Maarten Biesheuvel

Wetsus · Research Institute

Reverse osmosis (RO) is a method to desalinate water, where water containing salts is pushed through a membrane while salt ions are rejected by the membrane. Very important in the theory of mass transport in RO is the concentration polarization (CP) layer, which develops on the upstream side of the membrane because of a combination of salt convecti...

Bipolar membranes (BPMs), a special class of ion exchange membranes with the unique ability to electrochemically induce either water dissociation or recombination, are of growing interest for environmental applications including eliminating chemical dosage for pH adjustment, resource recovery, valorization of brines, and carbon capture. However, io...

Organic micropollutants (OMPs) in drinking water constitute a potential risk to human health; therefore, effective removal of these pollutants is required. Nanofiltration (NF) and reverse osmosis (RO) are promising membrane-based technologies to remove OMPs. In NF and RO, the rejection of OMPs depends on the properties and characteristics of the me...

Modeling mass transport of ions across the polyamide active layer of a reverse osmosis (RO) membrane requires a comprehensive understanding of membrane structure and chemistry. For instance, membrane charge ionization and thus salt transport greatly depend on feedwater pH and composition, but these relations are not yet well understood. To address...

In nanofiltration (NF), solution and membrane chemistry determine the membrane charge density. In multi-component electrolytes solutions, it is important to consider the interaction between ions and NF membranes. For instance, in the presence of divalent ions, charge reversal can take place due to the interaction of counterions with the charged fun...

Due to the complexity of oil-in-water emulsions, the existing literature is still missing a mathematical tool that can describe membrane fouling in a fully quantitative manner on the basis of relevant fouling mechanisms. Hypothesis In this work, a quantitative model that successfully describes cake layer formation and pore blocking is presented. W...

We analyze selective removal of anions in electrodialysis (ED) from a multicomponent ion mixture where all ions are monovalent, both experimentally and by a modified theory. The theory makes use of the Nernst-Planck equation to describe the transport of ions across ion-exchange membranes in combination with a parameter, the ion affinity, to account...

Polycrystalline alumina substrates were dip-coated in dilute suspensions formed with dispersed, nano-silica particles. The fractional surface coverage of the alumina substrate was varied between ≈ 0.05 to ≈ 0.4 by changing concentration of particles in the silica slurry. After a heat treatment to partially sinter the particles to the surface, the s...

Reverse osmosis (RO) and electrodialysis (ED) are the two most important membrane technologies for water desalination and treatment. Their desalination and transport mechanisms are very different, but on a closer look also have many similarities. In this tutorial review we describe state-of-the-art theory for both processes focusing on simple examp...

Understanding the salt–water separation mechanisms of reverse osmosis (RO) membranes is critical for the further development and optimization of RO technology. The solution-diffusion (SD) model is widely used to describe water and salt transport in RO, but it does not describe the intricate transport mechanisms of water molecules and ions through t...

Reverse osmosis (RO) is the most important membrane technology for the desalination of water. Measured water flow rates and salt fluxes are traditionally analyzed in the context of the solution-diffusion (SD) model which leads to a water permeability, A, and a salt permeability, B. However, the parametrization of the salt flux is not correct for wa...

Electrochemical ion separation (EIONS) is attracting attention as a new ion separation technology because no by-products are generated during the process. However, conventional EIONS systems have lower selectivity for anions; it has limitations in its application to selective anion extraction. Therefore, it is necessary to develop a new EIONS syste...

Reverse osmosis (RO) and electrodialysis (ED) are the two most important membrane technologies for water desalination and treatment. Their desalination and transport mechanisms are very different, but on closer look also have many similarities. In this tutorial review we describe state-of-the-art theory for both processes focusing on simple example...

Significance Water treatment is required for a sustainable potable water supply and can be leveraged to harvest valuable elements. Crucial to these processes is the removal of charge pH-dependent species from polluted water, such as boron, ammonia, and phosphate. These species can be challenging for conventional technologies. Currently, boron remov...

For a thorough mechanistic understanding of reverse osmosis (RO), data on ion retention obtained by desalination of multi-ionic solutions are needed. In this paper, we show how to obtain such data under controlled laboratory conditions at any nonextreme pH. For that, we propose a simple method where we use N2 and CO2 gas control to set the composit...

Several harmful or valuable ionic species present in sea, brackish and wastewaters are amphoteric, and thus their properties depend on the local water pH. Effective removal of these species can be challenging by conventional membrane technologies, necessitating chemical dosing of the feedwater to adjust its pH. Capacitive deionization (CDI) is an e...

Reverse Osmosis (RO) is one of the main membrane technologies currently used for the desalination of seawater and brackish water to produce freshwater. However, the mechanism of transport and separation of ions in RO membranes is not yet fully understood. Besides acid–base reactions (i.e., including the H⁺-ion), at high concentrations, the salt ion...

Microbial electrosynthesis (MES) provides a sustainable route for the conversion of CO2 and electricity into acetate and other organics. The conversion of CO2 takes place at a biologically active cathode (‘biocathode’), which is typically separated from the anode by an ion exchange membrane. Since both charged and uncharged species participate in t...

Though electrodialysis (ED) and reverse osmosis (RO) are both mature, proven technologies for brackish water desalination, RO is currently utilized to desalinate over an order of magnitude more brackish water than ED. This large discrepancy in the adoption of each technology has yet to be thoroughly justified in the literature, particularly from th...

Within the last decade, in addition to water desalination, capacitive deionization (CDI) has been used for resource recovery and selective separation of target ions in multicomponent solutions. In this review, we summarize the mechanisms of selective ion removal utilizing different electrode materials, carbon and non-carbon together with or without...

The activity coefficient of ionic solutions was proposed to depend on the cube root of concentration in the early 20th century by Bjerrum (1916) and Ghosh (1918) because of the good fit with data, for the dilute limit and for moderate concentrations. A theory by Ghosh assumed a lattice-like structure of the distribution of the ions but that is not...

Physics of Electrochemical Processes covers fields as diverse as colloidal interaction, electrowetting, the G/L/S contact angle, electrical double layers, surface pressure, surface ionization, mass transport to interfaces, electrode kinetics, electrokinetics, bio-electrochemical systems, combined reaction and diffusion systems, and water desalinati...

We investigate permeate pH across an RO membrane by modeling transport of ions including protons and hydroxide ions using the extended Donnan steric partitioning pore model (ext-DSP model). We show that membrane charge density plays an important role in determining permeate pH, while the effect of flow rate and salt concentration are less significa...

Binary mixtures of charged nanoparticles become layered upon centrifugation as a result of minimization of the system free energy in sedimentation-diffusion equilibrium. Different factors were investigated experimentally for their effects on the layering, and supported by theoretical calculations of the full sedimentation profiles. Surprisingly, li...

The effect of the thickness of ion exchange membranes has been investigated for electrodialysis (ED) and reverse electrodialysis (RED), both experimentally and through theoretical modeling. By developing a two-dimensional model based on Nernst-Planck theory, we theoretically find that reducing the membrane thickness benefits process performance onl...

During fossil oil extraction, a complex water stream known as produced water (PW), is co-extracted. Membrane treatment makes PW re-use possible, but fouling and oil permeation remain major challenges. In this work, membrane fouling and oil retention of Synthetic PW stabilized with a cationic, anionic, zwitterionic or nonionic surfactant, were studi...

Electrochemical desalination technologies such as capacitive deionization (CDI) and battery desalination (BD) are considered as promising brackish water desalination technologies because of their low energy consumption and environmental friendliness. However, it is a still challenge to develop an efficient way to deionize highly concentrated salt w...

A one-dimensional and stationary reactor model is presented to describe the catalytic conversion of a gaseous hydrocarbon fuel with air and steam to synthesis gas by autothermal reforming (ATR) and catalytic partial oxidation (CPO). The model defines two subsequent sections in the reactor, namely an upstream oxidation section, and a downstream refo...

Electrostatic cooling is known to occur in conductors and in porous electrodes in contact with aqueous electrolytes. Here we present evidence of electrostatic cooling at the junction of two electrolyte phases. These are, first, water containing salt and, second, an ion-exchange membrane, which is a water-filled porous layer containing a large conce...

Electrostatic cooling is known to occur in conductors and in porous electrodes in contact with aqueous electrolytes. Here we present for the first time evidence of electrostatic cooling at the junction of two electrolyte phases. These are, first, water containing salt, and, second, an ion-exchange membrane, which is a water-filled porous layer cont...

In this work, we develop an extended uniform potential (UP) model for a membrane nanopore by including two different charging mechanisms of the pore walls, namely by electronic charge and by chemical charge. These two charging mechanisms will generally occur in polymeric membranes with conducting agents, or membranes made of conducting materials li...

Bioelectrochemical systems are electrochemical cells that rely on conductive biofilms covering an electrode. We consider the example of a microbial fuel cell, and 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...

We present porous electrode theory for capacitive deionization (CDI) with electrodes containing nanoparticles that consist of a redox-active intercalation material. A geometry of a desalination cell is considered which consists of two porous electrodes, two flow channels and an anion-exchange membrane, and we use Nernst-Planck theory to describe io...

Reverse Osmosis (RO) is a membrane-based technology for water desalination. Of paramount importance is the understanding of ion selectivity in mixtures of salts, i.e., to what extent the membrane retains one ion more than another in a multicomponent salt solution. We apply continuum transport theory to describe a large set of data for the ion selec...

In this work, we develop an extended uniform potential (UP) model for a membrane nanopore by including two different charging mechanisms of the pore walls, namely by electronic charge and by chemical charge. These two charging mechanisms generally occur in polymeric membranes with conducting agents, or membranes made of conducting materials like ca...

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 out...

Activated carbon is the most common electrode material used in electrosorption processes such as water desalination with capacitive deionization (CDI). CDI is a cyclic process to remove ions from aqueous solutions by transferring charge from one electrode to another. When multiple salts are present in a solution, the removal of each ionic species c...

Capacitive deionization is a water desalination technology in which ions are stored in electrodes in an electrochemical cell construction, connected to an external circuit, to remove ions present in water from various sources. Conventionally, carbon has been the choice of material for the electrodes due to its low cost, low contact resistance and h...

Capacitive deionization (CDI) typically uses one porous carbon electrode that is cation adsorbing and one that is anion adsorbing. In 2016, Smith and Dmello proposed an innovative CDI cell design based on two cation‐selective electrodes and a single anion‐selective membrane, and thereafter this design was experimentally validated by various authors...

We present a novel theory to predict the contact angle of water on amphoteric surfaces, as a function of pH and ionic strength. To validate our theory, experiments were performed on two commonly used amphoteric materials, alumina (Al2O3) and titania (TiO2). We find good agreement at all pH values, and at different salt concentrations. With increasi...

In the growing field of capacitive deionization (CDI), a number of performance metrics have emerged to describe the desalination process. Unfortunately, the separation conditions under which these metrics are measured are often not specified, resulting in optimal performance at minimal removal. Here we outline a system of performance metrics and re...

In this paper we report the theory describing the electro-osmotic flow in charged nanopores with constant radius and charge density driven by alternating current. We solve the ion and solution transport in unsteady conditions as described by the Navier-Stokes and Nernst-Planck equations considering the electrical potential inside the charged nanopo...

Both Faradaic and non-Faradaic processes can take place at an electrode. The difference between the two processes is clearly discussed in several classical sources, starting with Grahame (1952). However, later reference to charge transfer across the metal-solution interface as a defining feature of a Faradaic process, has led to ambiguities. Follow...

The effect of the thickness of ion exchange membranes has been investigated for electrodialysis (ED) and reverse electrodialysis (RED), both experimentally and through theoretical modeling. By developing a two-dimensional model based on Nernst-Planck theory, we theoretically find that reducing the membrane thickness benefits process performance onl...

We present a porous electrode theory for capacitive deionization with electrodes containing nanoparticles that consist of a redox-active intercalation material. A geometry of a desalination cell is considered which consists of two porous electrodes, two flow channels, and an anion-exchange membrane, and we use the Nernst-Planck theory to describe i...

In the field of Capacitive Deionization (CDI), it has become a common notion that constant current (CC) operation consumes significantly less energy than constant voltage operation (CV). Arguments in support of this claim are that in CC operation the endpoint voltage is reached only at the end of the charging step, and thus the average cell voltage...

In this paper we report the theory describing the electro-osmotic flow in charged nanopores with constant radius and charge density driven by alternating current. We solve the ion and solution transport in unsteady conditions as described by the Navier-Stokes and Nernst-Planck equations considering the electrical potential inside the charged nanopo...

In the growing field of capacitive deionization (CDI), a number of performance metrics have emerged to describe the desalination process. Recent research has shown, however, that the separation conditions under which these metrics are measured must be specified, otherwise optimal performance occurs at minimal removal. Here we outline a system of pe...

Capacitive deionization is a desalination technology to remove ions from aqueous solution in a cyclic manner by applying a voltage between pairs of porous electrodes. We describe the dynamics of this process by including a possible rate limitation in the transport of ions from the interparticle pore space in the electrode into intraparticle pores,...

Capacitive deionization (CDI) for water treatment, which relies on the capture of charged species to sustain the electrical double layers (EDLs) established within porous electrodes under an applied electrical potential, can be enhanced by the chemical attachment of fixed charged groups to the porous electrode electrodes (ECDI). It has recently bee...

Mechanical-energy harvesters based on coiled carbon nanotube yarns are promising materials for sustainable energy generation. In this work, we present a novel mechanism to harvest energy from mechanical fluctuations by using coiled carbon nanotube yarns coated with polyelectrolyte gel. We developed a theory to explain how this new kind of energy ha...

It is a widely accepted principle that a thermodynamically reversible desalination process should consume the Gibbs free energy of separation. This principle has been shown in reverse osmosis and has important practical implications in reducing its energy consumption. Capacitive deionization (CDI) with carbon electrodes, a desalination process base...

Over the past decade, capacitive deionization (CDI) has realized a surge in attention in the field of water desalination and can now be considered as an important technology class, along with reverse osmosis and electrodialysis. While many of the recently developed technologies no longer use a mechanism that follows the strict definition of the ter...

Coulometric measurements on salt-water-immersed nanoporous carbon electrodes reveal, at a fixed voltage, a charge decrease with increasing temperature. During far-out-of-equilibrium charging of these electrodes, calorimetry indicates the production of both irreversible Joule heat and reversible heat, the latter being associated with the ionic entro...

We present theory for ion and water transport through reverse osmosis membranes based on a Maxwell-Stefan framework combined with hydrodynamic theory for the reduced motion of particles in thin pores. We include all driving forces and frictions both on the fluid (water), and on the ions, including ion-fluid friction as well as ion-wall friction. By...

In electrochemical water desalination, a large difference in pH can develop between feed and effluent water. These pH changes can affect the long-term stability of membranes and electrodes. Often Faradaic reactions are implicated to explain these pH changes. However, quantitative theory has not been developed yet to underpin these considerations. W...

The Donnan model describes the electric double layer structure inside carbon micropores and is an essential element of larger-scale models for capacitive and Faradaic porous carbon electrodes for energy storage and water desalination. The Donnan model was not yet developed to describe the expansion of carbon electrodes upon charging. Here we provid...

Capacitive deionization (CDI) is a fast-emerging water desalination technology in which a small cell voltage of ~1 V across porous carbon electrodes removes salt from feedwaters via electrosorption. In flow-through electrode (FTE) CDI cell architecture, feedwater is pumped through macropores or laser perforated channels in porous electrodes, enabli...

Using porous electrodes containing redox-active nickel hexacyanoferrate (NiHCF) nanoparticles, we construct and test a device for capacitive deionization in a two flow-channel device where the intercalation electrodes are in direct contact with an anion-exchange membrane. Upon reduction of NiHCF, cations intercalate into it and the water in its vic...

We demonstrate the phenomenon of induced-charge capacitive deionization that occurs around a porous and conducting particle immersed in an electrolyte, under the action of an external electric field. The external electric field induces an electric dipole in the porous particle, leading to its capacitive charging by both cations and anions at opposi...

Transport of water through ion-exchange membranes is of importance both for electrodialysis (ED) and reverse electrodialysis (RED). In this work, we extend our previous theory [J. Membrane Sci., 510, (2016) 370-381] and include water transport in a two-dimensional model for (R)ED. Following a Maxwell-Stefan (MS) approach, ions in the membrane have...

We use space-charge (SC) theory (also called the capillary pore model) to describe the ionic conductance, $G$, of charged carbon nanotubes (CNTs). Based on the reversible adsorption of hydroxyl ions to CNT pore walls, we use a Langmuir isotherm for surface ionization and make calculations as function of pore size, salt concentration $c$, and pH. Us...

While the world faces an increased scarcity in fresh water supply, it is of great importance that water from industry and waste streams can be treated for re-use. One of the largest waste streams in the oil and gas industry is produced water. After the phase separation of oil and gas, the produced water is left. This mixture contains dissolved and...

We demonstrate the phenomenon of induced-charge capacitive deionization (ICCDI) that occurs around a porous and conducting particle immersed in an electrolyte, under the action of an external electrostatic field. The external electric field induces an electric dipole in the porous particle, leading to capacitive charging of its volume by both catio...

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) the...

We revisit Morrison and Osterle (1965) who derived a phenomenological expression for the 'figure-of-merit' B_EK of the electrokinetic energy conversion (EKEC) of a pressure difference into electric energy (and vice versa) using charged nanotubes, nanopores or ion-exchange membranes. We show the equivalence with Morrison and Osterle of a novel expre...

We revisit the classical problem of flow of electrolyte solutions through charged capillary nanopores or nanotubes as described by the capillary pore model (also called “space charge” theory). This theory assumes very long and thin pores and uses a one-dimensional flux-force formalism which relates fluxes (electrical current, salt flux, and fluid v...