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Student assignments

Information on student assignments with MST

Looking for an assignment? Please contact us for the possibilities at the Membrane Science & Technology cluster. Below are our vacant  student assignments. 


Preparation and characterization of new pH stable nanofiltration membranes prepared by interfacial polymerization (MSc or BSc assignment)

Project Scope

Nanofiltration membranes are used in a wide variety of industries. Advantages such as low energy cost, ease of application, operation at moderate conditions and no extra waste streams, makes that membrane technology can offer both economic and ecologic benefits. However, the insufficient stability of the membranes currently limits their application in extreme industrial conditions such as at extreme pH values, in e.g. the mining, textile or dairy industry. 

For extreme pH conditions (i.e. below 2 and above 12.5), only a few membranes are available, and often they have inadequate stability, low flux/rejection making them unsuitable for large-scale implementation.

In this project, we try to develop new polymeric nanofiltration membranes, which tackle the currently existing shortcoming of commercial membranes.

The technique used for preparing the membranes is interfacial polymerization. A thin selective toplayer is formed on a porous support (figure 1) by reacting two monomers at the interface of two immiscible phases (figure 2).

Your task:

During this research you will focus on the development and characterization of nanofiltration membranes. You will focus on the exploration of new chemistries, leading to pH stable membranes (inspired by the work of Kah Peng Lee 3,4). You will test the potential of several monomer combinations for its film formation and its use as selective layer on pH stable membranes. The prepared films and membranes will be characterized by means of a.o. FTIR, SEM, zeta potential, clean water flux, salt retention, MWCO and stability tests in extreme pH.

Contact:

If you are interested to work on this topic or if you want more information, please contact Mariël Elshof (m.g.elshof@utwente.nl), Films in Fluids, ME236B.

Reference:

  1. Dalwani, M. Thin film composite nanofiltration membranes for extreme conditions. Ph.D.Thesis (2011).
  2. Raaijmakers, M. J. T. & Benes, N. E. Current trends in interfacial polymerization chemistry. Prog. Polym. Sci. 63, 86–142 (2016).
  3. Lee, K. P., Zheng, J., Bargeman, G., Kemperman, A. J. B. & Benes, N. E. pH stable thin film composite polyamine nanofiltration membranes by interfacial polymerisation. J. Memb. Sci. 478, 75–84 (2015).
  4. Lee, K. P., Bargeman, G., de Rooij, R., Kemperman, A. J. B. & Benes, N. E. Interfacial polymerization of cyanuric chloride and monomeric amines: pH resistant thin film composite polyamine nanofiltration membranes. J. Memb. Sci. 523, 487–496 (2017).
Ion transport through graphene (MSc assignment)

Graphene is increasingly studied as a potential material for membrane applications. It does not have any separation capability in its pristine state, however a perforated monolayer graphene membrane can selectively separate material due to steric or electrostatic exclusion [1, 2].  In our work, we use ion-bombarded perforated monolayer graphene membrane supported on a polymer foil to study diffusional ion transport properties through graphene [3]. This membrane allows positive ions to pass through and blocks negative ions, acting as a cation-exchange membrane (CEM). We have studied the selectivity of the membrane with varying concentrations from range where Donnan potential dominates to concentrations where the diffusion potential dominates and the membrane loses all its selectivity. We have also analyzed our experimental results with theory, based on Donnan equilibrium and the Teorell, Mayer and Sievers (TMS) theory.  

 

So far, we have done our measurements without applying any electric field across the membrane and the observations are based on diffusional ion transport. Now, we need to explore how the ions transport through the membrane when an electric field is applied across the membrane. The aim of the current master’s project is to study the ion transport behaviour of the graphene membrane with the application of electric field. Also, in the later part of the project the ion transport will be studied with varying number of pores in the membrane. Finally, the experimental result will be validated with theoretical understanding.  

For more information, feel free to contact Madakranta (Dona) Ghosh:
m.ghosh@utwente.nl

[1] O’Hern et al. “Selective Ionic Transport through Tunable Subnanometer Pores in Single-Layer Graphene Membranes.” Nano Lett. 2014, 1234-1241

[2] Rollings et al. “Ion selectivity of graphene nanopores” Nature Comm., 2016, 7, 11408

[3] Madauß et al. “Fabrication of nanoporous graphene/polymer composite membranes” Nanoscale, 2017, 9, 10487

Theoretical Investigation of Electroforming MOFs on Copper Hollow Fibers (MSc assignment)

Recently in the Films in Fluids group a novel technique for producing highly controllable hollow fibres using an environmentally friendly ionic-gelation technique has been developed. Through the addition of nanoparticles, metallic oxide or metallic hollow fibres can be easily fabricated. Using this technique, the FiF group has pursued the intriguing idea of utilizing this simple fibre production technique in order to fabricate copper-based metal organic frameworks (MOFs). MOFs are metal-ions which are coordinated to organic ligands, forming network structures (1d, 2d or 3d) that can be porous. MOFs are of potential interest in catalysis, sensing and gas separation and having the capacity to form high specific surface area hollow fibres is an attractive option for making use of the unique MOF properties.

Research has been carried out in fabricating Cu(BTC) using an electrochemical synthesis method. In this approach, a Cu hollow-fibre is used as the working electrode in a cell containing an ethanol-water mixture containing an organic ligand - trimesic acid (BTC). BTC then reacts with copper to form Cu-BTC, a copper-hollow fibre MOF. The underlying mechanism behind this transformation and its enhancement using applied potential has been postulated but not confirmed.

It is the goal of this proposed Masters assignment to develop a theoretical model to understand this system, which we are presently investigating experimentally. This model framework can then be implemented in a 2 or 3d numerical simulation (COMSOL) in order to predict or fit experimental results. For example, what is the role of the electric-field distribution within the system, ion dissociation in the water-ethanol mixture, etc. This will greatly aid in understanding of the potential of this approach for synthesis of MOF hollow-fibres and its potential applicability at larger scales.

For more information, please contact:

Özlem Haval Demirel (o.h.demirel@utwente.nl), Films in Fluids, Meander 322

Jeff Wood (j.a.wood@utwente.nl), Soft Matter, Fluidics and Interfaces, Meander 313

[1] Schäfer et al. Unraveling a two-step oxidation mechanism in electrochemical Cu-MOF synthesis. Chem. Comm. 2016. 52: 4722

Catalytically Induced Convective Flow

The electrochemical decomposition of hydrogen peroxide  has been reported to generate interfacial fluid flow by micro-pumps, and interdigitated microelectrodes[1], as well as the motion of bimetallic platinum/gold nano-motors [2]. In principle, the immersion of platinum/gold nanorods in hydrogen peroxide, triggers a series of oxidation and reduction reactions, where  is oxidized at the platinum anode into protons, electrons, and oxygen molecules, while reduction takes place at the gold cathode. The resulting ionic flux generates an electric field that is coupled with the charge density, thereby inducing an electric body force that drives interfacial fluid motion.The heterogeneous rate constant which largely influences ionic flux by way of proton generation and consumption is an important parameter that needs to be understood under steady state and transient conditions.

The kochi and Kolinger’s approach [3] will be used in determining the reaction rate constant. Several electrochemical experimental techniques such as chronoamperometry, chronopotentiometry and cyclic voltammetry, will be used in determining important parameters such as, diffusion coefficient, charge transfer, number of electrons, and peak potentials needed for evaluating the rate constant. The experimental heterogenous rate constant will be implemented in existing numerical models by way of the Damköhler’s number to ascertain its influence on the reaction flux, proton distribution, induced potential and convective flow.

For more information, contact:

Abimbola ASHAJU (a.a.ashaju@utwente.nl), Soft Matter, Fluidics and Interfaces, Meander 317)

[1]          T. R. Kline, W. F. Paxton, Y. Wang, D. Velegol, T. E. Mallouk, and A. Sen, “Catalytic micropumps: Microscopic convective fluid flow and pattern formation,” J. Am. Chem. Soc., vol. 127, no. 49, pp. 17150–17151, 2005.

[2]          T. R. Kline, W. F. Paxton, T. E. Mallouk, and A. Sen, “Catalytic Nanomotors: Remote-Controlled Autonomous Movement of Striped Metallic Nanorods**,” pp. 744–746, 2005.

[3]          R. J. Klingler and J. K. Kochi, “Electron-transfer kinetics from cyclic voltammetry. Quantitative description of electrochemical reversibility,” J. Phys. Chem., vol. 85, no. 12, pp. 1731–1741, 1981.

Multicomponent nanofiltration modeling

Nanofiltration membranes are commonly employed in industrial practice for separations of molecular species while working at relative low operation pressures. The unique property of these membranes is that they allow passage of certain solutes, while they can retain others. This makes nanofiltration a cost-effective step in the separation or purification of several streams. This can for instance be drinking water production, or resource recovery from waste streams. For an effective process, it is essential to understand the transport of the different solutes to and through the membrane. 

One observed non-ideality is the emergence of non-intuitive phenomena, such as negative retention of solutes (the permeate of a process is more concentrated than the retentate). This is, in particular, more common in mixture systems due to the fascinating non-ideal thermodynamics involved and has important consequences in the design and operation of membrane processes for separations. Building a model framework that can capture these effects and understand the role of mixture interactions in a simple manner is therefore of crucial importance.

In this assignment, you will work to build and compare multicomponent mass transfer models and compare the role of choosing an effective mixture thermo-dynamics rule + model framework in describing experimental data for hollow fiber filtration. The aim is to be able to describe industrially relevant hollow fiber filtration data obtained from actual membrane filtration experiments. The assignment will be performed at the UT in close collaboration with an industrial partner (NX Filtration).

For more information please contact Jeff Wood (j.a.wood@utwente.nl) or Joris de Grooth (j.degrooth@utwente.nl)

Future generation membranes by Aqueous Phase Separation

Elif Nur Durmaz (1), Wouter Nielen(1), Joshua Willott  (1), Wiebe de Vos(1)

(1)Membrane Surface Science (MSuS), Membrane Science and Technology Cluster

Project Outline

Membranes are used in a variety of processes including the production of clean drinking water, artificial kidneys, COcapture, and food processing. Due to their large application areas and many advantages of membranes over other separation technologies, the membrane market is continuously growing. However, a major concern regarding membrane production is the use of large quantities of aprotic organic solvents such as N-Methyl-2-pyrrolidone. Such solvents are harmful to humans and the environment. This project is focused on investigating a novel, environmentally friendly technique for the production of membranes without using organic solvents. Here, membrane formation relies on the phase separation of polyelectrolytes either through a pH switch or a complexation with an oppositely charged polyelectrolyte. The main aim is to understand which factors govern the morphology and separation performance of the membranes. Additionally, improving mechanical and chemical stability with cross-linking will be investigated.

     

Figure 1. A schematic representation aqueous phase separation using a weak polyacid.

Project Description

Polyelectrolytes are polymers that contain repeating charged groups. Due to these charges, they are soluble in polar solvents like water. Polyelectrolytes can be separated into two categories based on the charged groups. Weak: when their charge depends on the pH of the medium or strong: when the charge is independent of pH. Weak polyelectrolytes can be used to precipitate a hydrophobic polyelectrolyte from water by shifting to a pH where the polyelectrolyte is uncharged.  Alternatively, when two oppositely charged polyelectrolytes are mixed, they form a complex, which can be solid. In both cases, a phase separation occurs and under the right conditions, this can be used to form a porous, asymmetric membrane. By controlling the rate at which the polyelectrolyte is charged or uncharged the kinetics of the phase separation can be controlled which in turn gives control over the structure of the precipitate that is formed. This allows us to fabricate membranes with controllable properties. To fine-tune membrane performance (e.g. membrane flux or retention), additives can be used. Additionally, the mechanical and chemical stability can be significantly improved with cross-linking. To assess the membrane performance several filtration techniques are used. In addition, the morphology is imaged using scanning electron microscopy. The membrane can then be optimized towards specific applications, such as gas-separation, ion removal or the treatment of oily wastewater.

Project Outcome

This project is expected to lead to a new and sustainable approach to produce membranes. Moreover, the newly produced membranes are expected to have unique separation properties relevant to a number of applications.

Membranes by Aqueous Phase Separation (APS): Effect of polyelectrolyte molecular weights on the membrane properties

Muhammad Irshad Baig(1), Wiebe M. de Vos(1)

(1)Membrane Surface Science,  Membrane Science and Technology Cluster, MESA+ Institute for Nanotechnology, University of Twente, Faculty of Science and Technology, P.O. Box 217, 7500 AE, Enschede, The Netherlands.

m.i.baig@utwente.nl ; w.m.devos@utwente.nl

Project Background

A membrane is  a barrier that regulates the flow of species in a selective way. The most commonly used membranes in water purification and gas separation applications are made from polymers that are only soluble in organic solvents. Ask anyone who works in the field of polymeric membranes about its fabrication procedure, and you will mostly hear one answer i.e. NIPS. It stands for Non-solvent Induced Phase Separation. Simply put, you take a polymer (Polysulfone, Polyimides for example) and dissolve it in an organic solvent such as N-methyl-2-pyrrolidone (NMP). When the solution is homogeneously mixed, it is then cast on a flat surface and put in a water bath. The solvent (NMP) is highly miscible in water and so it diffuses out of the polymer solution and mixes with water. The polymer, at this point becomes insoluble due to all the water that is around it, forming a solid porous membrane. The membranes prepared in this way are also known as ‘Loeb-Sourirajan Membranes (L-S membranes)’, named after the researchers who first made asymmetric cellulose acetate membranes for sea water desalination.

Figure 1. Schematic illustration of the polyelectrolyte complex membrane formation. 

This simple procedure of making commercial polymer membranes has remained the same since the 1970’s. NMP is by far the most widely used solvent to prepare membranes and the multi-billion dollars membrane industry uses this solvent in immense amounts.

However, NMP is not a friendly chemical by any means. It is partly flammable, and most importantly, it has been proven to be repro-toxic to humans and harmful for the environment.1 Therefore, it has to be recycled and/or removed from waste streams plus it has to be removed from the membranes before they can be utilized for water production. The EU has introduced a law that restricts the use of such chemicals throughout the Union.2 

Having discussed the nature of aprotic, polar organic solvents and their harmful effects, we have an alternative solution which uses only water as a solvent. It is extremely difficult and mostly impossible to dissolve conventional polymers in water. This leaves us with a special class of polymers called ‘Polyelectrolytes’ which can be easily dissolved in water. These polyelectrolytes are charged polymers with a unique property that their charge can be manipulated by a pH switch. Some polyelectrolytes are only charged below a particular pH. They are called weak polyelectrolytes. On the other hand, certain polyelectrolytes remain charged in almost all the pH range. These are called strong polyelectrolytes. When the two oppositely charged polyelectrolytes come across each other, they instantly form a ‘Polyelectrolyte Complex’. So if we make a homogeneous solution of these two polyelectrolytes such that they are uncharged in the solution and then cast it in a water bath with a pH where both become charged, we get a polyelectrolyte complex membrane (Figure 1). This novel approach to making membranes is termed ‘Aqueous Phase Separation’ (APS). 

Project Details and Outcome

In this project, Poly(sodium 4-styrenesulfonate) and Polyethyleneimine will be used the polyelectrolytes, respectively. The aim of this project is to  develop free-standing membranes using the two polyelectrolytes mentioned above. During the course of the project, Monomer mixing ratio, effect of coagulation bath pH, cross-linking conditions, and type of salt in coagulation bath would be investigated in detail.

The membranes prepared in this study will be used for water treatment and purification applications. The applications are as diverse as the new APS field itself. From oil/water separation (Microfiltration) to sea water desalination (nanofiltration and reverse osmosis), the outcomes of this study are diverse.  It is noteworthy that one of the inventors of L-S membranes, Loeb Sidney, was a MSc. student at UCLA when he got the breakthrough in membrane science and technology. Similarly, this project, part of a larger research goal, will play an important role in shaping the next generation of polyelectrolyte membranes.

References

  1. D. Prat, J. Hayler and A. Wells, Green Chem., 2014, 16, 4546–4551.
  2. The European Commission, Off. J. Eur. Union, 2018, 99, 3
Polyelectrolytes for an improved aquaporin embedded top layer for next generation forward osmosis membranes (MSc assignment)

Dennis Reurink(1), Wiebe M. de Vos (1)

(1)Membrane Surface Science (MSuS)

Introduction

An emerging separation and desalination technology that shows great potential is forward osmosis (FO). FO uses osmotic pressure gradients to transport water across a semipermeable membrane. These membranes are usually based on reverse osmosis (RO) membranes, which lack, however, suitability for FO applications [1]. A way to create new membranes truly optimized for FO, is by incorporating aquaporin containing vesicles (AQPVs) in the separating layer [2]. These vesicles have the aquaporin protein incorporating in the vesicle wall as shown in Figure 1. This aquaporin protein acts as a water channel that allows solely water and block all other solutes [3]. In this way the permeation and rejection properties are enhanced.

Another versatile technique is the self-assembly of oppositely charged polyelectrolytes (PEs) on the surface of a porous support membrane. In this so-called Layer-by-Layer (LbL) assembly, the support membrane is alternatively exposed to polycations and polyanions [4]. Such a PEM coating is easily applied on all geometries. In this study, the focus will be on making a PEM coating with the incorporation of AQPVs. Since the interaction between the vesicles and the multilayer is important, the distribution of the AQPVs is first studied. Subsequently, a layer will be produced and tested on its FO and RO performance.

Study

In order to create a more permeable and selective layer, aquaporin containing vesicles (AQPVs) can be used. These vesicles are incorporated in the separating layer of the membrane.

In order to control the distribution of the aquaporin vesicle, various polyelectrolytes can be used which have different interaction with the AQPVs. Also different coating environments, like salt concentration, pH, and solvent can be used to control the distribution of the vesicles.

In this MSc project, the distribution of the AQPVs will be studied on model surfaces. When the distribution is controlled and understood a separating layer will be made and incorporated on a membrane.

Methods

PEMs can be made by dip-coating silicon wafers or membranes in a solution containing a certain polyelectrolyte. AQPVs can be also be coated by means of dip-coating.

The distribution of AQPVs can be seen with a high resolution scanning electron microscope. Adsorption of both the PEs and AQPVs are measured with reflectometry and further characterization can be done with ellipsometry, zeta potential, and contact angle measurements. The knowledge obtained from model surfaces (silicon wafers) will be translated into hollow fiber membranes. The membranes will be coated under the same conditions as the model surfaces and will be tested on their performances in forward and reverse osmosis operating conditions.

Figure 1: The water-selective aquaporin protein incorporated in the vesicle wall.

References

1. Shaffer, D.L., et al., Forward osmosis: Where are we now?, Desalination, 2015. 356.

2. Tang, C., et al., Biomimetic aquaporin membranes coming of age, Desalination, 2015. 368.

3. Murata, K., et al., Structural determinants of water permeation through aquaporin-1, Nature, 2000. 407(6804).

4. Decher, G., Fuzzy Nanoassemblies: Toward Layered Polymeric Multicomposites, Science, 1997. 277(5330).

Polyelectrolytes for new generation reverse osmosis hollow fiber membranes (MSc assignment)

Dennis Reurink (1), Wiebe M. de Vos (1)

(1)Membrane Surface Science (MSuS)

Introduction

Nowadays most membranes for nanofiltration (NF) and reverse osmosis (RO) are based on thin film composite (TFC) membranes. On a TFC membrane, a thin film is coated on a porous support with interfacial polymerization. A major disadvantage is that defect free hollow fiber membranes based on the TFC principle is merely impossible [1]. A new versatile technique for membrane the self-assembly of oppositely charged polyelectrolytes (PEs) on the surface of a porous ultrafiltration support membrane. In this so-called Layer-by-Layer (LbL) assembly, the support membrane is alternatively exposed to polycations and polyanions [2]. Such a polyelectrolyte multilayer (PEM) coating is easily applied on all geometries. In this study, the focus will be to create a PEM based membrane suitable for RO applications. In order to achieve RO performance, PEMs should be made as dense as possible by means of crosslinking and the use of different kinds of PEs. Subsequently, the layer will be characterized and tested on its RO performance.

Study

Creating more intrinsic bonds will increase the rejection properties of an active membrane layer. Crosslinking is a manner to create more intrinsic bonds and can easily be done by heat or a catalyst. Many moieties of PEs are amines or carboxylic acids which can easily be crosslinked, as shown in Figure 1.

Crosslinking of PEMs has already shown to be a promising way to create an active layer capable of retaining salts [3]. For FO purposes, the layer has to be as dense as possible in order to cope with highly concentrated saline streams. In order to control the layer density, different materials can be used that influence the intermolecular distance.

In this MSc project, different types of crosslinking techniques and materials will be evaluated. Materials will vary from aliphatic, branched, to aromatic structures while controlling and monitoring the performance of the membrane. 

Methods

PEMs can be made by dip-coating silicon wafers or membranes in a solution containing a certain polyelectrolyte. The growth and properties of these multilayers can be monitored by using techniques like reflectometry, ellipsometry, contact angle, and zeta potential measurements. 

Crosslinking can be done catalyzed or non-catalyzed. Non-catalyzed reactions take place under the influence of heat. To see if crosslinking has taken place, the layer will be characterized by, e.g., FTIR measurements.

The knowledge obtained from model surfaces (silicon wafers) will be translated into hollow fiber membranes. The membranes will be coated and crosslinked under the same conditions as the model surfaces and will be tested on their performances in forward osmosis operating conditions.

Figure 1: Crosslinking of polyelectrolyte multilayers [4].

References

1. Lau, W.J., et al., A recent progress in thin film composite membrane: A review, Desalination, 2012. 287.

2. Decher, G., Fuzzy Nanoassemblies: Toward Layered Polymeric Multicomposites, Science, 1997. 277(5330).

3.  Park, J., et al., Desalination membranes from pH-controlled and thermally-crosslinked layer-by-layer assembled multilayers, Journal of Materials Chemistry, 2010. 20(11).

4.  Sullivan, D.M. and M.L. Bruening, Ultrathin, cross-linked polyimide pervaporation membranes prepared from polyelectrolyte multilayers, Journal of Membrane Science, 2005. 248(1-2).

Studying the nanoscale properties of polymer brush coatings with different architectures

Joshua Willott (1), Wiebe M. de Vos (1)

 (1) Membrane Surface Science (MSuS)

Project Outline

Solid surfaces coated with water-soluble stimuli-responsive polymers (specifically end-tethered brushes) exhibit many diverse macroscopic behaviors such as tuneable wettability and lubrication. For these promising coatings to be applied in ‘real world’ scenarios their nanoscale properties (solvation, charge state, thickness) and how they response to stimuli (pH, temperature, salt) and stresses (confinement, added foulants like surfactants, particles) must be very well understood.

The scope of this project encompasses designing specific polymer architectures to control the responsive nature of end-tethered polymer layers. Recently, it has been shown that polydispersity within such layers can be used to control its thickness response. However, this is difficult to achieve synthetically, and something that can be easier to control is polymer architecture. The polymeric layers will be designed and then studied using numerical self-consistent field theory (Willott et al. 2018, Macromolecules 51, 1198-1206 and Langmuir, 2019, 35, 2709-2718) with comparisons made to experimental observations.

 

Project Description

In this project, you will work to investigate how the architecture (molecular structure) of end-tethered polymer chains (e.g. linear, star, comb, dendrimer) changes their solution behaviour. The polymer response to stimuli including temperature, pH, salt concentration and salt type will also be studied by changing the type of monomers (or segments) and the solvent. Preliminary work shows that architecture is a control parameter for brush behaviour as shown in Figure 1 where linear and comb polymers are compared. Figure 1 also shows that behaviour depends on which sections within the brush contain the responsive monomers.

Figure 1. Thickness response of the polymer layer as a function of chi parameter (proportional to temperature) for linear vs. comb polymer architectures.

Thin film composite (TFC) membranes for organic solvent nanofiltration (BSc or MSc assignment)

 1.     Project description 

The invention of thin film composite (TFC) membranes has revolutionized the desalination industry. It not only lowers the price of fresh water, but also improves the quality of clean water. A typical TFC membrane consists of two different layers, a selective layer on top and a porous substrate underneath. The selective layer is commonly made from conventional interfacial polymerization, coating or layer-by-layer method while the substrate is a ultrafiltration membrane. The main advantage of TFC membranes is that one can manipulate both layers separately in such a way to produce a highly permeable and selective membrane.

Despite all the advantage of membrane based separations, their application in petrochemical and pharmaceutical industries are still limited because most separations in these industries involve organic solvents or extreme pH, where conventional polymer membranes fail to operate. Therefore, design and fabrication of chemically stable TFC membranes with great mechanical and thermal stabilities are highly demanded for sustainable manufacturing in chemical and pharmaceutical industries.

In this project we are looking into developing novel and highly stable selective layers, while a commercially available substrate would be used for the substrate. The newly developed membranes would be tested under harsh/real industrial conditions. This include organic solvents and acidic solutions.

2.    Your tasks 

  • TFC membrane synthesis
  • Operation of dead-end filtration systems. 
  • Membrane characterizations such as FESEM, FTIR, etc.

 3.    Your profile 

  • Specialized in environmental/chemical engineering, chemistry or related areas.
  • Actively enrolled in undergraduate (BSc) or graduate (MSc) studies 
  • An interest for practical laboratory experience.
  • Fluent in English language (speaking, writing and communication skills) 

Duration of the project: 6-9 months

4.     How to apply 

Interested students are invited to contact Akbar Asadi Tashvigh (a.asaditashvigh@utwente.nl) for more details.

 

[1]. Asadi Tashvigh, A., et al., 110th Anniversary: Selection of Cross-Linkers and Cross-Linking Procedures for the Fabrication of Solvent-Resistant Nanofiltration Membranes: A Review. Industrial & Engineering Chemistry Research, 2019. 58(25): p. 10678-10691.

[2]. Asadi Tashvigh, A. and T. S. Chung, Facile fabrication of solvent resistant thin film composite membranes by interfacial crosslinking reaction between polyethylenimine and dibromo-p-xylene on polybenzimidazole substrates. Journal of Membrane Science, 2018. 560: p. 115-124.

Development of supported thin film membranes for hydrogen separation (MSc assignment)

Announcing Institution: Forschungszentrum Jülich GmbH, IEK-1 – Materials Synthesis and Processing and University of Twente – Electrochemistry Research Group

Starting date: anytime, Duration: 7 Months

Field of activity: The energy supply in Europe has changed in the past few decades from conventional technologies (fossil, nuclear) to more renewables (solar, wind) and the process is still going on. This leads to a high fluctuation of the energy supply and to times of over- and undercapacity. To ensure a sustainable and environmental friendly energy supply for the future, carbon capture technologies are necessary to reduce CO2 emissions, and energy storage is needed to cover periods of low energy generation by renewables. The development of new batteries or the production of synthetic fuels is urgently required for energy storage.

Oxide ceramic membranes for the separation of oxygen or hydrogen from gas mixtures are of great interest for different applications due to their high efficiency and practically infinite selectivity. Supported membrane structures are envisaged for applications in oxygen and hydrogen generation for the corresponding gas supply, for example in power plants, glass, cement or steel production, as well as for chemical or petrochemical applications and for green energy generation (H2). In addition, ion-conducting ceramic membrane reactors make it possible to combine membrane separation processes directly with chemical reactions, leading to process intensification and, hence, benefits with regard to efficiency. Current research activities focus on membrane reactors due to their high intrinsic efficiency and great potential for the production of a large variety of commodity chemicals, energy carriers, and synthetic fuels.

Description of work: The proposed master thesis targets the development of BaZr0.8Y0.15Mn0.05O3-δ gastight membranes with several micrometers thickness on a porous support. In addition the microstructure must be optimized and fully characterized regarding performance and sintering behavior. Aim is to increase the hydrogen permeation of the membrane by modifying structure and surface area. The manufacturing of the membranes will be done by sequential tape casting or another reasonable method. Tailoring of the microstructure of the support will be done by modifying the amount of pore former in support and the adjustment of sintering behavior. Sufficient porosity and tortuosity are needed to avoid polarization effects. An enhanced surface area on both sides of the membrane increases the hydration effect. Before starting the experimental work a literature study has to be done to check the state of the art. A detailed work plan will be provided after first discussion with the candidate.

Requirements
Knowledge in materials science ideally ceramics; ability of hands-on lab work; good English skills

Contact person – Forschungszentrum Jülich
Prof. Dr. Wilhelm A. Meulenberg
Phone: +49 2461 61-6323 
E-Mail: w.a.meulenberg@fz-juelich.de

Contact person – University of Twente
Prof. Dr. Henny Bouwmeester
E-Mail: h.j.m.bouwmeester@utwente.nl
Tel:+31 53 489 2202

The main work will be carried out at Forschungszentrum Jülich in Germany. Forschungszentrum Jülich GmbH will cover some living costs for the stay in Jülich.

Sieving of hot gases by thin film composite membranes (MSc assignment)

Project outline:

Global warming due to greenhouse gas emissions is one of the worldwide concerns. Among these gases, CO2 has been recognized as the most responsible one. Many efforts have been made to fabricate membranes, which can separate H2 from CO2 in harsh conditions. Recently, IPOSS membranes show breakthrough results for H2/CO2  selectivities at temperatures up to 300°C, which makes them ideal for using them in the pre-combustion capture.

IPOSS membranes are polyimide membranes which contain POSS (Polyhedral oligomeric silsesquioxane) as the main building block. They are produced by using a two-step procedure: the interfacial polymerization of POSS and anhydride on a ceramic layer (Fig 1.a), followed by thermal imidization (Fig 1.b). The thickness of the produced layer is less than 100 nm [1].

Figure 1. two-step procedure of producing IPOSS membranes [1]

Project description:

This master thesis aims to enhance the performance of IPOSS membranes. To achieve this, Palladium (Pd) nanoparticles can be used. These nanoparticles are only selective toward H2 and using them in the iPOSS membrane will improve the H2 permeability and H2/CO2 selectivity.

There are different ways to add Pd nanoparticles to the membranes. In this assignment, you will explore these methods and investigate its effect on the performance of the membranes.

Project outcome:

This project is a new approach for producing thin film composite (TFC) membranes contain nanomaterials.

Contact:

For more information, feel free to contact Farzaneh Radmanesh (f.radmanesh@utwente .nl)

References:

1.           Raaijmakers, M.J., and N.E. Benes, Current trends in interfacial polymerization chemistry. Progress in polymer science, 2016. 63: p. 86-142.

Influence of thermal history on the oxygen surface exchange for SOFC cathode materials (MSc assignment)

Background

Perovskite oxides belonging to the family; (La1-xSrx)s(Co1-yFey)O3-δ (1 ≥ x ≥ 0, 1 ≥ y ≥ 0, s = 1) have found use as electrodes for solid oxide cells (SOC) and oxygen sensors and are also being explored as potential materials for oxygen separation membranes. This is due to their good ionic and electronic transport properties, high activity for oxygen reduction/ evolution reactions (ORR/OER) and the fact that via tailoring the composition, properties can be ‘tuned’ with a view to the specific application. When assessing the performance of a particular perovskite composition, one usually compares the catalytic activity with a reference, a non-modified sample or a literature value. However, establishing a suitable reference point is not necessarily trivial. A good illustration is given by Bobing et al.1 where a literature review reveals that the results of surface exchange coefficient (kchem) differ over one order of magnitude even for the same cathode material (fig. 1). One of the factors responsible for this scatter in literature is that the thermal history of the samples prior to measurement is rarely detailed. Furthermore, it is often not clear how stable the reported enhancements are and whether the reference samples have representative and stable performance themselves.

Fig.1 Hu, B., & Xia, C. Asia-Pacific J. Chem. Eng. (2016)


Project description

In this project, the aim is to investigate the dependence of oxygen surface exchange rate on the thermal history of LAF64. The candidate will benefit of the expertise and equipment of Electrochemistry Research Group (ECRG) to:

  1. Synthesize LAF64 powder and dense pellets from the protocol described in literature and developed in ECRG previously.
  2. Characterize the as-prepared membranes by various techniques like LEIS, XRD, electron microscopy, XPS, etc...
  3. Finding key parameters (e.g. variations in composition, effect of microstructure and surface composition) that control membrane properties.
  4. Evaluate the electrochemical performance of the membranes by electrical conductivity relaxation (ECR)

 Skills which will be developed during the Master assignment:

  • Synthesis of perovskite powders and dense membranes
  • Characterization of the as-prepared dense membranes by XRD and SEM
  • Surface composition and bulk profile analysis after post annealing treatments by LEIS  and XPS
  • Evaluation of the membrane performances by ECR

For more information please contact:

Zainab Aman  (z.aman-1@utwente.nl), ECRG, ME 236B

Henny Bouwmeester (h.j.m.bouwmeester@utwente.nl), ECRG, ME 349

 [1] Hu, B.; Xia, C. Factors Influencing the Measured Surface Reaction Kinetics Parameters. Asia‐Pacific Journal of Chemical Engineering 2016, 11 (3), 327–337.

Photocatalytic degradation of glycerol in a microchannel (MSc assignment)

Background

Microreactors are well known to intensify a process. Higher conversion can be achieved by changing the reactor from a slurry reactor to a microreactor. It’s easier to determine what is happening in the channel and taking it into account due to the laminar flow. Kinetics can be identified as what is happening at the surface instead of in the bulk. Therefore, microreactors are the ideal platform to study different parameters which influence the kinetics of organic oxidation reactions. Parameters which could influence the kinetics are pH, temperature, oxygen concentration, and others. The microchannel is schematically shown in the figure below, adjusted from [1].

 

Project scope

In this project, the focus is on the influence of the light source on a photocatalytic reaction, which is the oxidation of glycerol to more valuable products. In combination with some modelling you’ll try to figure out what is happening in the channel at the catalytic wall. The experimental part will consist of conversion experiments, to measure how much is converted and into what. A second experimental part consists of fluorescence lifetime imaging microscopy, where real-time profiles of oxygen, pH, carbon dioxide and temperature can be made over the length of the channel.

Contact

For more information, feel free to contact Nicole Timmerhuis (n.a.b.timmerhuis@utwente.nl)

Reference 

[1] Rafieian, D., Driessen, R. T., Ogieglo, W., & Lammertink, R. G. (2015). Intrinsic photocatalytic assessment of reactively sputtered TiO2 films. ACS applied materials & interfaces7(16), 8727-8732.

This project can also be executed by a bachelor student, but preference is given to a master student.

Diffusio-osmosis, an engineering approach (MSc assignment)

Background

Many heterogeneous systems have mass transfer limitations near the solid-liquid interface. These limitations in the boundary layer are due to fast reaction at the wall, creating a concentration drop towards the solid. Or it could be from the velocity which is standing still near the wall due to a laminar, parabolic flow pattern in the microchannel. The main focus of this project is to overcome this mass transfer limitation by creating an osmotic flow near the solid-liquid interface in the boundary layer.

An osmotic flow is created by a pressure gradient in the liquid, which is directly proportional to the concentration gradient for non-electrolytes and to the natural logarithm of the concentration gradient for electrolytes [1]. The concentration gradient is created by the interaction between the liquid particles and solid interface, which can be repulsive or attractive. If different solid interfaces are used, alternating each other, a continuous osmotic flow can be created in the boundary layer along the wall. This is schematically shown in the figure below.

Project scope

In this project you’ll research the broader impact of diffusio-osmosis. What would be the design parameters to utilize osmotic flow for higher conversion or lower pump intensities? This could be investigated numerically. An experimental approach is also possible, where you would first come up with a possible experimental design to measure the diffusio-osmotic velocity.

Contact

For more information, feel free to contact Nicole Timmerhuis (n.a.b.timmerhuis@utwente.nl

Reference

[1] D.C. Prieve, J.L. Anderson, J.P. Ebel, M.E. Lowell, J. Fluid. Mech., 148:247-269, 1984

This project can also be executed by a bachelor student, but preference is given to a master student.

Influence of Ion Concentration on Polyelectrolyte Multilayer based Nanofiltration Membrane Performance (MSc assignment)

Introduction

In recent years a variety of micropollutants have been detected in ground- and surface water [1]. Micropollutants are small organic molecules with variable chemical properties that originate among others from industrial, medical and agricultural waste. Many of these molecules are highly toxic, carcinogenic or endocrine-disrupting compounds [2]. Even though the observed concentrations are still below drinking water guidelines, these micropollutants are potentially harmful to humans, organisms and the environment, as there is very little knowledge on longtime exposure and possible synergetic effects [3]. Traditional water treatment methods are not able to sufficiently remove these, therefore advanced separation technologies need to be developed to prevent them from accumulating in our water cycle [4].

Dense membranes used in pressure-driven filtration processes such as reverse osmosis (RO) or nanofiltration (NF) are promising techniques that have been shown to retain most micropollutants [5]. The advantage of nanofiltration membranes over reverse osmosis membranes is the reduced energy cost due to lower pressures at very comparable separation performances. A relatively young and promising method to make nanofiltration membranes is to coat a very thin and selective separation layer on top of an open porous support structure using the Layer-by-Layer (LBL) method, developed by Decher in 1997 [6]. In this method polyelectrolytes of different charged are alternately coated on top of a charged substrate. The layer formation is driven by electrostatic interactions between the polyelectrolyte chains and the entropic gain of counterion release.

Project details and outcome

In the cluster of Membrane Science and Technology these so-called Polyelectrolyte Multilayer (PEM) membranes are developed and investigated. Depending on the membrane coating conditions the structure and with that the membrane performance, solute selectivity and solvent permeability, can be changed. At the same time, it is hypothesized, that the membrane performance directly depends on the type and concentration of ions present during filtration. In addition to ion adsorption and charge screening effects, commonly observed phenomena for nanofiltration, the PEM structure might change significantly for different ions and ion concentrations, which has been recently observed in QCM-D studies of PEM swelling behavior [7].

The aim of this research is to investigate the influence of ion concentration on PEM performance related to structural changes. The focus will be on macroscopic transport measurements conducted with coated ultrafiltration membranes. Simultaneously structural characteristics of the multilayer, coated on a model surface, will be investigated. Following these detailed experimental studies, the applicability of a nanofiltration model based on the extended Nernst-Planck equation for the prediction of membrane retention accounting for ion adsorption, charge screening and structural changes shall be investigated.

Your tasks:

·         prepare and characterize PEM hollow fiber membranes

·         conduct macroscopic transport measurements

·         investigate swelling properties for different salts and salt concentrations

·         apply a transport model to describe membrane performance

For more information please contact Moritz Junker (m.a.junker@utwente.nl)

1.Aa, N. G. F. M. v. d.; Dijkman, E.; Bijlsma, L.; Emke, E.; Ven, B. M. v. d.; Nuijs, A. L. N. v.; Voogt, P. d., Drugs of Abuse and Tranquilizers in Dutch Surface Waters, Drinking Water and Wastewater - Results of Screening Monitoring 2009. National Institute for Public Health and the Environment 2010.

2.Trapido, M.; Epold, I.; Bolobajev, J.; Dulova, N., Emerging micropollutants in water/wastewater: growing demand on removal technologies. Environmental science and pollution research international 2014, 21 (21), 12217–12222.

3.Verliefde, A.; Cornelissen, E.; Amy, G.; van der Bruggen, B.; van Dijk, H., Priority organic micropollutants in water sources in Flanders and the Netherlands and assessment of removal possibilities with nanofiltration. Environmental pollution (Barking, Essex : 1987) 2007, 146 (1), 281–289.

4.Tröger, R.; Klöckner, P.; Ahrens, L.; Wiberg, K., Micropollutants in drinking water from source to tap - Method development and application of a multiresidue screening method. Science of The Total Environment 2018, 627, 1404–1432.

5.Yangali-Quintanilla, V.; Maeng, S. K.; Fujioka, T.; Kennedy, M.; Amy, G., Proposing nanofiltration as acceptable barrier for organic contaminants in water reuse. Journal of Membrane Science 2010, 362 (1), 334-345.

6.Decher, G., Fuzzy Nanoassemblies: Toward Layered Polymeric Multicomposites. Science 1997, 277 (5330), 1232–1237.

7.O’Neal, J. T.; Dai, E. Y.; Zhang, Y.; Clark, K. B.; Wilcox, K. G.; George, I. M.; Ramasamy, N. E.; Enriquez, D.; Batys, P.; Sammalkorpi, M.; Lutkenhaus, J. L., QCM-D Investigation of Swelling Behavior of Layer-by-Layer Thin Films upon Exposure to Monovalent Ions. Langmuir 2018, 34 (3), 999-1009.

Organically-modified ceramic membranes for solvent tolerant nanofiltration (BSc/MSc assignment)

Ceramic materials exhibit high thermal, chemical and mechanical stability [1]. As a result, ceramic membranes are suitable for filtration processes under harsh conditions. An interesting and upcoming separation process is nanofiltration (NF), which deals with separations on molecular level, i.e. molecules in the range of 200-1000 g mol‑1. The importance of NF processes and, by extend, of NF membranes lies on the possible recovery of valuable materials, such as transition metal catalysts and synthetic products, reuse of solvent mixtures, reduction of energy consumption for separations involving thermal treatments etc.

NF membranes must have pore sizes of approximately 1 nm or smaller [2]. Inorganic membranes, depending on the material used, show pore sizes larger than the NF limit (ca. 1 nm). On the other hand, hybrid ceramic membranes (ceramic substrates with a covalently-grafted thin polymeric layer, operating as the membrane) have tunable pore size distributions and can be used for NF applications in chemical industry. The preparation of such membranes involves the grafting of polymeric brushes on gamma-alumina (γ-Al2O3) substrates via simple condensation reactions, in solution or in vapor phase (Figure 1). A simple reaction which, depending on the polymer used, can deliver a wide range of membranes with different properties [3,4].

Figure 1: Grafting of phosphonic acid terminated polyethylene glycol on a γ-alumina porous support as an example of an organically-modified ceramic membrane.

This Bachelor assignment is focused on the development and understanding of a new and simple grafting method which would allow for easy integration to industrial levels. In this project, the candidate will benefit of the expertise and equipment of the Inorganic Membranes group to develop and assess the stability as well as the performance of hybrid membranes in different media (acidic, binary solvent mixtures etc.).  A general idea for the structure of the Bachelor assignment is provided below:

  1. Fabrication of polymer-grafted membranes on porous alumina supports. The student will develop a protocol for fabrication of hybrid ceramic membranes which can be used in lab or industrial scale.
  2. Characterize the as-prepared membranes by various techniques including contact-angle, FTIR, cyclohexane permporometry, electron microscopy, HR-MAS NMR, etc…
  3. Study the performance and stability of membranes in water-solvent mixtures. Permeability and solute rejection tests.

Skills which will be developed during the Master assignment:

  • Synthesis and understanding of the chemistry involved for fabrication of grafted NF ceramic membranes
  • Characterization of the as-prepared membranes
  •  Evaluation of the membrane performances under NF conditions (a mixture of water, solvent, and solutes)

For more information please contact:

Nikos Kyriakou (n.kyriakou@utwente.nl), Inorganic Membranes, Meander 236B

Marie-Alix Pizzoccaro (m.d.pizzoccaro@utwente.nl), Inorganic Membranes, Meander 348

Louis Winnubst (a.j.a.winnubst@utwente.nl), Inorganic Membranes, Meander 348

 [1] Tsuru, T., Inorganic porous membranes for liquid phase separation. Separation and Purification Methods, 30 (2001) 191-220.

[2] Mulder, M., Basic Principles of Membrane technology, Kluwer Academic Publishers, Dordrecht, 2nd Ed., 2004.

[3] C.R. Tanardi, R. Catana, M. Barboiu, A. Ayral, I.FJ. Vankelecom, A. Nijmeijer, L. Winnubst. Polyethyleneglycol grafting of y-alumina membranes for solvent resistant nanofiltration, Microporous Mesoporous Mater. 229 (2016) 106–116.

[4] C.R. Tanardi, I.F.J. Vankelecom, A.F.M. Pinheiro, K.K.R. Tetala, A. Nijmeijer, L. Winnubst. Solvent permeation behavior of PDMS grafted γ-alumina membranes, J. Memb. Sci. 495 (2015) 216–225.

Development of ceramic-supported 2D nanosheet membranes for Organic Solvent Nanofiltration (OSN) (MSc assignment)

Many industrial process streams are mixtures of water, solvents and other organic components. To reuse these streams, purification is required either by conventional methods (distillation) or by use of membrane technology. Membranes can facilitate to a large amounts in cleaning waste streams, which results in significant reduction in energy and contribute to a circular economy. In this project, we aim to create a new class of solvent tolerant nanofiltration membranes consisting of two-dimensional (2D) nanomaterials.

The interest on 2D nanomaterials (e.g. covalent-organic frameworks (COFs) or metal-organic frameworks (MOFs)) in membrane science and especially in OSN application is growing [1-3]. These materials, can offer control over the thickness and the pore size of the final organic layer. As such, membrane scientists theorize and in fact have observed through similar studies that 2D materials can significantly improve membrane permeabilities as well as selectivity [2]. These 2D-nanosheets-based membranes are typically prepared via in situ polymerization on a pre-functionalized support or via exfoliation of a premade 2D polymer material and subsequently coating on a ceramic support [1,3]. The first method implies covalent attachment between the inorganic surface and the organic framework and the second involves adsorption of the organic network on the ceramic support. Both can result in stable and selective membrane layers (Figure 1).

Figure 1. Overview of fabrication methods for preparation of organic framework membrane chemically (left route) or physically (right route) deposited on a ceramic surface.

In this Master assignment, the candidate will benefit of the expertise and equipment of the Inorganic Membrane group to:

  1. Preparation of ceramic-supported 2D nanosheet membranes. This method involves the preparation of a 2D polymeric material supported on a porous ceramic support via chemical or physical adsorption (Figure 1).
  2. Characterization of as-prepared membranes by various techniques like XRD, FTIR, AFM, SEM, contact angle etc.
  3. Identify key parameters that control membrane properties (thickness, adhesion to the support, etc.).
  4. Evaluate the performance of the membranes under OSN condition.

 Skills which will be developed during the Master assignment:

  • Synthesis of 2D nanomaterials and preparation of 2D nanosheet membranes
  • Characterization of the as-prepared membranes (XRD, FTIR, AFM, SEM, contact angle, DLS, etc...)
  • Evaluation of membrane performances under OSN conditions: solvents permeability and solutes rejection measurements

 For more information please contact:

Nikos Kyriakou (n.kyriakou@utwente.nl), Inorganic Membranes, Meander 236B

Marie-Alix Pizzoccaro (m.d.pizzoccaro@utwente.nl), Inorganic Membranes, Meander 348

Louis Winnubst (a.j.a.winnubst@utwente.nl), Inorganic Membranes, Meander 348

 [1] T. Nakato, J. Kawamata, S. Takagi, Inorganic nanosheets and nanosheet-based materials: Fundamentals and applications of two-dimensional systems, Nanostructure Science and Technology, Springer Japan, 2017.

[2] Hongwei Fan, Jiahui Gu, Hong Meng, Alexander Knebel, and Jürgen Caro, High-Flux Membranes Based on the Covalent Organic Framework COF-LZU1 for Selective Dye Separation by Nanofiltration Angew.Chem. Int.Ed. 2018, 57,4083 –4087.

[3] Gang Li, Kai Zhang, and Toshinori Tsuru, ACS Appl. Mater. Interfaces 2017, 9, 8433−8436.

Hybrid nanofiltration membrane fabrication and optimization on a pre-functionalized macroporous ceramic support (MSc assignment)

Many industrial process streams are comprised of solvents and small organic solutes (< 1000 g mol-1). To concentrate these solutes and purify the solvent medium, nanofiltration membranes are employed. The aim of this project is to make a stable and ultra-thin solvent resistant nanofiltration membrane by using a pre-functionalized macroporous ceramic support to direct the organic network formation. This new class of hybrid membranes will have the advantages over traditional membranes due to their ability to withstand basic/acidic conditions, organic solvents, high temperatures etc.

The candidate will benefit of the expertise and equipment of the Inorganic Membranes group to:

  1.  Fabricate a selective layer on a commercial ceramic support. This method implies the functionalization of the inorganic surfaces via an inorganic-organic linking agent [1], followed by a network formation on the pre-functionalized support [2]. The fabrication process is shown in Figure 1.
  2. Characterization of the as-prepared membranes by various techniques, such as FTIR, AFM, permporometry, electron microscopy, etc.
  3. Synthesis optimization (monomer concentration, linker density, solvents, etc...) to control membrane properties.
  4. Evaluate the performance of membranes under OSN conditions: filtration of both polar and non-polar organic solvents with model solutes

 Figure 1. Schematic representation of the synthesis of a polymeric ultra-thin membrane using a pre-functionalized porous ceramic support.

Skills which will be developed during this Master assignment which focus on synthesis and characterization:

  • Functionalization of inorganic surface with inorganic-organic linking chemistry
  • Adaptation to state-of-the-art “Click Chemistry” reactions for utilization in membrane technology
  • Characterization of the as-prepared membranes (SEM, EDX, FTIR, AFM, permporometry etc...)
  • Evaluation of membrane performances under OSN conditions (mixtures of solvents and solutes)

For more information please contact:

Nikos Kyriakou (n.kyriakou@utwente.nl), Inorganic Membranes, Meander 236B

Marie-Alix Pizzoccaro (m.d.pizzoccaro@utwente.nl), Inorganic Membranes, Meander 348

Louis Winnubst (a.j.a.winnubst@utwente.nl), Inorganic Membranes, Meander 348

 [1] A.F.M. Pinheiro, D. Hoogendoorn, A. Nijmeijer, L. Winnubst, Development of a PDMS-grafted alumina membrane and its evaluation as solvent resistant nanofiltration membrane, J. Memb. Sci. 463 (2014) 24–32. doi:10.1016/j.memsci.2014.03.050.

[2] M.F. Jimenez Solomon, Y. Bhole, A.G. Livingston, High flux hydrophobic membranes for organic solvent nanofiltration (OSN)-Interfacial polymerization, surface modification and solvent activation, J. Memb. Sci. 434 (2013) 193–203. doi:10.1016/j.memsci.2013.01.055.

Pressing PECs to Plastics: Exploring polyelectrolyte combinations for ion-exchange applications

Ameya Krishna Bysani1,2,*, Saskia Lindhoud2, Wiebe M. de Vos1

Membrane Surface Science, Membrane Science and Technology, Universiteit Twente

NanoBioPhysics, MESA+ Institute, Universiteit Twente

*a.k.bysani@utwente.nl

Keywords: Materials Science, Polyelectrolyte complex (PEC), Saloplastic, Membrane, Ion-exchange, Electrodialysis

Let me introduce you to the topic!

Polyelectrolytes (PEs) are water-soluble polymers containing fixed charges in their chains. They are particularly interesting in a scenario where oppositely charged PEs combine to form a polyelectrolyte complex (PEC). PE pairs combine in specific ratios which makes their properties extremely interesting.  Few combinations have been explored yet, and the possibilities are promising!

Films are made using these complexes, and a net charge on them allows us to explore their prospects as ion-exchange membranes (IEMs). IEMs are a class of dense semi-permeable membranes that are electrically conductive. Ideally, they allow the passage of counterions and reject co-ions.  This property is called permselectivity. Electrodialysis is used to determine the electrical resistance and other properties.

Why is this awesome?

Polyelectrolytes can be versatile, charge-controlled, complexed, and coated. Further, characteristics of PECs open many doors and their applications can be simple, inexpensive, and sustainable alternatives to several existing materials. Membranes are no exception. PEs have been used to successfully make micro-, nano-, and ultra-filtration membranes. Their use as IEMs can be extremely beneficial in desalination, water softening, and wastewater treatment to name a few!

Figure: Polyelectrolyte complexes to Ion-exchange membranes

Investigating the influence of molecular weight on the stability and performance of Asymmetric Polyelectrolyte Multilayer Membranes for micro-pollutant removal (MSc assignment)

Jurjen Regenspurg (j.a.regenspurg@utwente.nl)

Within the Membrane Surface Science Group (MSuS), part of the Membrane Science & Technology (MST) cluster of the University of Twente, The Netherlands (www.membrane.nl) we have a vacancy for a Master student.         

Project Description

New membrane materials are urgently needed to address the increasing concentrations of harmful organic micropollutants (e.g. pharmaceuticals, pesticides and plasticizers) in our surface and drinking water. These micropollutants have potential negative effects on human health and long-term health effects are still unknown for the majority of micropollutants. Conventional wastewater treatment plants (WWTPs) are not capable of fully removing micropollutants from wastewater. Using the densest available membranes micropollutants can be removed but this comes with many disadvantages, making it too costly to apply in WWTPs. 

A very promising method to tackle these micropollutants is by using polyelectrolyte multilayer membranes. Using the Layer-by-Layer (LbL) technique we are able to create polyelectrolyte multilayers (PEM). By dip coating alternatingly in polycation and polyanion solutions we build up polyelectrolyte multilayers on hollow fiber membranes. Even better membrane efficiencies are  obtained by turning to asymmetric coating of polyelectrolyte multilayers. First, a highly permeable polyelectrolyte multilayer is coated on a support membrane to close the pores. Secondly, a dense separation layer of only 4 nm in thickness is coated for selectivity. This way of coating results in asymmetric polyelectrolyte multilayer membranes that retain 98% of micropollutants while maintaining high permeabilities1.

During this project you will investigate the influence of polyelectrolyte molecular weight (Mw) on the performance of asymmetric PEM membranes. The performance of the asymmetric PEM membranes is tested by means of zeta potential, reflectometry, retention of salts and MPs, and pure water permeability measurements.

(1)          Brinke, E.; Reurink, D. M.; Achterhuis, I.; Grooth, J. De; Vos, W. M. De. Layers for Highly Efficient Micropollutant Removal. Appl. Mater. Today 2019, No. xxxx, 100471. https://doi.org/10.1016/j.apmt.2019.100471.