical system (HRES) can be used for energy efficient removal of TAN (Total ammonia nitrogen, ammonium and ammonia) from wastewater. When a current is applied, a concentration gradient of cations builds up between catholyte and feed solution. When no current is applied, cations (Na+ and K+) diffuse back to the feed solution from the catholyte as a result of the concentration difference. These cations will be exchanged for other cations (NH4 + and H+) to maintain electroneutrality: a phenomenon known as Donnan Dialysis. In this study, Donnan Dialysis was explored as a strategy to enhance the TAN removal efficiency in an HRES. In continuous operation, Donnan Dialysis did not clearly affect TAN removal efficiency. In batch operation, Donnan Dialysis resulted in (10 ± 2) % higher removal efficiency compared to operation without Donnan Dialysis. By analyzing transport numbers of the different cations, we show that in batch mode, Donnan Dialysis indeed exchanges mostly NH4 + with Na+ and K+. In continuous mode, however, more protons were transported from anode to cathode. Batch operation with Donnan Dialysis achieved similar removal to continuous operation but consumed less energy (between 7.8 kJ gN −1 and 10.1 kJ gN −1) than continuous operation. Donnan Dialysis can be a good strategy to enhance TAN recovery in batch operation mode since additional ammonium was removed at a lower energy input.
Role of ion exchange membranes and capacitive electrodes in membrane capacitive deionization (MCDI) for CO2 capture
Legrand, L. ; Shu, Q. ; Tedesco, M. ; Dykstra, J.E. ; Hamelers, H.V.M. - \ 2020
Journal of Colloid and Interface Science 564 (2020). - ISSN 0021-9797 - p. 478 - 490.
Carbon electrodes - Donnan model - Electrochemical carbon capture - MCDI
Recently we showed that membrane capacitive deionization (MCDI) can be used to capture CO2, but we found that the performance decreases with decreasing current density. In the present study, we investigate the effect of electrodes and ion exchange membranes by performing experiments with two membranes (CO2-MCDI), with one membrane (cation or anion exchange membrane), and without membranes (CO2-CDI). We find that the anion exchange membrane is essential to keep high CO2 absorption efficiencies (Λa=nCO2(g)/ncharge), while the absorption efficiency of the CO2-CDI cell was lower than expected (Λa≈0.5 for CO2-MCDI against Λa≈0.18 for CO2-CDI). Moreover, we theoretically investigate ion adsorption mechanisms in the electrodes by comparing experimental data of a CO2-CDI cell with theoretical results of the classic amphoteric-Donnan model developed for conventional CDI. By comparing the experimental results with the amph-D model, we find that the model overestimates the absorption efficiency in CO2-CDI experiments. To understand this discrepancy, we investigate the effects of other phenomena, i.e., (i) low ion concentration, (ii) passive CO2 absorption, and (iii) the effect of acid-base reactions on the chemical surface charge.
Theory of Ion and Electron Transport Coupled with Biochemical Conversions in an Electroactive Biofilm
Lichtervelde, A.C.L. De; Heijne, A. Ter; Hamelers, H.V.M. ; Biesheuvel, P.M. ; Dykstra, J.E. - \ 2019
Physical Review Applied 12 (2019)1. - ISSN 2331-7019
An electroactive biofilm is a porous layer of bacteria covering an electrode, which plays an important role in bioelectrochemical systems, such as in the microbial fuel cell. We derive a dynamic model of ion transport, biochemical reactions, and electron transport inside such a biofilm. After validating the model against data, we evaluate model output to obtain an understanding of the transport of ions and electrons through a current-producing biofilm. For a system fed with a typical wastewater stream containing organic molecules and producing 5 A m−2, our model predicts that transport of the organic molecules is not a limiting factor. However, the pH deep within the biofilm drops significantly, which can inhibit current production of such biofilms. Our results suggest that the electronic conductivity of the biofilm does not limit charge transport significantly, even for a biofilm as thick as 100 μm. Our study provides an example of how physics-based modeling helps to understand complex coupled processes in bioelectrochemical systems.
Electrical energy from CO2 emissions by direct gas feeding in capacitive cells
Legrand, L. ; Schaetzle, O. ; Tedesco, M. ; Hamelers, H.V.M. - \ 2019
Electrochimica Acta 319 (2019). - ISSN 0013-4686 - p. 264 - 276.
Capacitive cell - Capacitive deionization - CO - Membrane potential - Mixing energy
This work demonstrates the possibility to harvest electrical power from CO2 emissions by feeding CO2 and air gas directly into a capacitive cell. Hamelers et al. previously showed, that the available mixing energy of CO2 emitted into the air can be converted into electricity, but at high energy costs for gas-sparging in the process. In the present work, electrical power is generated by feeding the gas directly into the capacitive cell. We investigated three different cell designs (namely, “conventional”, “flow-by(wire)”, and “flow-by(flat)”), by changing both electrode and cell geometry. The flow-by(flat), inspired from fuel cell design, showed the best performance thanks to a high membrane potential (≈190 mV), which is the highest value so far reported from CO2 and air. A maximum membrane permselectivity between CO2 and air of 90% was obtained, i.e., almost double of values reported in previous studies. On the contrary, the “conventional” cell design gave poor performance due to non-optimal gas flow in the cell. We highlight the importance of water management and internal electrical resistance, to indicate directions for future developments of the technology.
The RED Fouling Monitor : A novel tool for fouling analysis
Bodner, E.J. ; Saakes, M. ; Sleutels, T. ; Buisman, C.J.N. ; Hamelers, H.V.M. - \ 2019
Journal of Membrane Science 570-571 (2019). - ISSN 0376-7388 - p. 294 - 302.
Fouling analysis - Ion-exchange membranes - Organic fouling - RED Fouling Monitor - Salinity gradient
RED is a technology for harvesting energy using the salinity gradient between river (RW) and seawater (SW). Membrane fouling can decrease the net power density. Fouling inhibition might be indispensable. For implementing antifouling strategies more detailed insights upon fouling are required. In RED stacks investigations of single membranes are practically impossible. We introduce the RED Fouling Monitor, in which one side of a single ion-exchange membrane in contact to a foulant-containing feed stream can be studied under OCV and current conditions. Fouling is detectable in four configurations: (1) SW/AEM, (2) RW/AEM, (3) SW/CEM and (4) RW/CEM. Functionality is provided by a novel flow-through salt bridge enabling ionic connection and the incorporation of reference electrodes in close proximity to the membrane surface. The results indicate a stable, reproducible performance under un-fouled conditions. Upon SDBS exposure RW/AEM fouling showed a more pronounced fouling response than SW/AEM fouling. Fouling is partly attributable to the current density and the current field direction. An irreversible, internal fouling of the AEM is indicated when exposed to SDBS in SW. RW/AEM fouling shows to be reversible. With prospect to future systematic investigations this tool can be used to test various configurational, operational designs, different pre-treatment schemes and the fouling potential of feed streams at different seasons. This will result in valuable insights for new constructional sites for future RED plants.
Solvent-Free CO2 Capture Using Membrane Capacitive Deionization
Legrand, L. ; Schaetzle, O. ; Kler, R.C.F. De; Hamelers, H.V.M. - \ 2018
Environmental Science and Technology 52 (2018)16. - ISSN 0013-936X - p. 9478 - 9485.
Capture of CO2, originating from both fossil fuels, such as coal combustion, and from renewables, such as biogas, appears to be one of the greatest technological challenges of this century. In this study, we show that membrane capacitive deionization (MCDI) can be used to capture CO2 as bicarbonate and carbonate ions produced from the reaction of CO2 with water. This novel approach allows capturing CO2 at room temperature and atmospheric pressure without the use of chemicals. In this process, the adsorption and desorption of bicarbonate ions from the deionized water solution drive the CO2(g) absorption-desorption from the gas phase. In this work, the effects of the current density and the CO2 partial pressure were studied. We found that between 55 and 75% of the electrical charge of the capacitive electrodes can be directly used to absorb CO2 gas. The energy requirement of such a system was found to be ∼40 kJ mol-1 at 15% CO2 and could be further improved by reducing the ohmic and non-ohmic energy losses of the MCDI cell.
Energy-Efficient Ammonia Recovery in an Up-Scaled Hydrogen Gas Recycling Electrochemical System
Kuntke, Philipp ; Rodrigues, Mariana ; Sleutels, Tom ; Saakes, Michel ; Hamelers, Hubertus V.M. ; Buisman, Cees J.N. - \ 2018
ACS sustainable chemistry & engineering 6 (2018)6. - ISSN 2168-0485 - p. 7638 - 7644.
Ammonia recovery - Electrochemical system - Hydrogen recycling - Up-scaling
Nutrient and energy recovery is becoming more important for a sustainable future. Recently, we developed a hydrogen gas recycling electrochemical system (HRES) which combines a cation exchange membrane (CEM) and a gas-permeable hydrophobic membrane for ammonia recovery. This allowed for energy-efficient ammonia recovery, since hydrogen gas produced at the cathode was oxidized at the anode. Here, we successfully up-scaled and optimized this HRES for ammonia recovery. The electrode surface area was increased to 0.04 m2 to treat up to 11.5 L/day (∼46 gN/day) of synthetic urine. The system was operated stably for 108 days at current densities of 20, 50, and 100 A/m2. Compared to our previous prototype, this new cell design reduced the anode overpotential and ionic losses, while the use of an additional membrane reduced the ion transport losses. Overall, this reduced the required energy input from 56.3 kJ/gN (15.6 kW h/kgN) at 50 A/m2 (prototype) to 23.4 kJ/gN (6.5 kW h/kgN) at 100 A/m2 (this work). At 100 A/m2, an average recovery of 58% and a TAN (total ammonia nitrogen) removal rate of 598 gN/(m2 day) were obtained across the CEM. The TAN recovery was limited by TAN transport from the feed to concentrate compartment.
Concentration Gradient Flow Batteries : salinity gradient energy systems as environmentally benign largescale electricity storage
Egmond, Willem Johannes van - \ 2018
Wageningen University. Promotor(en): C.J.N. Buisman, co-promotor(en): H.V.M. Hamelers. - Wageningen : Wageningen University - ISBN 9789463438421 - 160
The total amount of energy derived from wind turbines and solar panels is rapidly growing. Since these sources of energy are intermittent in nature, supply and demand of energy show an increasing mismatch. To accommodate efficient, large scale use of intermittent renewable energy sources such as wind and sun, energy storage systems are necessary. One of the primary drivers for the increasing use of renewable energy sources is concern about the quality of our environment. Therefore, it is vital that energy storage systems storing sustainable energy, are sustainable themselves. Creating storage systems using abundant, environmentally friendly materials is therefore an important prerequisite for a sustainable energy supply. This thesis aims to explore the potential of the Concentration Gradient Flow Battery (CGFB) as large-scale electricity storage technology. A CGFB stores energy in aqueous solutions of salt (typically NaCl) and uses ion exchange membranes to extract energy from the solutions.
Chapter 1 (Introduction) introduces the need of energy storage. Available energy storage technologies are compared in terms of technical performance but also in terms of safety, environment and political aspects. The CGFB is introduced and explained. Finally, a theoretical background on how a salinity gradient can create a useable voltage across ion exchange membranes is presented.
In Chapter 2 (The Concentration Gradient Flow Battery as electricity storage system: Technology potential and energy dissipation) a working prototype is constructed and tested. This chapter explains how a CGFB works in more detail and the theoretical maximum energy density of the battery is explored (~3.2 kWh m-3 for NaCl). The maximum energy density is shown to vary as function of salt concentrations, volume ratio between salt and fresh solution and salt type. A model is introduced which includes the major dissipation factors; internal resistance, water transport and co-ion transport. Experimental work is performed to validate the model. A wide range of salt concentrations (0-3 m NaCl) and current densities (-49 to +33 A m-2) is chosen. From this work, an optimal working range is identified where the concentrate concentrations preferably do not exceed the 1 m. At higher concentrate concentrations water transport and co-ion transport are found to increase heavily decreasing the energy efficiency of the battery.
In chapter 2 it was shown that the CGFB works best at low (<1 m) concentrations. At low concentrations, internal resistance and water transport are shown to be the most important dissipation factors. In chapter 3 (Energy efficiency of a Concentration Gradient Flow Battery at elevated temperatures), a more specific working range (0-1 m) is explored in more detail. Mass transport is measured accurately and an improved experimental approach allows to determine losses by water transport, internal resistance and co-ion transport in more detail. Chapter 3 shows for both the charge and discharge step the energy efficiency and quantifies the losses at each moment in time. The effect of current density and state-of-charge on power density and energy efficiency is analysed. It is shown that it is not efficient to either completely discharge or charge a CGFB. An optimal working domain is identified (Δm > 0.5 and η > 0.4) where the CGFB delivers best performance in terms of energy efficiency (max. discharge η of 72%) and power density (max. discharge power density, 1.1 W m-2). Tests are also performed at different temperatures (10, 25 and 40 ˚C) to measure the effect of temperature on mass transport, internal resistance and power density. Finally, it is shown that water transport is a major issue in the operation of a CGFB where it causes hysteresis (after discharge the battery does not return to its original state), lower efficiency and leads to decreased energy density.
To improve the performance of a CGFB, it is necessary to decrease water transport across the membranes. Chapter 4 (Tailoring ion exchange membranes to enable low osmotic water transport and energy efficient electrodialysis) introduces modified membranes with a polymer mesh inside with a very small open area (2, 10, 18 and 100% open area). The membranes are prepared by casting an ionomer solution over a polymeric mesh. The material, open area and surface properties of the mesh are changed and the effect on electrical resistance, water transport properties and the efficiency of the charge process are investigated. Comparing a meshed membrane with a homogeneous membrane, the osmotic water transfer coefficient of the meshed membrane is shown to be reduced up to a factor eight. Decreasing the open area of the mesh decreases the water permeability of the membrane but adversely increases electrical resistance. The membranes are tested at different current densities (5-47.5 A m-2). Chapter 4 shows that at low current densities (5-25 A m-2) the meshed membranes outperform the homogeneous membranes in terms of energy efficiency (at a Δc of 0.7 M, maximum energy efficiency η = 67 % for the meshed membranes and η = 50 % for the homogeneous membranes). Also, the meshed membranes outperform the homogeneous membranes in terms of diluate yield across all tested current densities (diluate yield of 78-87% for the meshed membranes, 43-76% for the homogeneous membranes). Using a meshed membrane in a CGFB will lead to less issue with hysteresis. In addition, the relation between material and surface property of the mesh and the ionomer resin is investigated. The type of material (PA or PET) is shown to affect the water permeability of the meshed membrane. It is shown that in some cases, compared to a non-treated mesh, a chemically treated mesh (2 M NaOH treatment) yields lower water permeability membranes. Finally, when optimized ion exchange resin is used it is expected that the water permeability can be reduced even further.
Chapter 2 and chapter 3 show that the CGFB is able to store energy in NaCl solutions which has significant environmental benefits. The measured power density is relatively low and energy density is limited because high concentrations cannot be used. In chapter 5 (Performance of an environmentally benign Acid Base Flow Battery at high energy density) the process is changed to significantly improve power density and energy density while maintaining the environmental benefits. The adjusted system uses three energy storage solutions instead of two and stores most energy in a proton and hydroxyl ion concentration gradient. To create protons and hydroxyl ions (during charge) and to let the ions recombine to pure water again (during discharge) a bipolar membrane is added. Chapter 5 shows that the theoretical maximum energy density of the adjusted system (called Acid Base Flow Battery, ABFB) is over three times higher than the theoretical maximum of the original CGFB (chapter 2, maximum energy density of the CGFB is ~3.2 kWh m-3 and ~11.1 kWh m-3 for the ABFB). In addition, experiments demonstrate that the ABFB reaches a power density which is about a factor four higher compared to the original CGFB (3.7 W m-2 compared to 0.9 W m-2 of membrane area). The main dissipation sources are identified and quantified (energy lost by; co-ion transport 39-65%, ohmic resistance 23-45% and non-ohmic resistance 4-5%). The low selectivity of the membranes to protons and hydroxyls lead to a low coulombic efficiency (13-27 %). The ABFB has potential to be improved significantly. Development of better proton blocking anion exchange membranes and hydroxyl ion blocking cation exchange membranes would increase ABFB performance. Also decreasing the thickness of membranes and compartments would increase ABFB performance as it would lead to lower internal resistance energy losses. In addition, higher current densities would help reduce energy losses by co-ion transport.
Chapter 6 (General discussion and outlook) discusses important aspects of CGFB technology from a societal and commercial point of view. Costs and revenues of energy storage systems are very important drivers and can largely determine the chance of success for a storage technology. First a theoretical background of costs calculations for energy storage systems is presented. Next, the costs of future CGFB systems is calculated and compared to competing technologies. In terms of costs, the ABFB outperforms the CGFB system (0.259 and 0.366 € kWh-1 cycle-1 respectively). Also, possible revenue sources are discussed. Stacking of multiple revenue streams is possible and recommended to increase profitability. Both systems cannot yet generate a profit as costs are too high and single revenue streams are low. However, although difficult, based on the costs calculations, when performance is increased, costs can be reduced and multiple revenue streams are stacked, a commercially viable CGFB/ABFB system is estimated to be feasible. Besides technical and costs aspects, also sustainability of energy storage systems is of major importance. The energy consumption of the production and use of storage systems over their lifetime is analysed and the potential of a CGFB system is discussed. Also, choice in material and system design is discussed. Finally, the size of storage technologies is important. Therefore, the size of a future CGFB system is estimated and discussed with the help of case studies. For diurnal energy storage, the size of a CGFB/ABFB is deemed acceptable given that performance is increased. Seasonal energy storage is not feasible in terms of size without significant technological improvement.
Energy storage with CGFB systems is shown possible. There is a clear need for increased technical performance and reduced costs to create a profitable CGFB. Yet, because of the exciting benefits across different aspects such as safety, environment and politics, CGFB technology is worth continued research.
Performance of an environmentally benign acid base flow battery at high energy density
Egmond, W.J. van; Saakes, M. ; Noor, I. ; Porada, S. ; Buisman, C.J.N. ; Hamelers, H.V.M. - \ 2018
International Journal of Energy Research 42 (2018)4. - ISSN 0363-907X - p. 1524 - 1535.
acid base flow battery - bipolar membrane - co-ion transport - energy efficiency - ion exchange membranes - renewable energy storage - sustainable materials
An increasing fraction of energy is generated by intermittent sources such as wind and sun. A straightforward solution to keep the electricity grid reliable is the connection of large-scale electricity storage to this grid. Current battery storage technologies, while providing promising energy and power densities, suffer from a large environmental footprint, safety issues, and technological challenges. In this paper, the acid base flow battery is re-established as an environmental friendly means of storing electricity using electrolyte consisting of NaCl salt. To achieve a high specific energy, we have performed charge and discharge cycles over the entire pH range (0–14) at several current densities. We demonstrate stable performance at high energy density (2.9 Wh L−1). Main energy dissipation occurs by unwanted proton and hydroxyl ion transport and leads to low coulombic efficiencies (13%–27%).
(Bio)electrochemical ammonia recovery : progress and perspectives
Kuntke, P. ; Sleutels, T.H.J.A. ; Rodríguez Arredondo, M. ; Georg, S. ; Barbosa, S.G. ; Heijne, A. Ter; Hamelers, Hubertus V.M. ; Buisman, C.J.N. - \ 2018
Applied Microbiology and Biotechnology 102 (2018)9. - ISSN 0175-7598 - p. 3865 - 3878.
Ammonia recovery - Bioelectrochemical systems - Electrochemical systems - Total ammonia nitrogen - Wastewater treatment
In recent years, (bio)electrochemical systems (B)ES have emerged as an energy efficient alternative for the recovery of TAN (total ammonia nitrogen, including ammonia and ammonium) from wastewater. In these systems, TAN is removed or concentrated from the wastewater under the influence of an electrical current and transported to the cathode. Subsequently, it can be removed or recovered through stripping, chemisorption, or forward osmosis. A crucial parameter that determines the energy required to recover TAN is the load ratio: the ratio between TAN loading and applied current. For electrochemical TAN recovery, an energy input is required, while in bioelectrochemical recovery, electric energy can be recovered together with TAN. Bioelectrochemical recovery relies on the microbial oxidation of COD for the production of electrons, which drives TAN transport. Here, the state-of-the-art of (bio)electrochemical TAN recovery is described, the performance of (B)ES for TAN recovery is analyzed, the potential of different wastewaters for BES-based TAN recovery is evaluated, the microorganisms found on bioanodes that treat wastewater high in TAN are reported, and the toxic effect of the typical conditions in such systems (e.g., high pH, TAN, and salt concentrations) are described. For future application, toxicity effects for electrochemically active bacteria need better understanding, and the technologies need to be demonstrated on larger scale.
Tailoring ion exchange membranes to enable low osmotic water transport and energy efficient electrodialysis
Porada, S. ; Egmond, W.J. van; Post, J.W. ; Saakes, M. ; Hamelers, H.V.M. - \ 2018
Journal of Membrane Science 552 (2018). - ISSN 0376-7388 - p. 22 - 30.
Electrical resistance - Electrodialysis - Ion exchange membrane - Osmosis - Water desalination
Ion exchange membranes have been applied for water desalination since the 1950s in a process called electrodialysis, ED. Parallel to the transport of ions across ion exchange membranes, water molecules are transported from diluate to concentrate compartments reducing ED efficiency. In this study tailor made meshed membranes were prepared by embedding polymeric meshes with significantly reduced open area into an ion conductive polymer. These membranes were characterized to assess their transport properties. It is shown that by changing mesh open area, material and surface properties, it is possible to significantly reduce osmotic water transport. Polyamide mesh embedded in a cation exchange polymer showed an eightfold decrease of the water mass transport coefficient. Unexpectedly, osmotic water transport was not affected when the same mesh material was embedded in an anion exchange polymer. A decrease of the osmotic water transport for meshed anion exchange membranes was achieved by using a polyethylene terephthalate mesh. Despite the associated electrical resistance increase, application of meshed membranes increased diluate yield and allowed for more energy efficient operation in case ED is confined to a low current density regime.
Membrane Selectivity Determines Energetic Losses for Ion Transport in Bioelectrochemical Systems
Sleutels, Tom H.J.A. ; Heijne, Annemiek ter; Kuntke, Philipp ; Buisman, Cees J.N. ; Hamelers, Hubertus V.M. - \ 2017
ChemistrySelect 2 (2017)12. - ISSN 2365-6549 - p. 3462 - 3470.
BES - ion exchange membrane - MEC - MET - MFC
Ion transport through ion exchange membranes in Bioelectrochemical Systems (BESs) is different from other electrochemical cells as a result of the complex nature of the electrolyte, as the electrolytes in BESs contain many other cations and anions than H + and OH − . Moreover, these other cations and anions are generally present in high concentrations and therefore determine the ion transport through the membrane. In this work, we provide a theoretical framework for understanding ion transport across ion exchange membranes in BESs. We show that the transport of cations and anions other than H + and OH − determines the pH gradient between anode and cathode, and on top of that, also determines the membrane potential. Experimental data for microbial electrolysis cells with cation and anion exchange membranes are used to support the theoretical framework. In case of cation exchange membranes, the total potential loss consists of both the pH gradient and the concentration gradient of other cations, while in case of anion exchange membranes, the total potential loss is lower because part of the pH gradient loss can be recovered at the membrane. The presented work provides a better theoretical understanding of ion transport through ion exchange membranes in general and in BESs specifically.
Hydrogen Gas Recycling for Energy Efficient Ammonia Recovery in Electrochemical Systems
Kuntke, Philipp ; Rodríguez Arredondo, Mariana ; Widyakristi, Laksminarastri ; Heijne, Annemiek ter; Sleutels, Tom H.J.A. ; Hamelers, Hubertus V.M. ; Buisman, Cees J.N. - \ 2017
Environmental Science and Technology 51 (2017)5. - ISSN 0013-936X - p. 3110 - 3116.
Recycling of hydrogen gas (H2) produced at the cathode to the anode in an electrochemical system allows for energy efficient TAN (Total Ammonia Nitrogen) recovery. Using a H2 recycling electrochemical system (HRES) we achieved high TAN transport rates at low energy input. At a current density of 20 A m-2, TAN removal rate from the influent was 151 gN m-2 d-1 at an energy demand of 26.1 kJ gN -1. The maximum TAN transport rate of 335 gN m-2 d-1 was achieved at a current density of 50 A m-2 and an energy demand of 56.3 kJ gN -1. High TAN removal efficiency (73-82%) and recovery (60-73%) were reached in all experiments. Therefore, our HRES is a promising alternative for electrochemical and bioelectrochemical TAN recovery. Advantages are the lower energy input and lower risk of chloride oxidation compared to electrochemical technologies and high rates and independence of organic matter compared to bioelectrochemical systems. (Chemical Equation Presented).
Load ratio determines the ammonia recovery and energy input of an electrochemical system
Rodríguez Arredondo, Mariana ; Kuntke, Philipp ; Heijne, Annemiek Ter; Hamelers, Hubertus V.M. ; Buisman, Cees J.N. - \ 2017
Water Research 111 (2017). - ISSN 0043-1354 - p. 330 - 337.
Complete removal and recovery of total ammonia nitrogen (TAN) from wastewaters in (bio)electrochemical systems has proven to be a challenge. The system performance depends on several factors, such as current density, TAN loading rate and pH. The interdependence among these factors is not well understood yet: insight is needed to achieve maximum ammonium recovery at minimal energy input. The aim of this study was to investigate the influence of current density and TAN loading rate on the recovery efficiency and energy input of an electrochemical cell (EC). We therefore defined the load ratio, which is the ratio between the applied current and the TAN loading rate. The system consisted of an EC coupled to a membrane unit for the recovery of ammonia. Synthetic wastewater, with TAN concentration similar to urine, was used to develop a simple model to predict the system performance based on the load ratio, and urine was later used to evaluate TAN transport in a more complex wastewater. High fluxes (up to 433 gN m−2 d−1) and recovery efficiencies (up to 100%) were obtained. The simple model presented here is also suited to predict the performance of similar systems for TAN recovery, and can be used to optimize their operation.
In-situ carboxylate recovery and simultaneous pH control with tailor-configured bipolar membrane electrodialysis during continuous mixed culture fermentation
Arslan, D. ; Zhang, Y. ; Steinbusch, K.J.J. ; Diels, L. ; Hamelers, Hubertus V.M. ; Buisman, C.J.N. ; Wever, H. de - \ 2017
Separation and Purification Technology 175 (2017). - ISSN 1383-5866 - p. 27 - 35.
Bipolar membrane - Electrodialysis - Fermentation - ISPR - Short chain carboxylates
Anaerobic fermentation of organic waste streams by mixed culture generates a mixture of short chain carboxylic acids. To avoid inhibitory effects of the acids or their consumption in internal conversion reactions in the mixed culture environment, in-situ recovery of acids can be beneficial. In this study, electrodialysis with bipolar membranes (EDBM) was applied to a mixed culture fermentation on organic waste streams using a novel EDBM stack with “direct contact” operation mode. We could demonstrate simultaneous recovery of carboxylates from the fermenter by the EDBM stack while in-situ generation and transport of hydroxyl ions to the fermenter allowed direct pH control. Experiments showed productivity increase after EDBM coupling to the fermenter, and complete elimination of external base consumption. It was also observed that EDBM was able to drive the mixed culture fermentation towards acetate and propionate type of carboxylates.
Energy efficiency of a concentration gradient flow battery at elevated temperatures
Egmond, W.J. van; Starke, U.K. ; Saakes, M. ; Buisman, C.J.N. ; Hamelers, H.V.M. - \ 2017
Journal of Power Sources 340 (2017). - ISSN 0378-7753 - p. 71 - 79.
Aqueous electrolyte - Charge/discharge efficiency - Concentration gradient flow battery - Large scale electricity energy storage - Reverse electrodialysis - Stationary batteries
Fast growth of intermittent renewable energy generation introduces a need for large scale electricity storage. The Concentration Gradient Flow Battery (CGFB) is an emerging technology which combines Electrodialysis with Reverse Electrodialysis into a flow battery which is able to safely store very large amounts of energy in environmental friendly NaCl solutions. In this work, (dis)charge efficiency, energy density and power density are both theoretically and experimentally investigated. Fifteen constant current experiments (−47.5 to +37.5 A m−2) are performed at 40 °C and two experiments (−32.5 and 15 A m−2) at 10 and 25 °C. The magnitudes of the three main energy dissipation sources (internal resistance, water transport and co-ion transport) are measured and mitigation strategies are proposed. The effect of current density, state of charge and temperature on the dissipation sources is analysed. Water transport is shown to cause hysteresis, lower (dis)charge efficiencies and lower energy capacity. At constant current and with increasing temperature, internal resistance is reduced but unwanted water transport is increased. This study reports charge efficiencies up to 58% and discharge efficiencies up to 72%. Full charge or discharge of the battery is shown inefficient. The optimal operating range is therefore introduced and identified (concentration difference Δm > 0.5 and energy efficiency η > 0.4).
On the origin of the membrane potential arising across densely charged ion exchange membranes : How well does the teorell-meyer-sievers theory work?
Galama, A.H. ; Post, J.W. ; Hamelers, H.V.M. ; Nikonenko, V.V. ; Biesheuvel, P.M. - \ 2016
Journal of Membrane Science & Research 2 (2016)3. - ISSN 2476-5406 - p. 128 - 140.
Donnan equilibrium - Ion exchange membranes - Nernst-planck equation - Teorell-meyer-sievers (TMS) theory
A difference in salt concentration in two solutions separated by a membrane leads to an electrical potential difference across the membrane, also without applied current. A literature study is presented on proposed theories for the origin of this membrane potential (Φm). The most well-known theoretical description is Teorell-Meyer-Sievers (TMS) theory, which we analyze and extend. Experimental data for Φm were obtained using a cation exchange membrane (CMX, Neosepta) and NaCl solutions (salt concentration from 1 mM to 5 M). Deviations between theory and experiments are observed, especially at larger salt concentration differences across the membrane. At a certain salt concentration ratio, a maximum in Φm is found, not predicted by the TMS theory. Before the maximum, TMS theory can be used as a good estimate of ?m though it overestimates the actual value. To improve the theory, various corrections to TMS theory were considered: A) Using ion activities instead of ionic concentration in the external solutions leads to an improved prediction; B) Inhomogeneous distribution of the membrane fixed charge has no effect on Φm; C) Consideration of stagnant diffusion layers on each side of the membrane can have a large effect on Φm; D) Reducing the average value of the fixed membrane charge density can also largely affect ?m; E) Allowing for water transport in the theory has a small effect; F) Considering differences in ionic mobility between co-ions and counterions in the membrane affects Φm significantly. Modifications C) and F) may help to explain the observed maximum in Φm.
Gas-permeable hydrophobic membranes enable transport of CO2 and NH3 to improve performance of bioelectrochemical systems
Sleutels, Tom H.J.A. ; Hoogland, Biense ; Kuntke, P. ; Heijne, A. ter; Buisman, C.J.N. ; Hamelers, Hubertus V.M. - \ 2016
Environmental Science : Water Research & Technology 2 (2016). - ISSN 2053-1400 - p. 743 - 748.
Application of bioelectrochemical systems (BESs), for example for the production of hydrogen from organic waste material, is limited by a high internal resistance, especially when ion exchange membranes are used. This leads to a limited current density and thus to large footprint and capital costs. Ion transport between anode and cathode compartment is one of the factors determining the internal resistance. The aim of this study was to reduce the resistance for ion transport in a microbial electrolysis cell (MEC) through the ion exchange membrane by shuttling of CO2 and NH3 between anode and cathode. The transport of these chemical species was enabled through the use of a hydrophobic TransMembraneChemiSorption module (TMCS) that was placed between anolyte and catholyte circulation outside the cell. The driving force for transport was the pH difference between both solutions. The transport of CO2 and NH3 resulted in an increase in current density from 2.1 to 4.1 A m−2 for a cation exchange membrane (CEM) and from 2.5 to 13.0 A m−2 for an anion exchange membrane (AEM) at 1 V applied voltage. The increase in current density was the result of a lower ion transport resistance through the membrane; this resistance was 60% lower for the CEM, as a result of NH3 recycling from cathode to anode, and 82% for the AEM, as a result of CO2 recycling from anode to cathode with TMCS, compared to experiments without TMCS.
Gas-permeable hydrophobic tubular membranes for ammonia recovery in bio-electrochemical systems
Kuntke, P. ; Zamora, P. ; Saakes, M. ; Buisman, C.J.N. ; Hamelers, H.V.M. - \ 2016
Environmental Science : Water Research & Technology 2 (2016)2. - ISSN 2053-1400 - p. 261 - 265.
The application of a gas-permeable hydrophobic tubular membrane in bio-electrochemical systems enables efficient recovery of ammonia (NH3) from their cathode compartments. Due to a hydrogen evolution reaction at the cathode, no chemical addition was required to increase the pH for continuous NH3 recovery from wastewater.